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Content CRITICAL STUDY OF FLUID POWERED STAGE MACHINERY IN THE UNITED STATES by Loren Robert Hufstetler A Dissertation Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (Communication - Drama) June 1978 UMI Number: DP22919 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. Dissertation Publishing UMI DP22919 Published by ProQuest LLC (2014). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 U N IV E R S IT Y O F S O U T H E R N C A L IF O R N IA T H E G R A D U A T E S C H O O L U N I V E R S I T Y P A R K L O S A N G E L E S , C A L I F O R N I A 9 0 0 0 7 This dissertation, w ritten by .............. L o r e n Ro b e r t_ Hu £ s t e 1 1 e r .................. under the direction of /l.iL. Dissertation C o m mittee, and approved by a ll its members, has been presented to and accepted by The Graduate School, in p artial fu lfillm e n t of requirements of the degree of D O C T O R O F P H I L O S O P H Y Dean Date DISSERTAT M M IT T E E Chairm an ^ .... TABLE OF CONTENTS Page LIST OF FIGURES................................... v INTRODUCTION ............................................ 1 Purpose of the Study...................... 3 Definition of Terms ...................... 5 Material Sources ............................ 6 Preview of the Remaining Chapters .... 7 N o t e s ....................................... 10 Chapter I. FUNDAMENTALS OF FLUID POWER MACHINERY . . . 12 Power Supply.................. 17 Power Transmission Elements .............. 23 Control Devices ............................ 24 Actuator Mechanisms ....................... 30 Advantages of Fluid Power.................. 33 Disadvantages of Fluid Power .............. 36 N o t e s ....................................... 39 II. HISTORICAL PRECEDENTS ....................... 41 Booth’s Theatre ............................ 41 Andrew Brown System ....................... 49 Asphelia System ............................ 53 Auditorium Theatre ....................... , 59 Hippodrome Theatre ......................... 79 War Memorial Opera House .................. 87 N o t e s ....................................... 92 III. THEATRE LIFT SYSTEMS......................... 95 Lift Functions.............................. 96 Multi-level staging ..................... 96 Scene shifting............................ 97 Special effects ......................... 98 Adaptable theatre configurations .... 99 Basic Hydraulic Lift Components......... 190 ii Chapter Page J a c k s ..................................... 100 Stabilizer mechanisms .................. 103 Power supplies............................ 105 Control features ......................... 107 Stage Lift Systems......................... 109 Orchestra lifts ......................... 109 Golden West College Walnut Street Theatre San Diego State University Main-stage lifts ....................... 122 University of Utah Hofburg Theatre MGM Grand Hotel Hesse State Theatre War Memorial Opera House Metropolitan Opera House Adaptable and modular theatre lifts . . 134 Vivian Beaumont Theatre Loeb Drama Center California State University at Long Beach California Institute of the Arts University of Texas Alternative stage lift mechanisms . . . 161 New Orleans Theatre of Performing Arts War Memorial Opera House Westmont lift system N o t e s ....................................... 175 IV. ON-STATE MACHINERY ............................ 178 Wagons and Revolves....................... 178 Munich Staatstheatre ..................... 180 New Orleans Theatre of Performing Arts..................................... 181 University of T e x a s ..................... 187 Air Bearings................................ 193 Pacific Conservatory of the Performing A r t s ....................... 202 Tyron Guthrie Theatre.................. 202 N o t e s ....................................... 211 V. OVERHEAD RIGGING SYSTEMS ..................... 213 Metromatic Loft System ..................... 21/ Synchronous Winch System .................. 222 University of California at Los Angeles Digital Control System ......... 226 iii Chapter Page Sigma Pac System............................ 230 Hydrafloat System ......................... 238 Art Drapery Studio System ................ 256 N o t e s ....................................... 271 VI. PROPOSED FLUID POWERED THEATRE FACILITY . . 274 VII. SUMMARY, CONCLUSIONS, AND SUGGESTIONS FOR FURTHER WORK.............................. 287 WORKS CONSULTED....................................... 296 iv 14 15 16 18 19 20 22 26 27 28 29 32 43 44 45 v LIST OF FIGURES Pascal's Law: Pressure Set Up in a Con fined Liquid Acts Equally in All Directions, and Always at Right Angles to the Containing Surfaces .............. Hydraulic Leverage (Multiplication of Force) and Energy Transfer (Conservation of Energy) ................................ Hydraulic Jack .............................. Hydraulic Power Supply: Basic Elements Hydraulic Accumulators: Devices for Utilizing the Potential Energy from a Descending Weight or Compressed Spring or Gas ..................................... Positive Displacement Pump ................ Variable Displacement Pump ................ Check Valves ................................ Simple Reversible Drive System ........... 4-Way Valve ................................ Electro-Hydraulic Servo Valve ........... Linear Actuators ....................... . . Booth's Theatre--Stage Plan .............. Booth's Theatre--Beneath the Stage, Trap and Platform Support Structures and Scene Storage ............................ Booth's Theatre— Horizontal Hydraulic Rams for Raising and Lowering Scenery . . . . ge 47 50 51 54 55 56 57 58 61 63 64 65 67 68 69 71 72 73 vi Conjectural Cross-Section of a Hydraulic Ram Used at Booth's Theatre— 1869-1883 . Andrew Brown System--Integrated Stage Power Layout--1875 ....................... Andrew Brown System--Hydraulic Actuator with 4:1 Travel Multiplication Blocks Andrew Brown System--Actuator Control Mechanism ................................ Asphelia Stage with Hydraulic Bridge Lifts Asphelia Stage--Hydraulic Lift Arrangement Asphelia System--Longitudinal Section . . Asphelia System--Lateral Section ......... Auditorium Theatre--Proscenium Arch with Reducing Curtain in Position ........... Auditorium Theatre--Main Floor Plan . . . Auditorium Theatre--Bridge Lifts from Mezzanine ................................ Auditorium Theatre--Bridge Lift Rams from Basement .................................. Auditorium Theatre— Bridge Lift Control Levers ..................................... Auditorium Theatre--Main Bridge Lift Pedistals ................................ Auditorium Theatre--Bridge Lift Control Valves ..................................... Auditorium Theatre--New Water Pump and Tank in Basement ......................... Auditorium Theatre--Faust Trap Lift Pedistal ................................ Auditorium Theatre— Faust Trap and Control Lever ......................... Figure Page 34. Auditorium Theatre--Horizontal Ram Curtain Lift Actuator................ 75 35. Auditorium Theatre--Hydraulic Ram Layout . . 76 36. Auditorium Theatre— Curtain Lift Control V a l v e ............................... 77 37. New York Hippodrome— Auditorium and S t a g e ................................ 80 38. New York Hippodrome--Stage and Apron Sections................................. 81 39. New York Hippodrome— View Beneath Stage . . 83 40. New York Hippodrome— Ram Equalizing Valves . 84 41. San Francisco Opera— Lighting Control P a n e l ................................... 89 42. San Francisco Opera--Grand Master Actuator . 90 43. Typical Hydraulic Stage Jack ................. 101 44. Basic Hydraulic Stage Lift.............. 104 45. Rack and Gear Stabilizer Mechanism..... 106 46. Adaptable Orchestra Pit Variations .......... 110 47. Golden West College— Hydraulic Orchestra Lift ................................... 112 48. Golden West College--Orchestra Lift Power Supply................................... 113 49. Walnut Street Theatre--Orchestra Lift System................................... 115 50. Shallow Pit Cable Stabilizing Mechanism . . 118 51. San Diego State University— Scissors Orchestra Lift...................... 119 52. San Diego State University--Lift Power Supply................................... 121 53. Lift Plan--Metropolitan Opera House .... 127 vii Figure Page 54. Metropolitan Opera House--Bridge Lift Sections..................................... 129 55. Metropolitan Opera House--Lift Guides . . . 130 56. Metropolitan Opera House--Lock Pin Actuators............................ 131 57. Metropolitan Opera House--Position Monitoring Panel ............................ 132 58. Vivian Beaumont Theatre--Adaptable Stage . . 137 59. Loeb Drama Center--Stage Combinations . . . 138 60. California State University at Long Beach-- Adaptable Theatre Stage Plan .............. 139 61. California State University at Long Beach-- Scissors Lift Sections ..................... 141 62. California Institute of the Arts— Modular Theatre..................................... 146 63. California Institute of the Arts-- Underview of Lift Platforms......... 148 64. California Institute of the Arts— Lift Plungers................................ 149 65. California Institute of the Arts— Lift Plunger with Support P i n .......... 150 66. California Institute of the Arts— Lift Platforms with Plug for Inserting Air Tube.................................. 152 67. California Institute of the Arts— Pneumatic Cylinder Access Room ........... 153 68. University of Texas— Modular Theatre .... 157 69. University of Texas— Modular Theatre Substage..................................... 158 70. University of Texas— Portable Lift Mechanism.................................. 159 71. University of Texas--Operator Installing Retaining Pin . 160 viii age 162 163 164 166 169 170 172 182 189 190 191 192 194 196 204 205 207 208 ix University of Texas--Portable Lift Integrated Hydraulic System New Orleans Theatre of Performing Arts— Rack-and-Gear Stage Lift Mechanisms . . . New Orleans Theatre of Performing Arts-- Electric Worm Gear Drive Mechanism . . . . San Francisco Opera— Screw Jack Orchestra Lift Mechanism .............................. Westmont Corp.--Cable Cylinder Lift System . Westmont Corp.--Worm-Gear, Cable-Drum Mechanism .............................. Meramec Community College--Westmont Orchestra Lift Installation .............. Hydrafloat-Cable Cylinder Assembly ......... University of Texas— Hydraulically Driven Disc Segment ................................ University of Texas— Underview of Hydraulically Driven Disc Mechanism . . . University of Texas--Hydraulically Driven Disc Drive Mechanism ....................... University of Texas— Hydraulically Driven Disc Power Supply ......................... University of Texas— Hydraulically Driven Disc Control Box ............................ Typical Air Bearing ......................... Tyron Guthrie Theatre--Air Bearing . . . . Tyron Guthrie Theatre--Air Bearing Wagon Structure ................................... Tyron Guthrie Theatre— Set Construction Framework ................................ Tyron Guthrie Theatre— Set Construction, Walls ..................................... 209 214 219 225 227 232 240 242 244 246 248 249 250 258 259 260 262 263 264 x Tyron Guthrie Theatre--Set Construction, Facings ..................................... Typical Counterweight Rigging Layout . . . . Metromatic Loft System Layout .............. Izenour Synchronous Winch System Layout . . University of California at Los Angeles- Digital Control System Panel .............. Sigma Pac System Layout ..................... Hydrafloat System Layout ..................... Uris Theatre— Cable Cylinder Installation New Orleans Theatre of Performing Arts-- Servo Valve Manifolds .................. New Orleans Theatre of Performing Arts-- Power Supply .............................. New Orleans Theatre of Performing Arts-- Hydrafloat Patch Panel .................. New Orleans Theatre of Performing Arts-- Hydrafloat Control Console .............. New Orleans Theatre of Performing Arts-- Hydrafloat Control Modules .............. Art Drapery Studio--Hydraulic Rigging Layout ....................................... Hullman Civic Center— Stage Segment Layout . Hullman Civic Center--Hydraulic Activator Installation ................................ Hullman Civic Center--Batten-Cable Installation ............................ Hullman Civic Center--Hydraulic Power Supplies ................................... Hullman Civic Center--Hydraulic Control Panel ..................................... Figure Page 109. Proposed Integrated Hydraulically Powered Mechanized Stage System .................. 275 xi INTRODUCTION One of the most important considerations to be made in the planning and outfitting of a modern theatre involves the design of the stage facility and its associated equip ment. It is usually very expensive, requires considerable developmental effort, and has a high degree of permanence once it has been put into service. Also, in these days of vigorous theatrical experimentation it is essential that the design be one that permits the greatest possible flexi bility in the types of staging and scenic effects that can be produced, and yet, with exponentially rising production and equipment costs, still accomplishes its functions with the maximum degree of efficiency and economy. To satisfy these inherently conflicting demands of flexibility, efficiency, and economy theatre designers must be thoroughly aware of every option that is available to them in making their staging layout and selecting the asso ciated equipment. Unfortunately, this is not always the case. Whereas most theatre planners are familiar enough with the more common types of equipment in use, there is still a considerable amount of confusion and lack of under standing surrounding some of the newer or less publicized methods of accomplishing the same functions. A major 1 example of this is found in the use of power operated equipment for moving scenery and adjusting staging con figurations. Most power operated stage mechanisms are driven by the means of electric motors which are coupled to their loads through mechanical linkages and are controlled by complex electronic circuitry. In a number of cases however, these electro-mechanical systems have proved to be so expensive and/or unwieldy as to make them relatively unsuitable for general theatrical usage.'*' A promising but frequently overlooked alternative to this approach is to employ the medium of fluid power, a form of motive force which has long been recognized as one of the most flexible and efficient means of transmitting power and controlling 2 motion. The concept of fluid power is certainly not new to the theatre. Before the turn of the century a number of major American and European theatres were using large water driven scenic lift systems, along with some primitive examples of hydraulic curtain movers and equipment actua- 3 tors. Unfortunately, as electrical power technology began to evolve as an effective medium for moving things, it gradually displaced the then archaic fluid power medium in most theatrical applications. Within the last two or three decades, however, the aerospace and industrial sectors have developed the state-of-the-craft in fluid power systems to a high level of sophistication, and some of this recent 2 technology has been applied to a variety of theatrical uses with the general result of increased flexibility, effi ciency, and economy over the now conventionally used elec- 4 trical forms. Also, a few new methods of moving scenery have emerged through the use of fluid power that previously 5 had not been possible with other media. Purpose of the Study The purpose of this study was to explore the use of fluid power in the American theatre in order to provide a basis for better understanding the nature of the medium as it is or may be used to drive stage equipment, and to evaluate its use in comparison with the more conventional methods of operation. Specifically, the study presented three basic problems: 1. To determine the extent that fluid power is being used as the driving medium for stage machinery in American theatres. 2. To analyze the salient advantages and shortcomings of the medium as it is used in the various systems in com parison to other methods of operation. 3. To evaluate its overall potential in the various applications as a viable alternative to the more common methods of operation. The first problem was compounded by the lack of infor mation concerning the current level of fluid power 3 development in American theatres. Although hydraulic lift systems have been used extensively in the theatre for many years they have generally been limited to conventional platform elevating applications such as orchestra lifts, etc. However, most of the development of specialized equipment has proceeded on a more-or-less experimental, prototype basis to satisfy the particular requirements of individual facilities, and in most cases little or no thought has been given to publicizing the results, or even following-up with additional development or experimenta tion. The question, then, was not to determine how many fluid power applications could be found, for that would have mostly yielded a long list of very similar lift sys tems, but rather to select appropriate, up-to-date examples of as many different kinds of applications as could be found. The second problem was limited by the lack of adequate analytical or comparative data that were available. Since the theatre as a technical institution has always been relatively poverty-stricken compared to the military- industrial sectors, it has usually not had the means to engage in basic research or to develop most of its equip ment under controlled scientific conditions. Very little standardization has existed in the field of theatre tech- 6 nology up to the present time, and in most cases the theatre facilities themselves have comprised the laboratory in which technical achievements have been developed and 7 tested. Also, much of the developmental work has been undertaken at a very pragmatic, do-it-yourself level by theatre technicians and stage personnel with limited engineering backgrounds. Consequently, much of the equip ment was never designed around optimum parameters, but was merely made to function at a tolerable level, using what ever components could be readily obtained. In addition, the available design and performance data for the stage machinery systems or their components were frequently so limited that an objective appraisal of its operating char acteristics was made very difficult. Considering these limitations, definitive evaluations of different types of theatre machinery could not be made in many cases. However, an acceptable appraisal of their relative capabilities and shortcomings was usually made possible by considering the limited data that were avail able along with theoretical projections, comparisons with similar industrial and aerospace applications, and reason able conjecture. Definition of Terms The term "fluid power" refers here to the use of con fined fluids, either liquid or gaseous, as a means of mov ing a load, and "fluid power system" refers to the total arrangement of the different components that are needed to 5 accomplish that function. Two kinds of fluid power systems are considered in this study: hydraulic and pneumatic. Hydraulic systems utilize essentially noncompressible liquids such as water or oil as the operating medium. This means that the fluid portion of the system is not a source of power but merely serves as a coupling mechanism for transferring energy from a prime mover to a load-moving g actuator. The fluid portion of a pneumatic system is gaseous, however, and thus can be compressed and stored in a pressure vessel for later use as a self-contained power source. Material Sources Since a miniscule amount has been written on the sub ject of fluid power in the theatre, most of the material for the study was derived from empirical sources, that is, from personal observations of the equipment as it is installed in various theatres around the country and from interviews with the stage personnel associated with its operation. The theatres examined in the study were selected because they were known to have equipment that was representative of the general types being studied, or possessed new or unusual features not found elsewhere. Most of the technical data for the various systems were supplied by their respective consultants, designers, and manufacturers. A limited amount of information was found 6 in technical theatre journals and texts, most of which was too general to be of much value other than as a means of locating various installations and equipment configurations 9 for later personal contacts. Similarly, the scant pub lished accounts of nonextant historical applications pro vided little more than brief commentary that a particular kind of equipment was used. However, in a few cases the sparse physical descriptions plus the random pictorial evidence was sufficient to conjecturally reconstruct a rea sonable facsimile of the original. A close study of the existing historical hydraulic installations such as the Auditorium Theatre in Chicago also provided considerable insight into the probable configurations of other period installations. Material related to current industrial fluid power technology was obtained from on-going contacts with various manufacturer’s representatives and from such technical manuals as Vickers Industrial Hydraulics Manual 935100-A. Knowledge of the aerospace aspects of fluid power was largely drawn from the writer's previous experience as a hydromechanical design and developmental engineer in the aerospace industry. Preview of the Remaining Chapters The study of fluid power as used in the modern Ameri can theatre commences with a review of some basic concepts 7 of the medium (Chapter I), with the hydraulic and pneumatic forms briefly analyzed to explain how they operate as inte grated systems. This is followed by a presentation of historical applications that show to what extent the equip ment was used in the past, how it functioned, what were its salient advantages and drawbacks, and what influence it may have had on later designs (Chapter II). The various types of stage machinery are then divided into three general categories according to their physical relationship to the stage and manner of movement. They are: 1. Lift mechanisms (Chapter III). This group is made up primarily of orchestra and stage lifts. Lift devices for adjusting staging configurations in modular and adapt able theatres are also included. 2. On-stage horizontal movement mechanisms (Chapter IV). Revolves and different wagon or slip-stage configura tions are covered in this group. 3. Overhead rigging mechanisms (Chapter V). These include spotline and batten hoist systems, vertical and horizontal curtain drives, and specialized flying devices. The discussion of the equipment in each group includes a review of the reasons why it is needed and the basic parameters under which it must operate. Current represen tative applications of the equipment are also analyzed to determine how they operate and how well they satisfy their respective performance requirements. Where appropriate, 8 possible variations in the systems to improve their per formance are also considered. Most of these applications are then compared to systems driven by other, nonfluid media, with appropriate examples included to illustrate some of their relative merits and deficiencies. The basic types of fluid power equipment are then evaluated in com parison to equipment driven by other media as well as in terms of their inherent capability to accomplish their intended functions. A theoretical projection is also made to demonstrate the potential capabilities of future sys tems that have not yet been developed but are within the grasp of our current technology (Chapter VI). A final summary is then presented along with suggestions for fur ther study concerning the various options that are avail able to the designers and users of stage machinery (Chap ter VII) . 9 Notes The Izenour Synchronous Winch System (first intro duced at Hofstra College, New York, 1959) provides a graph ic example of a widely heralded type of stage machinery that has not been generally accepted among theatre practi tioners because its expense and operational difficulties have been shown to outweigh its many functional advantages. Similarly, the Metromatic Loft System (installed at the Metropolitan Opera House, Lincoln Center, New York, 1966) has not yet been accepted as a practical alternative to conventional rigging systems, even among affluent theatre builders. Its principle fluid counterpart, the Hydrafloat System (as installed at the New Orleans Theatre of Perform ing Arts, 1973) also has not attracted a host of eager new customers, but it promises to be a comparatively simpler and less costly form of automatic, remote controlled batten rigging system. These systems are discussed at length in chap. 4. 2 Vickers Industrial Hydraulics Manual 935100-A (Troy, Michigan: Sperry Rand Corp., 1970), preface. There is general agreement in the aerospace and industrial machine industries that, in terms of cost, weight, and efficiency, fluid power systems have usually proved to be more advan tageous than electrically or mechanically driven systems in precisely controlling the movement of large loads over moderate distances. 3 Discussions of historical fluid power applications are included in chaps. 2, 3 and 5. 4 The Hydrafloat System, discussed in chap. 4, again provides a good example of the application of recent indus trial and aerospace technology to theatre machinery. 5 This is exemplified by the use of air bearings to support heavy stage wagons that could not practically be carried with conventional casters. Their use is covered in chap. 3. 6 Olaf Soot, "Engineering Concepts in Stage Equipment," Theatre Design and Technology, 6 (October 1966), 13. ^Soot, p . 11. 10 g Vickers Industrial, pp. 1-4. 9 The most useful technical theatre journal for this study was Theatre Design and Technology. The primary jour nals used in locating information on historical applica tions were Scientific American, American Architect and Building News, Harpers Weekly, and Appleton's Journal. "^This was particularly the case with the conjectural reconstruction of the machinery at Booth's Theatre (1869- 83), which is discussed in chap. 2. "^The hydraulic machinery at the Auditorium Theatre is considered in detail in chap. 2. 11 CHAPTER I FUNDAMENTALS OF FLUID POWER MACHINERY Discussions about power driven machinery usually are not concerned so much with how the initial motive power is generated as how it is transmitted and applied to the mechanism. In most applications the initial power comes from somewhere else in the form of electricity, which must then be converted by some means into a mechanical force capable of doing useful work. In the case of some electri cal power transmission devices all that is needed to accom plish this is to connect the wires from the power source to an electric motor through the appropriate control circuitry. The motor then converts the electrical energy into a ro tating motion. Most kinds of stage equipment, however, require an additional mechanism to convert the rotation of the motor into a more suitable form of motion for its load. Mechanical linkages are the usual method. Fluid power is another. All of the hydraulic mechanisms that will be con sidered in this study operate primarily under the principle of hydrostatics, the science of liquids under pressure as opposed to hydrodynamics, the science of liquids in motion.'1 ' With these mechanisms power is transferred from a 12 prime mover to a load through changes in potential energy, that is, through energy that is first built-up within the hydraulic fluid by a pump and then released in an actuator rather than by changes in kinetic energy, that is, the forces generated by a moving liquid impinging on an object 2 such as a turbine impeller. The basic precept under which all hydrostatic mechan isms operate is Pascal's Law, which was set down in 1650 and states that "pressure set up in a confined liquid acts equally in all directions and always at right angles to the 3 containing surfaces" (Figure 1). This law was first put into a practical application in 1795 when Joseph Bramah 4 created a functional hydraulic press. With it he demon strated that a force applied to a small area of a confined liquid would produce a proportionally greater force on a larger area, creating a significant mechanical advantage, or power amplification (Figure 2). From this example it is an easy step to apply Pascal's principle to the operation of a simple hydraulic jack (Figure 3), which incorporates all of the elements of a basic hydraulic system. From an operational standpoint most hydraulic or pneumatic systems can be divided into four logical ele ments: (1) the power supply, (2) the power transmission element, (3) the control device, and (4) the actuator mechanism.^ 13 Co n t a in e r . f /l l e o n /th MOM- C O M P R E S S I & C C L /Q U ! O A to POUND FORCE APPLIED TO A ONE SQUARE INCH SURFACE AREA • • • P R O D U C E S /O P O U N D S OP FOR.CE O N E V E R Y S O U A R E /fJCH O F W E CONTAINER W A L L . I F THE A R EA O F THE BOTTOM 1 3 \ 2 0 S O U A R E iN C H E S THEN / T R E C E IV E S A E O O P O U N O P U S H . F IG U R E . I PASCAL *5 LAW \ PR ESSU R E SET UP i n a C O N F IN E D l i q u i d a c t s E q u a l l y i n a l l d ir e c t io n s , a n d a l w a y s A T R IG H T ANGLES t o t h e c o n t a in in g s u r f a c e s 14 A lO Po u n d f o r c e o n a f souA r b in c h p is t o n DEVELOPS A PRESSURE OP /O POUNDS PGR SQUARE INCH (P S l) THROUGHOUT THE C O NTAINER . THIS /O PS! PRESSURE PRODUCES A fOO POUND f o r c e o n a lO s o u A RE INCH P IS TO N . / / N C H JO INCHES to o IN C H POUNDS OF ENERGY ( to POUNDS MOVED IO INCHES. ) EXER TED O N THE SMALL P IS T O N ■ ■ ■ ISTRANSFERREO TO THE LARGE PISTON ( too POONOS MOVED / INCH). IO POUND FORCE \ iOO ROUND FO &C& L JO INCHES IO F E E T m e c h a n ic a l EQUIVALENT f i g u z e 2 / INCH I F O O T H YD R A U LIC L E V E R A G E (MULTIPLICATION o f f o r c e ) AND E N E R G Y T R A N S F E P (CONSERVATION OF ENERGY) 10 hi 0! J9 LL I < 0 8 KJ vl a 5 5i * VJ 3 16 Power Supply Hydraulic power supplies come in all sizes, shapes, and configurations, but the basic components include a prime mover (usually an electric motor) to which a pump is connected, and a reservoir which supplies fluid to the pump and receives that which is returned from other parts of the system. In addition, a gauge is usually required to measure the pump output pressure, a relief valve to prevent system overpressurization, a by-pass or unloading valve for directly returning the output flow of the pump back to the reservoir without being applied to the load, and some sort of filtration device. Occasionally an oil cooler might be necessary along with an over-temperature protection mechan ism (Figure 4). Sometimes an accumulator, which is a device for storing energy with a spring or volume of com- 6 pressed gas, might be included (Figure 5). The heart of the power supply is the hydraulic pump. Although hydraulic pumps also come in a wide variety of sizes, shapes, and configurations, the kind that is most commonly used in simple hydraulic systems is the positive displacement type. With these units the pumping element moves a fixed amount of fluid from the inlet to the outlet port with each pumping cycle so that, at a constant oper ating speed, the output flow is the same regardless of the pressure that is generated. Perhaps the simplest type of positive displacement unit is the gear pump (Figure 6). 17 Uj U) ^ Uj 18 <0 $ 3 9> Jki < o J9 k • j < 0 < J ) 5 UJ ( y o Sr <¥ k v 0 kl W r . S § w c£j ^ Uj 5 ^ * ^ q ° Uj ^ c o 0 ( A C j ^ S X * ® 5 g , k ) ^ Si ">15 k ss 5 0 ^ h o * 5 «j ^ ^ v ^ H ^ < i : c j ' v u s ; r ? § Uj s to ,<0 Q k — v ' ° 8 ui ^ V) U] ku QJ ^ ^ sr «c ^£1 v » S 5! k) c o V) <0 <0 <n£ ky ^ L | » k> I Ch Q) C l V) k ly »l M lU 3 £<> V] I \o U j 1 1 III 'M£i CO ^ JO Kjn < y U ) y CO § kj * 0 Uj ft? o 19 HYDR.flUL!C ACCUMULATORS : pevices Foe. utilizing the p o t e n t i a l ENEP&Y P P O A O a DESCENDING w eight O E COMPEES5E D SPFfNG O E G/\S VACUUM /S G E N E P A TE O E T 7 //E IN L E T P O R T- * AS F L U ID I A P/C/CED U P IN THE C4M T /E S DRIVEN GEAR. DR. W E G E A P O £> m M OUTLET C h U O H /= > /Z < £ S > S U R .E ) F L U / D I S C A R R I E D G R O U N D T H E H o u s / N G _____ AND DU SUED OUT THE HI OH PRESSURE PORT G >Y THE FLUID COMING /N BEHIND IT. FIGURE 6 P O S IT IV E D IS P L A C E M E N T P U M P (& E A E TYPE) With this configuration the gears, which are turned by the drive motor, pick up fluid at the inlet port and carry it between their teeth around the housing to the outlet port where most of it is pushed out by the fluid coming in behind it. A small amount of leakage from the high pres sure area of the pumping chamber back to the low pressure area (internal leakage) is inevitable because of the imper fect meshing of the gears and the necessary clearances 7 between the gears and the housing. Except for internal leakage the amount of fluid pumped is proportional to the speed of the drive motor, and if the pressure generated at the outlet port should become blocked, either by the sudden stopping of a moving actuator or by the closing of a valve, then the continuous flow of incoming fluid would rapidly force the outlet pressure up to a point where either the drive motor would stall, something would break, or a con veniently placed relief valve would open. Another method for handling the inevitable variations in flow demand is to use a variable displacement type of 3 pump. This is usually a piston type unit (Figure 7) which has a built-in mechanism that can rapidly change the piston stroke to vary the pumping capacity. A regulating device can then be attached to this mechanism which proportionally increases the outlet flow rate whenever the outlet pressure falls below a predetermined value. This type of pressure compensating arrangement makes it possible to automatically 21 T H E C Y L J N D E K B L O C H , P /S T O N A S S e r /U ) E L Y A h ) D T H E ' P P o N T H A L F O F T H E : W O B B L E P L A r e S H A P I N G R O T A T E W i t h T H E D fL J V E S H A F T . T H E P L A T E A N D P E A N H A L F O F T H E W O B B L E P L A T E A R E F H C E D Teo T H E F > U N \P H O L > S /H <5, T H E p / S T O N S A R E W I T H D R A W N P N O M r H E C V i / A / 0 £ / 2 E l . O C k B O R . E O N T H E H . F T H f i E T ETHC>K£ ■ • • V A L V E P L A T E S L O T I N L E T P O R .T V ( S U C T IO N ) O U T L E T P O R T (p r e s s u r e ) 4- v> v 2 CVLINDEP BLOCK AND ARE PU&HEO BACK IN ON THE EXTEND ST/ROtCE. O P / V E W o b b l e PLATE B E A K INC -«— S T R O K E L E N G T H max/mum wobble P late angle zer o w o b b l e p l a t e a n g le (MAnmuaa P/SToN STROKE) . (zepo P/STON St/Zo n e ) F I G U X . F 7 \JARM3 LE DI3 PLAcEMeslr PUMP ( in-line f’/STo* TYPE' ) 22 10 maintain the outlet pressure within predetermined limits while varying the outlet flow rate to meet whatever demand may occur up to its full pumping capacity. With the use of one of these pumps the power supply can be left running continually to provide a constant source of pressure to the control valves of several different actuators in an inte grated system. In theatrical applications several differ ent mechanisms could be moved either simultaneously or sequentially during a production with the use of only one remotely located power supply. This type of pump is very rugged and durable but is more costly than the fixed dis placement type. Power Transmission Elements The power transmission part of the system is made up of those items that are used to transport the power from the pump to the actuator. This includes the fluid medium as well as the conduit. Three basic kinds of fluids are used in hydraulic 9 systems. The oldest and least expensive is water. It is also the least desirable because of its poor lubricity, corrosive tendencies, and limited temperature range. Petroleum oil is the most commonly used base for hydraulic fluid in industrial and military applications. It is moderately priced, has good lubricity and oxidation resis tance, and has reasonable stability and viscosity 23 characteristics. The third category is made up of the three types of fire resistant fluids: water-glycols, water-oil emulsions, and synthetics. The water-glycols and water-oil emulsions are not much more expensive than petro leum oil and offer good fire resistance, but they are rela tively susceptible to foaming, contamination, and insta bility due to water evaporation. Synthetic fire-resistant fluids are laboratory synthesized chemicals from either the phosphate ester or chlorinated hydrocarbon groups. They do not support combustion, have excellent lubrication charac teristics, are noncorrosive, and perform well at high operating temperatures. However, they are very costly, harmful to most organic materials, and very irritating to the skin. Consequently, they are not recommended for theatrical applications.^ The conducting lines in a fluid power system usually consist of rigid pipe or tubing for fixed connections, or of high pressure hose for flexible connections or for damp ing vibrations and fluid-born noise. Most pipe and tube fittings and some of the sealing components are also included in this segment of a system. Control Devices Most control mechanisms that are used in fluid power systems consist of valves that fall into one or more of three general groups. The first group is made up of 24 metering or flow control valves. They work in principle like the garden variety water faucet to regulate the rate of flow passing through a circuit. Next are the directional valves. Valves in this group range from simple one-way or check valves (Figure 8), which allow flow through a passage in one direction only, to the versatile four-way valves which can be used to switch sys tem pressure from one actuator port to another while open ing the opposite port to return (Figure 9).^ Among the four-way valves the spool-type is probably the most common (Figure 10). With this arrangement the spool is slid back and forth in a close-fitting bore to open the required passages. Because of the required spool-bore clearance and the need for lubrication a small amount of internal leakage from the pressure to the return areas must be allowed. In addition to their directional control function most valves in this group can also be made with a metering capability. The third group is made up of pressure regulating valves, which include relief valves, pressure reducing valves, unloading valves, sequence valves, and brake valves. One of the most sophisticated of all hydraulic compo nents is the four-way, spool-type, electro-hydraulic servo valve (Figure 11). It is basically an electrically con trolled directional valve that can also be made to regulate flow or pressure functions. It is possible with this type of valve to precisely control the positioning, velocity, 25 FFFE FLO IAJ AS &ALl_ JS P U S H £ & A W AV F/ZOM SE A T W W ^Mfa R E V E R S E Ft O W &LOC/<CFO Ais BALL /S Fi/SHEQ AGA//VST SEAT JM -L //V E C H EC K V A L V E ( BALL T Y P E ) OUT f r . e e FLOW N O F L O W right Angle check, valve ( poppet t y p e } FJG U & E 8 C H E C H VALVES [ o n e - w h y, p / b b c t i o n ^ l Co NTB oB) 26 ( 7 ) / A E T T E R / N G V A L V E ( V P P i A B L E — y ORificE P l o w control) P F S T P l C T S E L O V U T O R E G U L A T E T H E : R A T E O F A C T U A T O R . P I S T O N T R . A V E E - ( b \ R E L I E F I / / ) L l / E ( P R E S S U R E C O N T R O L ) L I M I T S R E E S S U R E T O T H E A C T U A T O R . 6 V CN V E R T / N G E X C E S S R U M R R / O i N S A C K T O T H E R E S E R V O I R . P> U AA O (3) 4- - IT/A T V A L V E---- ( D I R E C T I O N A L C O N T R O L ) C O N N E C T S T H E p r e s s u r e l a n e t o t h e h e a d E N D O P t h e A C T U A T /H 6 C Y C / H O E R A N D T H E I R O D E N D T O T H E R E T U R N L / A / E ~ T H E R / S T O N H o O Ex TEHOS ^"^NsZZS % ► 3S532Z2(5^Effi2SiS 3 J vh—1 pst&sa. Actuating C Y L t H O E R . S U C T IO N L I N E Li L_1 (LETOFLN L f v e S Z Z 2 2 Z Z T - P U A A P ( 5 ) V A L U E P O S I T I O N F Z E V E R . S E O T O C O H A /E C T T H E P R E S S U R E L I N E T O T H E R O D E A / O O F T H E C Y L f N O E R . A A /O T h e H E A D E N D T O Th e R E T U R N C / N E ~ T H E R I S T O N R O D R E T R A C T S . A C T U A T I N G CYLINDER S U C T /o H L / N E RELIEF V A L U E 4--INAY VALUE VVV22/S2& 111 1 R E S E R . I / O I FS. f = / G u a e 9 S/AAPLE &EV£’ &S/&L£ DRIVE SYSTEM 27 L.flfiJDS ON Tver S£./o/*/& valvz' spool & L O C A C 7 ~ P £ P /L O t A / E Z e p i A / p ; £ W P O R T S A 4 - & A M D & E T I A J M T N £ P £ P S S U # t / AND R E T U R N L/a/^5 SPOOL. S L/O TO 77 /6T L&FT OPEf/S PPESSURE TO Po r t A a n d p o r t & T o R E T U R N /Z.ETTC'R.N SPOO C SlL/O TO THE SGE&T OP£TaJ S F*Ges>sufizE 7- 0 po/zr & aa/o POP.T A r o f^^TUPAj f c e r u p N F /G U R E / O & -W A Y VALVE (spool typej directional control) 28 (S) SRRJNC& BALF/VCE t h e s p o o l, / n t h e CENTER POSITION (A //T H F O R T S A $ & B LO C K ED TH£ FLAP PEE. IS CENTE/ZED B E T W E E N THE N O Z Z L E S SO THAT FLOW FROM BOTH NOZZLES / S THE SAME, PRODUCING E Q U A L F E E S 5 ( J P E S I N THE N O Z Z L E L/NE£. ) A S M A L L D / F F E F E a J T / A L C U R R E N T A P P L I E O T O 7~H/E T O Z G l U E M O T O R - M o U E S THE F L A P P E D O N E W A Y t h e o T t / E ' R . R E O U C . / N G T H E F L O W A T O N E N O Z Z L E A N D i n c r e a s i n g / T A T T / / E o t h e r T O p r o d u c e u n b a la n c e d p r e s s u r e s /N T H L E l / n e s a n d A T T H E s p o o l . E N O S j ( A /H /C H M O V E S T H E s p o o l a g a i n s t t h e f o r c e o f t h e , C E a / T E R / A / Q SPRINGS TO o p e n p o r t s a 4 b. E L E C T R O -M /J G N E T /C T O R Q U E /v \o to p fo P S / / OOOPSI 500PS/ FIXED O F ! F fCES L J A n /T p l o w f r o n \ t h e M A I N P R E S S U R E S O U R C E , R E D U C IN G P R E S S U R E / N THE F L A P P E R . N O 'Z .Z .L E U a/^S. (?) THE SPOOL IS CONNECTED t o t h e FLAPPER. F ul CfeuaA f which PROVIDES MCCHAN/CAL FEEDBACK., NiAKtNd? THE VA Ll/E OPENING PROPORTIONAL TO t h e e l e c t r ic a l IN POT CURRENT. FIGURE U ELECTEO - HVDR.AUL 1C S E E. VO VALl/E ( FLAPPED TYPB, D /T L E C T (O M /\L A N O F L O W C O K fTLR O L.) 29 and acceleration rate of an actuator mechanism. Servo- valves are fairly reliable and durable but are relatively expensive. Also, they are very sensitive to fluid contam- 12 ination and must be provided with very fine filtration. Actuator Mechanisms Actuator mechanisms for the fluid power media are usually grouped into two basic classifications: rotating and linear. The most common types of rotating actuators are hydraulic and pneumatic motors. Most fluid power motors are very similar in construction to their pump 13 counterparts. They also come in many configurations such as gear, lobe, vane, piston, rotor, and so forth. Hydrau lic motors can be made to put out an incredible amount of torque from very low to very high speeds. Unfortunately, some of them (particularly the high pressure piston types) may be too noisy for on-stage applications. Most of them also have a tendency to slip slightly while holding a load in a static position because of their built-in internal leakage characteristics. Linear actuators, which are nothing more than hydrau lic cylinders, come in two basic categories: single-acting cylinders or rams (Figure 12A), which are driven in one direction only and rely upon gravity or some other external force to retract the plunger; and double-acting cylinders, which drive a piston in both directions. Most 30 double-acting cylinders (Figure 12B) move more slowly in the extend direction of travel than in retraction because of the volume that is taken up by the piston rod, and con versely, the force exerted on the head-end is greater than that on the rod-end by the same ratio. This differential force-rate characteristic is often used to advantage where it is desirable to combine a large actuating force in one direction with a rapid return stroke. Where uniform forces and rates of travel in each direction are desired the prob lem can be resolved by using a balanced actuator (Figure 12C), in which a dummy rod is added to the head-end of the cylinder. This arrangement adds another rod's length to the actuator, which must be accounted for in the installa- t ion . There are two important considerations that must be taken into account in the use of hydraulic cylinders. The first is that their working stroke is limited to the maxi mum travel that the piston can make in the cylinder. This can be a problem in applications where a load must be moved a long distance. For example, in order to use a hydraulic cylinder to power a rigging system with a sixty foot lift it would be necessary either to use a sixty foot cylinder (with an extra sixty feet of space allowed for the rod extension), or to use a cylinder with a shorter stroke coupled to a multiple purchase arrangement which, in turn, 14 would be attached to the lift cable assembly. O I o 1 ECU/\/C£ft (PAM) C YL/A/DET/Z I W/PEP. R.ING PL UN GEE SEAL A ~ S/AJGLE ACT/NG CYUMDGG. (PAM) R.OQ P / S T O N HEAD EAJD P/STON Ge /)L B> ~ D / P P P P E N T / A D (ONE P/STON Poo) C ^ b a l a n c e d (TWO PODS) double: hct/ ng cyl/ a/ dg/ zs E l G U / z e /2 L /M E /I/Z A C TU A TO R S (C Y L IN D E R S OR R ftM S ) 32 The second consideration is leakage. The only leakage path in a simple ram is across the piston seal. Double- acting cylinders, however, have two possible leakage paths: at the external sealing glands and internally across the piston seal. With the use of modern loaded Teflon seals cylinder leakage in many applications can be effectively eliminated. Advantages of Fluid Power In comparing the relevant features of the electrical, mechanical, and fluid power transmission media it is evi dent that fluid power offers some decided advantages as well as a few obvious drawbacks. One of the most important aspects of fluid power tech nology is the ease and accuracy in which movement can be controlled. Huge power amplifications with constant force or torque outputs can be produced with very simple mechan isms and the movement and positioning of massive loads can be precisely regulated with the expenditure of very little energy. Fluid power systems are also generally very straightforward and flexible. They usually have fewer mov ing parts and fewer areas of wear than other types of sys tems made for the same purpose, and they can usually be designed with pre-engineered components that may be easily installed in simple structures. And since the various com ponents are connected by piping or hoses they can be placed 33 at the most convenient locations rather than where mechan ical linkages dictate. This inherent flexibility is enhanced by the possibility of using one central power supply to serve many actuators, each operating at different pressures and flow rates if necessary, and controlled by independent, remotely positioned valves. In general, hydraulic power systems are capable of efficiently trans mitting power farther than equivalent electro-mechanical 16 systems, but not as far as purely electrical systems. The great pressure density that can be obtained in a hydraulic actuator, plus its inherently compact configura tion makes it possible to concentrate much more power with in a limited volume than with other methods. Electric motors, for instance, can only generate an equivalent of about 200 psi in tractive power compared to the 3,000 psi 17 that is frequently employed in hydraulic equipment. This is why systems in industrial and aerospace applications that require the expenditure of great energy within a small space are invariably hydraulic. The energy compactness of a hydraulic system can also be important where the weight and bulk of the machinery is a factor. In general, hydraulic motors tend to be much smaller and lighter than electric motors of a comparable output, particularly in sizes above 1 horsepower. In 3,000 psi systems they usually deliver more than 1 horse power per pound and horsepower-to-weight ratios up to 2.5 34 18 are not uncommon. This may be of particular significance in theatrical applications where the machinery must be mounted overhead on independent supporting members or on basic structures within the facility that may have to be 19 especially designed to carry the additional load. In some applications the cost savings of the supporting struc ture by itself may be sufficient to economically justify the use of hydraulic components. In addition to their weight and power advantages, hydraulic motors also exhibit excellent controlled full load starting characteristics and provide nearly constant torque throughout their entire speed range. Also, they can be reversed while at full speed or stalled at full load without damage to the system, and they can be instantly accelerated and stopped under no-load conditions because of their extremely high ratio of torque to inertia and the lack of counter electro-motive-force that is characteristic 20 in electric motors. Furthermore, because of the relative incompressibility of the fluid medium they provide a more rigid support for heavy or springy loads. Linear actuators offer the luxury of exceptionally smooth, quiet operation while generating incredible forces. Their acceleration rate and operating speed can also be closely regulated, and they have a built-in braking and holding feature, which is accomplished merely by closing off a valve at the outlet port. 35 Through the use of electro-hydraulic servo valves hydraulic actuators can be operated with automatic, pre determined velocity and acceleration control, and can be set to stop within very narrow travel limits. In addition, the electromagnetic control feature permits the use of compact, remotely located control panels which carry only a safe, low control voltage rather than the full power of the actuator mechanisms. The heat dissipation characteristics of most hydraulic components are also superior to comparable electrical devices because the moving hydraulic fluid acts as an excellent conductor to carry the heat away from the working mechanisms. This aids in keeping the work areas cooler and eliminates the need for heat absorbing masses, aside from the possible use of an oil cooler which could be installed in any conveniently isolated location. Disadvantages of Fluid Power The fact that electro-mechanical systems continue to power the great majority of stage mechanisms is moot evi dence that the fluid power medium still suffers from major disadvantages. Perhaps the biggest functional problem in the use of hydraulic machinery is, as it has always been, that of leakage. Leaks are inevitable in any hydraulic system, particularly during the set-up period or in changes of configuration. Spilled hydraulic fluids are messy and 36 slippery, which can be hazardous. In the event of a rup ture in a high pressure element of a system a resulting high velocity stream of oil could be damaging to adjacent equipment or set-pieces or to persons standing nearby. This condition is particularly hazardous when petroleum oils are used because of their flammability. However, the danger of fire from leakage in a hydraulic system is probably no more acute than from short circuits in a com parable electrical system. Internal leakage within a hydraulic system, either from worn or malfunctioning parts or from partly open metering valves, could also create problems by robbing needed power from the actuators, or dissipating enough kinetic energy to overheat the system. Hydraulic actuators may also tend to slip slightly under long durations of static loading, and some hydraulic motors and open-center servo systems may slip sufficiently to require a separate mechanical holding device. Noise is also a factor in theatrical applications, as has been previously mentioned, along with the problem of limited piston travel in linear actuators. Fluid contami nation is another consideration that must be contended with in most hydraulic systems, particularly in those with electro-mechanical servo mechanisms. The length of travel of an actuator also may occasionally pose a problem with fluid powered machinery, but this is also common to many 37 electro-mechanical devices . With pneumatic systems these problems are compounded by the compressibility of the fluid media, which tends to produce jump starts, piston bounce, and explosive condi tions if a system is broken into while under pressure. Like all physical systems, the greater the complexity of a fluid power mechanism, the greater will be the initial expense as well as the costs of operating and maintaining it. It is difficult to assess these relative costs, but most fluid power systems have generally tended to be very 21 competitive with their electro-mechanical counterparts. 38 Notes ^Vickers Mobile Hydraulics Manual M-2990-S (Troy, Michigan: Sperry Rand Corp., 1967), p. 2. 2 Vickers Mobile, p . 2. 3 Charles S. Hedges, Industrial Fluid Power (Dallas: Womack Machine Supply Co., 1968), p. 10. 4 Robert Gordon Blaine, Hydraulic Machinery (London: E. and F. N. Spon, Ltd., 1897), p. 1. 5 George R. Keller, Hydraulic Systems Analysis (Cleve land: Industrial Publishing Co., 1969), p. 5. 6 Vickers Industrial, pp. 12-1-6. Caution must be exercised in the use of spring or gas charged accumulators in a hydraulic system because of the potentially explosive nature of the highly compressed spring or gas. 7 In practical usage the internal leakage in most gear pumps is of such a magnitude that the maximum working pressure is limited to about 500 to 1,000 psi. Vane pumps, which characteristically exhibit less internal leakage, are frequently used in applications of the 1,000 to 2,000 psi range and piston type units are usually employed in systems with higher working pressures, commonly in the 2,000 to 4,500 psi range. g For a more detailed description of the operation of fixed and variable displacement pumps refer to Vickers Industrial, chap. 11. 9 Vickers Industrial, chap. 3. "*"^The use of synthetic fluids is usually limited to applications where any risk of fire would be catastrophic, such as in commercial airline service, and then it must be totally isolated from general public exposure. This is not possible in the theatre where the performers, technicians, and audience could be exposed to harmful vapors emitting from a cracked high pressure line in a stage mechanism. "^Vickers Industrial, chap. 7. 39 12 Vickers Industrial, chap. 8 and Keller, chap. 11. The size of the flapper nozzles in most servo valves is so small that filtration on the order of 5 to 15 y is usually required to keep them from being clogged by particle con taminants . 13 Vickers Industrial, chap. 6. Many hydraulic motors and pumps are identically constructed except for the con figuration and timing positions of their valve plates. 14 Another method, which has been successfully employed in theatrical applications, is to use a cable-cylinder arrangement. This type of mechanism is discussed at length in chaps. 4 and 5. 15 In the last ten or fifteen years the use of Fluoro- plastic (Teflon) materials has significantly reduced the nominal leakage rates in most dynamic seal applications (applications where the seals slide against a moving me chanical part). 16 Keller, p. 3. '*'^Keller , p . 3 . "^Keller, p. 3. 19 The weight-saving aspect of hydraulic machinery is covered in greater detail in the discussion of the Hydra- float System in chap. 4 below. 90 Keller, p. 3. 21 Vickers Mobile, p. 21. 40 CHAPTER II HISTORICAL PRECEDENTS Booth’s Theatre Although hydraulic machinery of one sort or another had been in frequent usage in commercial and industrial applications for a large part of the nineteenth century/ the first significant application of fluid power mechanisms 2 in the American theatre did not occur until 1869 when Edwin Booth built a splendid new theatre that was more elaborate and technically advanced than any other ever before seen in this country. He wanted a theatre in which multi-set classical productions could be mounted with the greatest sense of realism that was then physically possible. To do this he ’’availed himself of the latest inventions and 3 devices in producing scenic effects,” and had his stage constructed so that the scenes worked altogether by machinery, which were lifted from below, by means so carefully and accurately adjusted that the scene almost noise lessly and with perfect precision, glides upward into its place.^ The seventy-five by fifty-five foot stage at Booth's Theatre was similar in most respects to the other major theatres of the time except that it incorporated a system of four narrow bridges or "sinks” on which free-standing 41 5 scenery could be raised into position from a substage storage area. The sinks, which were about three feet wide by about thirty-nine feet long, spanned the width of the center-stage area and extended from just behind the curtain- line up the stage on about an eight foot spacing. In addi tion, four three by seven foot traps were located in a dia mond shaped pattern behind the second, third, and fourth 6 sinks (Figure 13). The vertically moving platform struc tures which serviced the sinks and traps were located in the substage area, thirty feet below the level of the 7 stage (Figure 14). These were raised and lowered by means of large horizontally mounted hydraulic rams of which there was "a long formidable row” (Figure 15).** The rams were "hidden away in the subterranean caverns” beneath the sub stage floor, under the bridge and platform structures. They drew their power from the water stored in large 9 reservoirs at the top of the building. This arrangement provided about 120 feet of static head of water, which is equivalent to a working pressure of just over 50 psi.^ Assuming the operator depicted in Figure 15 to be about five feet, six inches tall, then the stroke of the ram would have been approximately six feet in length (scaled from the spacing of the travel-limit stops on the control valve override actuating rod) and the bore would have been about two feet in diameter. With a drive wheel mechanical advantage of approximately five-to-one through the rack and 42 S GR.OOVG SETS* 4 S/A/K& £Ufc7~fl/AJ A/ A / A - F / & u / z e / 3 S O O T /-/' S TM E4TR.E - /=>;&*/ 43 F I G U R E / + B O O T H 'S T H E /)T /2 £ - & £ A /£ /tr// s r/)0£ , r/e /)/° and pla^o& m S u p p o / s t srtsucru/zes a n d scstkje sTDP-pas .. Oi \ ', S j . v \ *' *.— j j [ ' - i«. * ■ * > * j A ^ Uy y . y.r"'l >r^ " • ' j‘ ,i^i* ; V ^ > . T i ,> > *1 m <*» y J * - *' » r ' v . ~ t: , / f: j » T ^ i , i f ? v I* R ' ' * i \ • * I - \ -V *^v 1 , £ 1 t -A ? ^ ■ ’5^. / - V ‘:t fif5 • ‘ > / '!..•# N ' ? 1 l - Will • . « • » • » • . •■; . » < ,V- llIlM M / r rl f /.jriS & J • 4, • . - ' * /!^i u* - ? f y * * i » » - i ! f / . J </1 f£jt I * W j j g 4 : r ’ sj 4 jT/ii •’ ■v\ N t ..♦ • c-v.V>1 iP ; \ J -- f i : 1 p i r r ^ V * / ! * 1 ' i ' ^ ■art* • y I • • tl \ V . I V y - . “ ' *# * *v ‘ ne^tsf y^~ /- -%V . • rt#n |f»*V * ♦ u \ )\ A f t BO O TH'S THE AT RLE — H O IS -IZ O N T R L HYO/ZRUL/C /£HMS> FO£_ £./R/%/n G — r n d l o w f / s / N O & c e N E re Y gear drive mechanism (Figure 16), and a friction loss of about twenty percent, the lifting capability of each hydraulic ram is conservatively calculated to have been almost two tons through the thirty foot travel, less the uncounterbalanced weight of the lift structures. This machinery, coupled with a full fly gallery (one of the first in the country) permitted Booth to initiate the use of three-dimensional, changeable scenery on a grand scale within his fifty by fifty-five foot proscenium open ing. It was noted that in this theatre "columns and monu ments and projections of buildings were real (that is, pasteboard or canvas) and not painted, and could be "sunk below the surface or lifted into the mysterious 12 spaces of the air with magical swiftness." The success of Booth's hydraulic machinery has been attested to by various commentators of the time as well as by the tacit evidence of the tremendous amount and variety of scenery that Booth and the successive tenants of the theatre were known to have used during its thirteen year 13 history. Additional support for the successful operation of the machinery is offered by the fact that when the theatre finally met its end in 1883 the equipment was removed and installed at the newly refurbished Park 14 Theatre. It is not known how many theatres followed Booth’s lead in installing hydraulic machinery. Once the precedent 46 P /3 T O /V /Z O O R O L L E R . G tU IO B T ( F IX E D TO B M p O F C Y U N D G R .) L o w e r l / / v i / t s T o f > JT/H5F MANAGtGRJs CoN.TR.OL L C V E P STOP DOWM UP C O A /T R O L R O D A C T U A T O R . (F IX B P TO p/CTO.M R O D ) TRAVEL L/WHT/NG C O N TR O L R .O O U P P E R L./MIT STOP* S O P S / W A TER PRESSURE F&OM T A /s /NS /A I Ro o t structure DR/VR WHEEL INLET 1 I/ALISC I OUTLET T\ a m //E/OF’ i S f i / / CYL/NDEP P / S r o N DEHLS ORfVE WHEEL R E D U C TIO N G E H E s u p p o r t t i m b e r s p i s t o n s e p l . LEA/RAcsE & U C R E T P A C K E D P / s r o N R & O w s t o n DJPA/N f /g u /z g / £ coujecru&AL c/tosssecnoH q f a hyorjuuc x a m u seo a t b o o th's w t a t z s /aoi-zees had been established it ceased to be newsworthy and was no longer specifically noted in the accounts of most subse quent theatre openings. However, if any contemporary theatres had elected to install power operated stage equipment it most surely would have been hydraulically driven because at that time it was the only satisfactory method available. Steam power would not likely have been able to provide a smooth enough operation under the heavy, variable loading conditions, and electrical hoists and lifting devices did not come into general use until about 15 1890. Furthermore, hydraulic power was then coming into its own as a general power source and many firms were manu facturing industrial equipment that could be easily adapted to theatrical use. For instance, dockside cranes similar in construction to Booth's actuating rams were introduced 16 around 1860 and hydraulic elevators had been in use 17 since 1854. During the last quarter of the nineteenth century several European cities had even developed systems for the supply of industrial hydraulic power from central pumping stations. The city of London, for instance, had a municipal power system with five or six large pumping stations and over eighty-five miles of underground pressure mains which measured up to seven inches in diameter, and through the use of differential pumps and heavily weighted accumulators it provided the incredible working pressure 1 8 (for its time) of 750 psi. 48 Andrew Brown System A Scottish stage engineer named Andrew Brown obtained a patent in 1875 for an integrated hydraulic system in which the overhead rigging battens, a group of stage bridges and sinks, and an ingenious auditorium air circula tion device were all powered by a remotely located steam 19 driven hydraulic pump (Figure 17). The pump was used to charge a large accumulator which smoothed out the pressure pulsations from the pump and stored sufficient energy to handle multiple actuator operations. This arrangement also permitted a higher system operating pressure than would have been possible with the static head of water from a reservoir in the attic of the theatre. The higher operat ing pressure, in turn, allowed the use of smaller diameter actuators and feed lines. The rigging and lift actuators were of similar con struction, which consisted of a hydraulic cylinder with a block of sheaves attached to the piston rod and another at the head-end of the cylinder. The sheaves were then wrapped with cables and produced an arrangement like a block-and-tackle system in reverse, the batten cable being pulled a distance proportional to twice the number of rod sheaves times the distance that the rod moves away from the cylinder (Figure 18). The actuators were fitted with a set of threaded rods with adjustable nuts which acted to physi cally restrict the stroke of the piston rod and hold the 49 ^ i t ^ to I 1 ^ 1 i a§S| 'oQ^n. F/6UR£ t7 ANDREW BROWN SYSTEM - /NTEGZAreo s t / ig e poiajsr layout ( f S 7 s ) , — I £ k K Q c ^ [jj io«| luunmmiimnmnnunnnunnDnDPBBn jB0DP3^i c N^CO 00 s S 1 s 5 A>A/OP£~IA/ B&OW N S Y S TE M ~ P Y D RAUL IC ACTUATOR. W ITH A : / TRAVEL MULTIPLICATION BLOCKS net cable travel to predetermined limits. There were twelve power operated lines in the rigging system, one for the main curtain, one for the act drop, and ten for the scenic drops or "cloths." Presuming that the rigging actuators each had four rod sheaves and a total piston travel of around four feet, then the maximum batten travel of the rigging system would have been limited to 20 around thirty-two feet. This is substantiated by the positioning of a set of spring loaded batten guides which protruded from beneath the floor of the first fly gallery. This arrangement would have provided adequate batten travel to remove hangings from view of the audience, but might have created some difficulties in loading the batten. The spring loaded batten guides were tensioned by a set of cables which were attached to a pair of ratchet wheels in the fly loft. The stage floor was fitted with an arrangement of four bridges and six sinks, all of which were hydraulically operated. These units were raised and lowered by a system of cables and pulleys in essentially the same manner that the rigging system was operated. It was not specified whether or not these units were counter-weighted to reduce the tare load on the actuators. The rigging and lift actuators were controlled from a station with a long bank of lever operated valves. The bank consisted of a large cast iron tank, which apparently 52 served as a combined water reservoir and control lever housing (Figure 19). Each control lever was connected to two three-way valves, one which regulated the flow of fluid to and from its actuator head-end port and the other to and from the rod-end port. The auditorium air circulation system consisted of a series of large actuator driven oscillating panels that pumped air through the house ventilation ducts in a manner remotely akin to the action of a fireplace bellows. Unfortunately, little evidence of this system is available beyond the basic patent document. It is not known whether or not the system was ever manufactured or installed in one of the Scottish theatres, so it is not possible to assess its actual performance capabilities. However, close scrutiny of the various actuator, valve, and support structure elements revealed a surprisingly sophis ticated level of hydraulic and mechanical design for its age, which suggests that if it was put into operation it probably functioned very satisfactorily. Asphelia System In 1882 an Austrian civil engineer named Gewinner designed the Asphelia Safety System, in which large stage platforms could be lifted, lowered, or inclined with the use of remotely controlled hydraulic rams (Figures 20, 21, 21 22, and 23). The rams, which were located in the 53 CONTROL LEVER. COM0/NEC> CONTROL LEVER fJ O U S J N O / W A T E R RESERVO/P. 3 - W A Y V A L V E S ADJUSTABLE VALVE TRAVEL STOPS RESERl/O/R - RETURN PORT PRESSURE PORT ACTUATOR C Y L I N D E R PORT A C l G U A Z E / ? A (Y D /P E W & R O W M S Y S T E M — ACTUAt o r Coa/ t -Rol m e c h a n /SAA 54 FIGUfZE C J i Ol A S P H E U A STAGE - WITH HYDRAULIC F IG U R E 21 A S P H E LIfl STfl6 £ ~ HYD/ZAUUC U F T ae.£AN6E//IENT T 1 1 E ‘ A S P I IA L E I A ’ S Y S T E M : S t a g e . O r i g i n a l D e s ig n . F lO . 6 6 . L O N G IT U D IN A L S E C T IO N . F/G U /ZE 2 2 ftS P H E U A SYSTEM - Lom rruD /N flL s £ c r/o N g i S W M igsiigp* Mil. ‘ ,\ S l ’ I 1 A I. I I A ’ S\ ST1.M : St a<; f. ( 'liit’ .iN.M I n v I :■ ^ v Tk \n vi i:si N n i h > F !G U G £ 2 3 ASPHELIA SYSTEM - L A T E fc flL SECT/ON 58 substage area were also used to power the overhead rigging. Judging from the apparent diameter of the rams it is esti mated that the working pressure for the system was con siderably higher than that used by Booth, but probably nothing like that used in the European municipal power systems. Auditorium Theatre The most notable nineteenth century American theatre since Booth's to utilize power driven stage machinery is the Auditorium Theatre in Chicago. It is an elaborate 4,200 seat structure that first opened in 1889 and remains as one of the outstanding examples of nineteenth century American theatre architecture. It was rightly proclaimed as the most highly mechanized American theatre of the period, and for over thirty years it provided Chicago with many first rate operatic productions as well as playing host to most of the big circuses and theatrical spectacles 22 such as Ben Hur and Max Reinhardt's The Miracle. Even an 23 occasional political convention was held there. The theatre maintained a position of relative prominence until the late twenties when the new Chicago Civic Opera House was opened in a more fashionable part of town. After that it declined rapidly and finally fell into disuse in 1941, except for a short stint as a bowling alley and USO center during World War II. The theatre was spared from the inevitable wrecking ball only because its walls happened to 59 be an integral structural element of a surrounding eleven story office building that had been taken over shortly after the war as the campus for Roosevelt University. It was finally restored in the mid-sixties to its approximate original configuration and has since been operating as a non-profit civic theatre. In spite of its age the Auditorium is still said to be one of the most versatile and acoustically perfect operatic theatres in the country. The ornate proscenium can be opened to an area seventy-five feet in width by forty feet high for large spectacles, conventions, and operatic or symphonic performances or closed down by means of a five ton hydraulically driven "reducing curtain" to a more work able forty-seven by thirty-three foot opening for recitals and dramatic productions (Figure 24). The Auditorium can also be reduced in size to a 2,500 seat capacity by the use of curtains which close off the sides of the main balcony, and by a series of hinged steel panels which swing down from the ceiling to close off the entire peanut gallery. The scenic functions of the theatre are facilitated by a well designed counterweight rigging system that services the entire ninety-seven by sixty-two foot stage area and 24 has "room enough to hang scenery for seven operas." Most of the performance area of the stage floor is fitted with a series of hydraulically powered lift platforms patterned after those used in the Asphelia System, and as one 60 05 AUDITORIUM THEATRE - p r o s c e n iu m h n c h w it h r e d u c in g H U U m s n ju w / n c .r u C U R TH IN observer noted, some of them moved "up or down as much as eighteen feet [and were] probably used to form hills or valleys. Others [made] rocking motions to simulate the 25 actions of waves." The platforms are laid out in five rows, each spanning the forty-six foot width of the center-stage area in a manner reminiscent of Booth’s installation. The first unit is about five feet wide and is positioned about nine feet behind the curtain line. The remaining four platforms are arranged in a group that encompasses the up-stage area to within eight feet of the back wall (Figure 25). They are each about 9-1/2 feet wide and are supported by two two- foot diameter rams which are fitted into pedestal type cylinders rising from the foundation of the cellar, or low er substage area (Figure 26). These platforms can be lowered to the mezzanine, or upper substage storage area. The cellar and mezzanine each have a 7-1/2 foot head clear ance. Each of the four upstage lift platforms incorporate a smaller 8-3/4 by 16-1/2 foot bridge within the main platform structure. These inner platforms are each sup ported by a single two-foot diameter ram with its cylinder embedded into a pit below the lower substage floor, which allows them to drop down to the cellar 17-1/2 feet below the stage (Figure 27). In addition to the center lift sections the main lift platform also has long trap sections with doors that can drop a few inches and roll to the side 62 FIGURE 2S fiU O ! TORHJM THEATRE ~ M A IM FLO O R P L A N FIGURE 26 A U D IT O R IU M THEATRE— B e tD G E u r n f r o m m e z z a n in e ^9 cn AUDITORIUM THEATRE - bridge on small steel tracks built into the underside of the platform structure. The main lift platforms are attached to their rams by an arrangement which permits the structure to tilt toward one side or the other as the rams are indi- 26 vidually raised to different elevations. Each hydraulic ram is controlled by a separate operating lever that is located on the mezzanine to the stage-right side of the platforms (Figure 28). The two levers that operate each platform are mounted as a pair so that they can be worked more or less in unison, with a trained operator manually making minor corrections in the lever positioning to visu ally keep the platform moving in a horizontal plane or to create whatever slope may be desired. The maximum lift height for each ram is controlled by the simple expedient of a stout length of chain that is secured to the underside of the platform and anchored to the base of the ram pedes- 97 tal (Figure 29). The control valves which feed the lift rams are grouped in a bank along the right side of the cellar and are connected to their remotely positioned operating levers by a complex arrangement of mechanical linkages (Figure 30). During the restoration of the theatre the only part of the stage lift system that was reactivated was the center lift section nearest the back wall. It is now used primarily as a freight elevator. As in Booth’s Theatre, power for the hydraulic 66 % A H * l •' < • # • 1 * * O) SI FIGURE 28 AUDITORIUM THEATRE - B R .ID G B LIFT C O M T R .O L LLl/LFS F/ GU f c£ AUD/TO£JUM TH E/)m e- M AIAl B fiL tD G E L / F T " r tE D / h L S 68 AUDITORIUM THEATRE - b e / d o e u e t c o a / t e o l VA LU E S 69 machinery was originally provided by water that was stored in large tanks at the top of the structure. In this case it was at the top of the surrounding office building, about two hundred feet above the level of the rams, which is equivalent to an approximate working pressure of 95 psi. This pressure, when applied to the two foot diameter hy draulic rams, is capable of generating a lifting force of over thirty tons per platform through its entire stroke, less the weight of the rams and the platform structure. The water-tank power supply was abandoned during the theatre’s reconstruction and replaced by an electrically driven water pump feeding a large tank located near the control valve area of the cellar (Figure 31). In addition to the system of hydraulic platforms with their built-in bridges and traps, two hydraulically driven "Faust traps" are located about four feet behind the cur tain line and to the right and left of stage center. Each trap platform is about three feet in diameter and is sup ported by a six inch hydraulic ram that is mounted on a pedestal in the cellar (Figure 32). The control levers are located on the mezzanine adjacent to the respective plat- 29 forms (Figure 33). The final element in the theatre's array of power driven stage machinery is the system of five horizontal hydraulic rams which are used to raise and lower the reduc ing curtain, the fire curtain, the silk curtain, and two 70 ^ ar M F IG U R E AUDITORIUM THEATRE — m e w w a t e r p u m p a n d t a n /c ---------------------- 8 A S F M E N T a m AUDITORIUM TH EA TR E-f a u s t t f a ------------------ P F D / S T P L 72 stage-width paint frames located along the back wall of the 30 stage (Figure 34). The layout of the rams is very simi lar to that used by Booth twenty years earlier, except that the rack-and-gear method of multiplying the stroke length was replaced by an arrangement of compound sheaves similar to those in the Andrew Brown system, with one block of sheaves fixed to the end of the rod and the other to the head-end of the cylinder (Figure 35). All of the rams in this system are two feet in diameter, but because of the differences in weight and travel of the curtains and scenery being lifted, the stroke of the rams varies from six to eight feet and the number of sheaves varies from four to six. The operating levers for the curtains are located at stage level just behind the stage manager's position along the right side of the proscenium wall, and the paint frame levers are found near the back corner of the stage. The levers are connected to their control valves by means of cable-driven linkages (Figure 36). The Auditorium Theatre was renowned in its prime for its many lavish operatic productions and its dramatic specticals, most of which were made possible, or at least greatly facilitated by the use of its elaborate stage machinery. However, by modern standards the hydraulic equipment is very crude, being neither automatically regu lated nor mechanically stabilized, and requiring especially trained operators to keep it manually running straight and 74 4 //• 4 1 i < L m t A 75 p is to n ro d TRAVEL L IM IT C ontrol r o d m o i s t C P 3 L E R O D S U P P O R T t r u c r S M U T -O F F V P L V £ F / G U R £ 3 5 " T < = > Co n t r o l V/)LV£ PQ K O O S M E ~ 4 V £ £ C Y L IN P E R . P/STON R o d E FROM CONTROL i* ♦ LV £ \ r - CYLINDER / PO RT F ----- , _ © ) - V 1 / i \ . ' / / / / / / / / / / / / H EAP — ^ SHEAVES PRESSURE FEED L/A/E AUDITO&/UM THEATRE — HYDRAULIC /Z 4 M LAYOUT F /G U G E AUDITORIUM TH E A TR E - C u e m /M l / f t CO NTRO L l/NLVLT 77 smooth. But on the other hand, this archaic equipment has proved through generations of use to be remarkably durable, safe and trouble-free, and those pieces which are again in operation are considered to be as "serviceable as [in] any 31 operatic stage anywhere." Even those items that were not put back into service during the renovation were left idle, not so much because of the cost of reactivation, as because of the current economics of the theatre which precludes the present undertaking of the type of scenic extravaganzas for which they were designed. In general, the lift is reported to operate more smoothly and quietly than most of the new 32 electric ones, and once the operating techniques are mastered the systems require very little attention and practically no maintenance other than an occasional servic ing of the hydraulic seals and cleaning up the water leak age. Even the legendary leakage problems, which caused the lift platforms to drift to a lower level over a long period of time, were easily resolved by placing an appropriately sized timber under the offending platform for it to settle . 33 onto . By the turn of the century large scale electrical generating plants had been developed which could transmit power to remote locations cheaper and easier than either 34 steam or hydraulic systems. In addition, the rotational output of electric motors was proving to be a more suitable form of movement for many applications than the limited 78 linear translation of most types of hydraulic equipment then available. The greater portability of electric motors also made them more adaptable to installations in which the power unit had to be mounted on a moving structure. Con sequently, electrically powered machinery was rapidly sup planting steam and hydraulic equipment in many industrial and commercial applications. Hippodrome Theatre New York's Hippodrome Theatre (1905-1939) was an excellent example of the trend toward the use of electrical 35 power. The entire visible stage area of this mammouth palace of spectacles was lifted by hydraulic power, but within this huge full stage lift were seven large traps that were raised and lowered by electric motors through a cable-pulley lifting system (Figures 37 and 38). Also, the grid over the fifty by two hundred foot stage was fitted with four sets of curved steel tracks that supported six traveling electric cranes which lifted most of the scenery and carried it on and off stage. Sixty spot-line winding drums were mounted along the sides of the stage which probably were driven by electrical power. The hydraulic lift system in the Hippodrome was very advanced for its time, and incorporated most of the basic features found in modern systems. The entire stage area behind the forty by ninety-six foot proscenium opening 79 FIGURE 37 N E W Y O R K . HIPPODROME - a u d ito riu m A M D s ta g e v M.fc- * * r— r £ s: \ v, V • % \ ■ - i, - SIf m M e t iSarsfiM • » * ! i inn fluNtek~ ' C G U K T t S . ‘ /SIGHTS p $ V / * MEW FIGURE 33 YORK. HIPPO D R . OME ~ S T A G E A PM ON S E C T /OPS oo i —1 could be elevated as a unit to a height of eight feet above the stage level by four twelve inch hydraulic actuators. This huge stage platform, which weighed over 150 tons, was supported by four deep plate girders, with the hydraulic rams located at the four intersecting points. Most of the mass of the stage, however, was offset by a system of immense counterweights. The movement of the stage was guided by a number of vertical steel columns which were fixed to the underside of the stage platform and rode in steel channels embedded into the surrounding walls (Figure 39). The cables suspending the counterweights, which were located directly below the guide channels, passed over sheaves at the top of the channels and down to their attach points at the bottom of the platform columns. In order to keep the stage platform from tilting too far and binding in the lift guides it was necessary to pro vide a mechanism that would maintain uniform rates of travel for the four separate hydraulic actuators regardless of the overall lift speed of the platform. This was accom plished by an ingenious mechanical feedback system which automatically equalized the rate of flow in the rams (Figure 40). Each ram was linked to a separate shaft in a control box by means of a chain-driven sprocket so that the shaft rotated in direct proportion to the travel of its respective ram. These shafts were, in turn, connected together in pairs through differential gear mechanisms so Mi • I * , - • % r h fi ' ■ ' i Q & S f e e T mm l(jU R .£ 3 9 NEW Y O R K . HIPPODROME- v ie w b e n e a th s ta g e /- /< 2 U /Z £ ^ N £ W Y 0 / S / C H / f > / 3 OD#. QM £~ 84 that any uneven rate of travel at any of the rams would im mediately produce a correcting movement at an equalizing valve to bring its flow rate into line with the others. It is assumed, since the system was operational for thirty- four years, that the response of the system was fast enough to prevent the stage platform from binding and yet slow enough to avoid excessive oscillation, or overcorrecting of the flow rates in the various rams. The problem of platform drift was resolved by the use of mechanical locks which secured the stage at various fixed elevations. To accomplish this, each of the platform lift columns was provided with a series of slots which could be engaged by large steel dogs that slid horizontally from housings secured to the fixed guide channels. All of the dogs were linked together by means of countershafting that was geared to a rack on the upper side of each dog. The countershafting was connected to an electric motor which, when turned on, moved all of the dogs in unison to engage or disengage the platform columns. Besides the vast stage area behind the proscenium arch the Hippodrome also boasted an elliptical apron that extended some sixty feet into the auditorium and was large enough to contain two forty-two foot circus rings. Both of the circus rings and the surrounding area of the apron were mounted on separate hydraulic lift systems so that any com bination of apron and/or ring could be lowered fourteen feet into a steel and concrete tank which could then be 85 flooded for aquatic spectacles. The lifts for these plat forms were similar to those on the main stage. Water for the apron tank was provided by three centrifugal pumps with a combined capacity of 8,000 gallons per minute. These pumps also serviced a twelve inch perforated pipe mounted fourteen feet above the stage floor and running 180 feet along the back wall, and an eight inch perforated pipe mounted just inside the runway at the back of the apron. These were used to produce smashing stage-width cascade effects with an accompanying flowing river effect along the surface of the flooded pit. In all of the commentary about the spectacular history of the Hippodrome there has been very little note as to the functioning or malfunctioning of its stage machinery, which 36 presumably bodes well for its general serviceability. The Hippodrome was one of the last great spectacle theatres to be built in America. The rise of the motion picture industry and other social and artistic factors soon changed the character of popular entertainment and with it 37 the shape of the physical playhouse. Most of the popular theatres built between the wars were combination vaudeville-motion picture houses, which placed little emphasis on those types of scenic display that required extensive machinery. For instance, the Pantages Theatre in Hollywood opened in 1930 as a large scale combination house with a fully equipped stage plus complete motion picture 86 projection facilities, yet it was limited in its power driven equipage to a single water operated orchestra o o lift. The Fox Theatre in St. Louis, built in 1927 as the largest combination house in the country aside from New York's Radio City Music Hall, fared a little better. In addition to a water hydraulic orchestra lift it boasts a twelve by twenty-four foot stage lift that can drop down about twenty feet to the stage basement and be raised ten 39 feet above stage level. It also has a provision for hydraulically lowering the motion picture speaker horns from behind the screen to clear the stage for theatrical performances. War Memorial Opera House Some of the large operatic theatres that were built between the wars were as elaborately outfitted as their earlier counterparts. However, by this time electrical machinery had gained preference in this country over the then dated hydraulic technology. For example, the War Memorial Opera House in San Francisco (1932) features an exceptional array of stage bridges, traps, and powered rigging lines, most of which are driven by electro mechanical devices. The only significant hydraulic com ponent in the theatre, aside from the conventional main stage bridge lifts, is the drive mechanism for the grand master control levers on the huge stage lighting panel 87 (Figures 41 and 42). Hydraulic actuators were used in this application because they provided smooth, variable control over one of the largest and most unwieldy autotransformer dimmer boards in the world. They also reduced to a simple push button operation an exercise that otherwise taxes the strength of 40 up to nine men on a single dimming operation. Unfortun ately, the system in its original configureation was limited to a fading time range of three to ten seconds, which has since proved inadequate for subtle light cues, and thence has been disconnected. This limitation could be easily corrected with more up-to-date valving components and perhaps the inclusion of an accumulator in the circuit, but it would be a wasted expense for an archaic lighting system that is soon destined for extinction. In spite of its limited application, this piece of equipment represents a significant step in the evolution of hydraulic machinery in the theatre because it marks one of the first uses of oil as the power transmission medium. The change from water to an oil medium in hydraulic machin ery was made possible partly through technological improve ments in seal materials and configureations and in new techniques for making fine metal finishes, and partly through the development of recirculating systems which allow the exhaust oil from an actuator to be reused rather than flushed down the drain as in the water systems. Some 88 s i i V f k ( m f ' G U R E4_ _ S / t A / F / Z / I N C I S C O 0 P £ £ 4 " £ > E /) M D M A S T E E --------- 90 of the obvious benefits of the change were reduced friction, corrosion and electrolysis, and the near elimination of metal galling at sliding surfaces. The greatest benefit, however, came out of the concept of the integrated recircu lating system, which led to the development of longer life high pressure pumps and control components, and ultimately to the self-contained mobile units which have found such wide-spread applications in the construction and aerospace industries. The real maturation of fluid power technology occurred during the mid-century wars with the development of self-adjusting seals, improved materials, and more sophisticated control mechanisms. Unfortunately, most theatre equipment designers have not been exposed to much modern fluid power technology until recently, and consequently, most of the present installations of fluid powered equipment in American thea tres are limited to traditional stage lift mechanisms and simple special purpose actuating devices. The use of up- to-date actuator mechanisms with sophisticated control cir cuitry is now just in the formative stages, and the concept of mobile power units for on-stage applications has barely even been considered. It is to those few exceptions to the usual fare that the remainder of this study is directed. 91 Notes Blaine. The hydraulic ram was invented thirty years before Bramah's press came into service in 1802 (p. B), but railroad and dock type cranes were not in general use until about 1850 (p. 192). 2 Actually, the first use of hydraulics in the Ameri can theatre occurred in the Lafayette Theatre in New York (1825-1829). The enormous 100 by 120 foot stage was said to be constructed so that it could be transformed into a huge tank and filled with water for aquatic performances (T. Allston Brown, A History of the New York Stage [New York: Benjamin Blom, Inc., 1903], pp. 24-26). Although this does constitute an application of hydraulics it is not considered as an example fluid power technology. 3 0. B. Bunce, "Behind, Below, and Above the Scenes," Appleton's Journal of Literature, Science, and Art, 3, No. 61 (1870), 589. 4 Bunce, p. 590. 5 Bunce, p. 591. This is the first known use of stage braces, which were required to support the freestanding scenery. 6 Page from Benson Sherwood's "Stage Plans, Booth's Theatre," found in Gerald Honaker, "Edwin Booth, Producer-- A Study of Four Productions at Booth's Theatre," Diss. Indiana University 1969, p. 116. ^Bunce, p. 590. ^Bunce, p. 590. 9 Bunce, p. 590. The water for the rams was lifted to the reservoirs by a large steam engine in the basement, which also doubled as a power source for the scene con struction machinery in the shop and the theatre air condi tioning system. "^Fifty psi was about an average operating pressure for American hydraulic machinery in those days. ■^Allen Nevins and M. H. Thomas, eds., The Diary of 92 George Templeton Strong (New York: Macmillan Company, 1952), p. 242. 12 Lucia Gilbert Calhoun, ’’Edwin Booth," The Galaxie, January 1869, p. 86. 13 For a detailed account of the scenic requirements in four representative productions see Honaker. ^Brown, p. 144. 15 Kenneth Hudson, Industrial Archeology, An Introduc- tion (London: John Baker, Publishers Ltd., 1963), p. 45. The first electric dockside crane in London was installed in 1892. 16 Aubrey Wilson, London’s Industrial Heritage (New York: Augustus M. Kelley, Publishers, 1968), p. 14. ■^Blaine, pp. 207-38. Blaine, pp. 175-89. 1 9 British patent A.D. 1875, 16 October, No. 3593. 20 The patent drawings were not dimensioned, so the piston travel was scaled from an approximation of the gal lery guard railing height adjacent to the rigging cylinder. 21 "100 Jahre Stahl im Theaterbau," Stahlkonstrukionen im Theaterbau, pp. 3-4. 22 Jonathan Pugh, "Restoring the Auditorium," Talmanac (Chicago: Talman Federal Savings and Loan Association, 1 9 6 4 ) , p . 8 . ^Pugh, pp. 4-5. ^Pugh, pp. 4-5. 25 Pugh, pp. 4-5. 26 The center-most pivot pins are fixed and the outer ones are made to move laterally to accommodate the dimen sional differences as the platforms change their angle of slope. 27 This safety feature was added to the system follow ing an operatic performance in which an operator failed to shut off the control levers in time to keep the platform rams from being pushed out of their cylinders, with 93 predictable results. From a statement by Monty Fasnacht, the present house manager, who worked as a stage hand at the theatre in the late 1920s. Personal interview, July 1974. 29 These traps also were not put back into service dur ing the renovation and, although they are still mechanical ly sound, the question of their future activation is problematical in that an air conditioning duct has been installed directly under the trap doors. 30 Like the one bridge platform that is now in use, the three curtain drive mechanisms were returned to service by merely checking them for structural integrity, repacking the hydraulic seals, and replacing a few rusted water lines. The paint-frame lifts were not reactivated. 2^"Pugh, p. 26. 32Pugh, p. 8 . ^Fasnacht . 34 Blaine, p. 146. 35 ”The New York Hippodrome,” Scientific American, 92, No. 12 (1905), 139-142. 36 For a detailed history of the Hippodrome see Norman Clark, The Mighty Hippodrome (New York: A. S. Barnes and Company, 1968. 37 Nicholas Vardac, Stage to Screen (New York: Benja min Blom, 1949). Vardac traces the interrelationship between the motion picture medium and the live theatre and discusses many of the influences that affected theatre design in the first half of this century. 38 Terry Helgesen, ”The Hollywood Pantages," Theatre Historical Society Publication, A-l, 1973. 3 9 ° Personal interview with Dion Peluso, Theatre Mana ger, Fox Theatre, St. Louis, August 5, 1973. 40 Personal interview with Jack Philpot, stage elec trician, War Memorial Opera House, San Francisco, March 24, 1975. 94 CHAPTER III THEATRE LIFT SYSTEMS Lift systems, which make up the bulk of power operated machinery in the theatre, come in many sizes and shapes and are referred to by different names depending on their func tion and origin. Large rectangular lift systems that span with width of the stage are often referred to simply as "sections," "platforms," or "elevators" in this country and "kulessengassen" in the Germanic countries.^ Sections are usually used in groups for multi-level staging or 2 scene shifting purposes. "Bridges" or "slabs" are similar to kulessengasse except that they are generally smaller and are often incorporated within the larger structure of the sections or kulessengassen. They are often used during a performance to produce special effects such as the raising or lowering of apparitions or simulating wave motions. "Sinks," such as were used in Booth's Theatre, also span the stage but are much narrower than bridges and are usually located between bridges or sections. Because of their narrow width they are limited to the raising and lowering of two-dimensional scenery from substage storage areas; consequently, they have little use in modern theatres. The removable cover over the sink is called a 95 3 slider. "Sloats" (or"Slotes”) are similar to sinks in their function of raising long pieces of scenery from below to stage level, but they are wider and have been used for raising performers or three-dimensional scenic elements through stage traps. Their use is traced back at least to 1843 where they are mentioned in a list of standard equip- 4 ment at Drury Lane. They were originally manually oper ated with the assistance of counter weights and hand winches. Modern versions of the sloat are often hydrauli- cally or electrically powered and function basically as trap lifts or trap hoists. Sloats have also been known as 5 "boots." Lifts that span the stage like bridges but are divided into three or four independent units across the stage are frequently called "segments," and sometimes 6 "rostra" or "podia" in continental theatres. Lift Functions The lifting machinery that moves scenery, performers, and audience seating arrangements above or below the stage or auditorium level can be classified according to four general functions: (1) multi-level staging, (2) scene shifting, (3) special effects, and (4) adaptable theatre configurations.^ Multi-level staging Many theatrical events are best presented when some of the scenic or performance areas are at different elevations 96 from the normal stage level. Orchestral and choral per formances usually require a stair-step arrangement while much of the operatic repertory is conducive to the use of large three-dimensional pieces situated at different levels on stage. Most dramatic works are also made more interest ing when played in settings that are juxtaposed vertically as well as horizontally. These variations in stage eleva tion can be accomplished by constructing platforms or podia for each application, which requires a considerable expen diture of time, manpower, and materials, or by utilizing prefabricated scaffolding systems of collapsible risers, which may still require much effort and can create an addi tional storage problem. The labor, material and storage factors may not be acute in theatres that do not do a great variety of productions in a given period of time, as in long-run houses, or where the operating budgets are ade quate and labor is relatively cheap, as in some educational institutions, but in theatres where time and production g costs are important other options may be in order. An obvious alternative is to incorporate mechanized lifts into the stage floor which can quickly raise, lower, or tilt portions of the performance area to suit a variety of sce nic or staging requirements. Scene shifting One of the main functions of most theatre lift systems is to facilitate the movement of scenery on and off stage. 97 Some theatres are designed so that scenic units or whole sets can be moved into position from storage areas below stage level. However, this form of scenic movement suf fers from several significant drawbacks. First, the speed of most mechanized lift systems is relatively slow compared with other methods of moving scenery, therefore, shifts of this type are usually restricted to those that occur during acts or long scene breaks, or between shows. The storage of scenery beneath the stage may also be a problem, partic ularly when large set pieces or wagon units are used. The height of the scenic elements to be lifted is, of course, limited by the height of the substage storage area and by the loading clearance of the lift platforms and the dis tance of their travel. Also, movement of large pieces of scenery on or off of a lift at the substage level requires an unobstructed storage space adjacent to the lift well, which minimizes the possibility of using traps or other lifts in those areas, and requires a stage with a large, unsupported floor span next to the lift. Also, the use of large lifts for moving scenery from a substage area can create a safety problem because of the gaping hole that is left in the stage when the lift is down. Although these problems are significant, they have been successfully 9 resolved in several notable applications. Special effects Lift mechanisms are often used for the raising and 98 lowering of performers or scenic elements from the view of an audience. These spectacular appearance or vanishing effects must be approached with caution, however, particu larly when power operated machinery and live performers are involved because of the risks of getting sundry things caught in the moving parts of the machinery or of inadver tently driving a loaded platform up to stage level before the stage floor has been opened up to receive it. Adaptable theatre configurations Various forms of open or modular staging require a type of a theatre in which the spacial relationships between the performing area and the audience area can be adjusted to suit a wide range of staging requirements. To do this the seating arrangements and the playing area must often be altered as to size, shape, and location. Mechan ized lifts have effectively accomplished this function in several modular theatre installations by creating a floor area that can be elevated in sections to produce various audience-performing area combinations. Many proscenium theatres utilize the orchestra pit to produce a limited variation in the audience-performer relationship by either creating an extended apron when it is in the fully raised position, effectively moving the stage toward the audience area, or by providing seating space when it is at the audi torium level, thereby moving the audience closer to the proscenium line. It is often used as a multi-level staging 99 device in its in-between positions. Basic Hydraulic Lift Components Most modern hydraulic stage lift systems are made from standardized components that are commonly used in elevator or industrial applications. A typical system con sists of a wood-covered platform that is supported by two or three hydraulic jacks, or rams, which fit into caissons, or holes bored into the subgrade beneath the bottom of the pit. The platform attachments and column strength of the rams are usually sufficient to keep the platform from tilting in an up and down stage direction but it does not preclude the possibility of lateral, cross-stage tilting due to unsynchronized movement of the rams. A positive equalizing mechanism is therefore usually required to keep the rams always level with each other. A suitable power supply and control mechanism is also provided. Jacks A typical hydraulic stage jack consists of a plunger that is made from thick walled seamless pipe which is accurately turned and polished to a mirror finish (Figure 43). A heavy bulkhead is welded to the bottom of the pipe to form the head of the plunger. A retaining ring is welded to the outside of the pipe near the bulkhead to keep the plunger from leaving the cylinder barrel in the event that the control mechanism should fail to shut off in the 100 * d - \ \ v *c - o 7 ; . S o V « • »P Xj P A C K IN G G L A N D P AC KIN G A IR B L E E D P O R T B A B B IT-LIN ED BEAE/NGS o /l s u p p l y P o r t C A S IN G -M O O NT/P0 BRACKETS P IT C H A N N E L S P L U N G E R BULKHEAD A N D S T O P R /N G F /G U /R £ 4 3 TYPICAL H YD RADL/C STA G E JACK. Co u & t -& s y ED O l/E N e. C O P o /Z fiT fO N 101 lift direction. In some designs the clearance between the outer surface of the ring and the wall of the cylinder is made just wide enough so that the actuating fluid can pass to or from the head-end of the ram without impeding the normal rate of travel and yet narrow enough so that it can act as a flow restrictor, keeping the platform from falling too fast in the event of a pump or valve failure or break in the fluid line. The outer cylinder or casing is usually made of heavy seamless steel pipe with a bulkhead welded to the lower end and often an additional inner bulkhead to absorb the impact from any inadvertent bottoming of the ram. The upper end of the casing is fitted with brackets for mounting the unit on pit channels, and a flange at the top which mates with the guide bearing and packing gland assemblies. A pair of babbet-lined steel guide bearings are usually fitted at the upper end of the cylinder to take the bulk of the side loading from the platform. The bear ing spacing must be sufficient to keep the coupling forces within acceptable limits when the ram is in the fully extended position. If the lift unit is adequately braced at the platform guides only one bearing may be required inside the jack. The oil inlet port is generally located just below the lower bearing and an air bleed valve is found near the upper-most oil cavity, which is usually just below the packing gland. A steel or malliable iron packing gland is fitted into the top of the cylinder to retain the 102 hydraulic seals, which most often are of the chevron, hollow-core flax, or molded synthetic slipper-seal designs, depending on the application."^ Stabilizer mechanisms Most stage lift systems in this country are equipped with a cable type equalizing mechanism (Figure 44) that works in principle like the parallel rule used on many drafting boards. It consists of a set of cable sheaves which are mounted within a pair of spreader channels that are attached to the top of the pit channels, just inboard of each ram. A vertical strut is attached to the underside of the platform next to the attach point of each ram, directly over the sheaves. These struts run in housings which are attached to platen plates on each jack cylinder and are embeded in a well along side of the cylinder. A cable, which is secured to the upper end of a strut, is stretched down and under its adjacent sheave, across to the other sheave, then over and down to another attach point at the bottom of the other strut. Another cable is stretched in a like manner from the opposite strut. These cables, which are held taut by tensioning screws, keep the platform from tilting excessively in the plane of the jacks irrespective of the load distribution. This is the most common type of stabilizing mechanism for multi-jack stage platforms. It is relatively straightforward, inexpensive 103 STAB/LtZ-ER. c a b l e a d j u s t in g s c r e w S T A B IL IZ E D C A B L E S T A B IL IZ E D S T D U T B E t/E L E D T O E G UARD -d l a t e o d m \— U* \ U /J E r T*1' * j 4 . JACK. C ASING S T A B IL IZ E D C A B L E S N E A I/E S r / G c t / z e S T D U T H O U S I N G B A S IC H Y D R A U L IC S T A G E U F T ( IN IT A C A B LE s t a b i l i z i n g /m e c h a n is m ) COOgTEISY DoyED CO/S.RO/Z./9T! OAJ 104 and effective, and requires only an occasional servicing to lubricate the sheaves and cables and check their tension. Small deviations from the horizontal alignment of the plat form are possible, however, if one cable should become excessively stretched. For this reason the cables must be provided in matched pairs so that they will both have the same elasticity. Even then, a slight tilting may occur during conditions of heavily unbalanced loading. Another method for stabilizing the platform that is used in hydraulic lifts, particularly in European theatres, is a torsion-shaft, rack-and-pinion arrangement wherein a vertical rack is secured to the platform frame next to each ram and rides up and down in a housing in a manner similar 12 to the cable stabilizer system (Figure 45). A torsion shaft is mounted in bearings along the pit channels and a pinion gear at each end engages with the respective racks. An unequal movement of the rams is resisted by the torsion al stiffness of the shaft which is in constant mesh with the racks. This arrangement is considerably more effective than the cable system but the cost is substantially greater. Power supplies The power supplies that drive most theatre lift sys tems are standardized self-contained units similar to those 13 used in elevator and industrial lift applications. The 105 TO/ZS/OAJ rt> B £ ¥ CD o $ k) S I ft ISAC/C A N D Ge/ l / s Sr/lB/LIZE/i M £ C //A W S M smallest size range covers lift requirements up to about five horsepower. The pumping unit is usually a positive displacement gear or vane type with a working pressure of about 200 psi and is generally mounted on a reservoir of about fifty gallon capacity. The basic valving consists of a relief valve, a check valve, and an actuating valve. An oil strainer and electrical and pressure overload pro visions are also included. The next general size range covers applications with about a five to ten horsepower load requirement. These units mostly use gear pumps which are installed under the reservoir to ensure positive pump priming and to eliminate cavitation. For applications above the ten horsepower range high volume positive dis placement pumps are used to handle the increased flow requirements. The pumping requirements for a lift system are dependent upon the greatest total load that must be lifted, including the weight of the ram and the platform structure, and upon its maximum rate of travel. The load capacity of the individual ram is usually determined by changing the ram size with a consequent change in the flow demand, rather than by varying the operating pressure, which is normally held in the 200 to 500 psi range. Control features The control mechanism for most conventional orchestra lift systems consists of a panel with MupM and "down" buttons that require a constant pressure to maintain 107 movement. Passenger elevator type control systems that automatically dispatch a lift to a predetermined location with the touch of a button are not normally used except in the larger, more complex systems because of the potential safety hazard. In this respect the control panels are almost always within sight of the upper side of the lift platform so that the operator can watch for clearance problems. The problem of safety in a powered stage lift is always greater than for an elevator in which the passengers or cargo ride in an enclosed car. Most stage lifts, of necessity, have exposed platforms with no safety barrier around the edges; although the underside can usually be fitted with a protective skirt that acts as a visual mask ing and keeps people and objects from getting caught under neath when the platform is lowered from above stage level. However, the underside of the stage floor is generally exposed on the sides that are open to the substage level when the lift is in its lowered position. Consequently, they require some means of preventing squashed appendages such as beveled toe guards or an automatic stop mechanism similar in function to the retractable safety edges on passenger elevator doors. The risk of falling into a chasm in a blackout remains a hazard of the theatre. 108 Stage Lift Systems Orchestra lifts The most common type of stage lift system is the orchestra pit lift. Most proscenium type theatres have an orchestra pit that is situated between the stage and the auditorium, and often extends into a cavern beneath the stage (Figure 46A). In theatres where dramatic works are generally performed the pit may be about six to twelve feet across with the substage recess, if any, usually limited to about six to ten feet under the front edge of the stage so as not to interfere with on-stage lifts or traps. Since the gap created by an empty orchestra pit is usually detrimental to the actor-audience relationship in dramatic productions, it is commonly filled in to either produce a forestage or to provide additional seating (Figures 46B and 46C). This is often done manually by constructing wooden platforms on a system of tressels or by utilizing some form of prefabricated scaffolding. A more desirable solution is to install a mechanized lift system into the pit. Orchestra lifts are occasionally divided into two or three segments across the stage and sometimes even into two lateral segments, one upstage of the other, so that a combination of staging and orchestra arrangements are possible. Golden West College. The hydraulic lift at Golden West College in Huntington Beach, California is fairly 109 A - Ao ^p t p d p o p o/£. c h£s t/3/> i/S£ 3 - ADflPTPO POP PDDPO POPPSTflGP d C - AD A PTED P O P fl£>£>£0 S£rtTM <5 F / G U & £ 4 6 A P P P P A 3 Z P 3 P C p £ T S T 3 A P /p I//P P /A T /Q A Z S representative of a conventional type of orchestra lift system found in many dramatic theatres (Figure 47). Its primary function is as an adaptable theatre device for dropping the single lift platform to the level of a recessed orchestra alcove, raising it to auditorium level for additional seating, or to stage level to provide an additional playing area. It can also be used to some extent as a multi-staging device by placing scenery or part of the action on it with it stopped at an intermediate position. In addition, it has limited capabilities in scene shifting and for creating such special effects as raising the orchestra or scenic elements into view during a performance, but its slow speed limits this possibility to special occasions. Apart from its theatrical perfor mance functions the lift is used extensively as a freight elevator for moving supplies and stage equipment to sub stage storage areas. The lift system has a self-contained power supply located in an isolated substage area (Figure 48) and a control station on the back side of the stage- right proscenium wall, next to the stage manager's posi tion. The installation has proved to be nearly trouble free and has required minimal maintenance during its five years of service. It has also exhibited negligible leakage characteristics, and has never shown any tendency to drift 14 downwards over long periods of inoperation. Ill FIGURE 4-7 GOLDEN W EST COLLEGE- H Y D Z .4 U L /C 0ZC H E 5TK / } ----------------------------------- l /f t w c --------------- 113 Walnut Street Theatre. Occasionally it becomes neces sary to install an orchestra lift into a pit which does not have enough depth for the caissons that are required by a conventional hydraulic jack system. One solution to the problem is to use a system of telescoping hydraulic cylin ders similar in concept to that installed at the Walnut Street Theatre in Philadelphia (Figure 49). This theatre was built in 1809 and has been in continuous use since then except for two or three short closings for modernization. The latest remodeling was done in 1967-68 and included the addition of an orchestra lift within the general structure of the existing pit. This system is divided into three lift segments, each of which is supported by a single telescoping jack that has a compressed length of approxi mately one-third of its extended length. These jacks per mitted an installation with little or no excavation below the bottom level of the existing pit. However, since telescoping cylinders are characterized by a relatively low level of lateral stability, the attached platforms require a substantial guide system to keep them running straight and level. Regrettably, the only stabilizing mechanism that was provided was a set of guide tracks along the front wall of the pit, in which ride small nylon shoes that are attached to the underside of the platform. This has proved totally unsatisfactory in that the shoes tend to hang-up in the guide channels during the lift operation and the 114 115 . — , 7— , FIGURE 45 w a l n u t s t r e e t t h e a t r e - o r c h e s t r a l i f t s y s te m platforms require considerable manual persuasion with hammers and crow bars to keep them running straight. In addition, the system requires a set of legs to be placed under each platform to keep it level and fixed at the 15 desired operating height. Many of the problems could have been alleviated by using a more substantial arrangement of guide tracks and platform rollers or guide shoes to provide better support against horizontal movement as well as to control some of the inevitable tilting to be expected from a platform supported by a single telescoping cylinder. The excessive tilting and consequent platform binding caused by the lateral instability of the platform balanced on the single rams could have been alleviated by one of several possible lift stabilizing methods that do not require the excavation of deep holes beneath the pit. One method that could be employed would be to use a torsion bar, rack-and-pinion arrangement similar to the conventional stabilizing method except that the racks would be fixed to the pit walls and the pinion shaft attached to the moving platforms. In this application stability in both directions could be obtained by mounting a pair of countershafts diagonally across the undercarriage of the platform with the gears at the ends of both shafts engaging with racks anchored vertically to the pit walls at each corner of the platform. However, the cost might be 116 prohibitive for this application. A system of sprockets and vertically secured roller chains could also be used, which would be much cheaper than a rack-and-pinion configuration, but would also introduce a greater amount of back-lash into the system. In either case a rigid structure would be required at each corner of the lifts for attaching the racks or chains, which might also prove unsatisfactory in this particular application. Another method would be to employ a stabilizing cable arrangement wherein the lower end of the cable does not descend into a hole in the pit as in most conventional systems but traverses to the opposite end of the pit, passes under a sheave, travels back down to an attachment on the underside of the platform (Figure 50). This method also has the limitation of requiring attach points near stage level at each corner of each platform. San Diego State University. A more effective solution to the problem of installing a lift in a shallow orchestra pit would be to utilize a scissors type system similar to the one which has been in service at San Diego State Uni versity since 1967 (Figure 51). This theatre has a curved orchestra pit about 7 1/2 feet across by 27 feet wide by 10 feet deep. In addition, it has an adjacent ten foot recess under the lip of the stage to accommodate a reasonably large school orchestra for their annual musical productions. 117 U P P E E S T A 3 /L /Z E E . S B E A l/E S ATTACHED TO P /T WALL , STABIL/ZEP CABLE ADJ UST/ ED SCeew E L A T E D E M TELESCO P/C JACZ G T A B /L /E E E C A B L E -L D W E P S T A B /L /Z E P S E E P t/E S A E A C H ED T O E P A A TE O B E /T E L . OOP. F /G L /G B S 'O S B A L L O W E '/T C A B L E S T A 3 /L ./Z /A /6 ATECAAAJ/ SAA 118 119 FIGUR.E SI S/M/ DIE6D S T A T E U N I V E R . S I T Y ~ The basic lift mechanism was purchased as a standard four foot by twenty foot unit from a manufacturer of industrial 16 hydraulic lifts. It consists of two four foot by ten foot scissorrs lift units which are attached to a common base and connected at the center link pins by a pair of stabilizer bars to keep the platform level regardless of its load distribution. The two actuators are driven by a small built-in power supply mounted in the center of the base (Figure 52). The curved orchestra platform was added to the basic lift unit by the contractor who installed the 17 equipment. The system has a 15,000 pound static load capacity and can be raised a total of 7 feet, from a recessed orchestra position to an elevation 9 inches above the stage, which mates with the height of their standard wagon and riser units. When the platform is at stage level, which is its most frequent operating height, a set of four stanchions are swung down from a stowed position under the platform to provide support against jack slippage. At any other eleva tion the platform is supported by the jacks only and, as is reported, there is little or no downward drift during the run of a show. The horizontal stability and resistance to lateral movement in the link pivoting plane (across the stage) is very good, but some lateral bracing may be required to prevent a slight movement in the axial direc tion of the link pivots (up-and-down stage), particularly 120 121 S/)N DIE6Q STATE. UNIVERSITY- L IF T PO W ER SUPPL Y when the platform is positioned above stage level. The unit was not designed for, nor intended to be used as a passenger lift, and it has no automatic shut-off devices or other safety mechanisms except for a beveled sheet-metal toe guard around its perimeter. This cost-saving measure was made possible by the use of two actuating switches in series, one at stage level and one in the pit, so that two operators are required, each visually monitoring their area of the lift operation. 18 This system is very basic, inexpensive, easy and quick to operate, and is easily and economically maintained. The most serious complaint lodged by its users is that the concrete wall on the auditorium side of the pit is not quite vertical and the platform tends to scrape against it on the way up or down. In general, within the limits that were set for it, the users are very satisfied with their 19 budget-minded lift system. Main-stage lifts Most main-stage lifts are very similar to their orchestra lift counterparts except that they vary in size from small portable trap lifts to immense platforms that cover nearly the entire stage area. Very large lifts tend to be relatively impractical, however, because of the time that is required for making scene shifts and the gaping hole that is left when the lift is down, along with the restrictions of being able to 122 create multi-level effects only by the raising or lowering of the entire playing area. University of Utah. The University of Utah at Salt Lake City provides an example of a large single platform hydraulic lift system whose function is occasionally hindered by its great size. The huge lift platform covers most of the playing area of the stage and sinks about thirty feet to a scene storage area in the cellar. It is reported that scene shifts with this lift system are so time consuming that its use is generally limited to spec tacular events, for creating simple multi-level staging arrangements, or as a freight elevator.^ The creation of spectacular effects, such as full scale settings sinking into the sunset, is the major forte of large single lift units; but this type of scenic effect has its greatest impact when it is used very sparingly. It is difficult to justify such a system as a general piece of stage equipment except in theatres that are specifically designed for the production of large scale spectacles, or perhaps as a very opulent educational device. Hofburg Theatre. An effective solution to the problem of filling the hole left in a stage floor as a large single lift or group of bridges coupled together are sunk below stage level is to employ a large wagon or platform that can roll on from the back or side of the stage and span the 123 gap. The Hofburg Theatre in Vienna had such an arrangement as early as 1888. This theatre boasted a series of seven hydraulically operated bridges about eight feet across by thirty-eight feet wide that could be operated independently or coupled together in any combination. The whole of the seven ’’bridges," if sunk together, would form a well measuring 57 feet (17.30 meters) in depth, 38 feet (11.60 meters) in width, and sunk nearly 14 feet (4.25 meters) below stage floor l e v e l . 2 1 At the back of the stage, on tracks, was a ’’rolling way” or ’’slab” about twenty-four feet across and forty feet wide on which scenes were moved bodily from front to back of the stage, or vice versa. This ’’rolling way” was at stage floor level, and reached over the independent lift bridges when they were sunk, to make way for this covering. Thus any three of the seven bridges could be covered at any one time. In addition, a set of traps were located in the "rolling way” which corresponded with the traps in the bridges so that performers or scenic elements could be brought up from below with the lift already at stage level and the "slab” covering it. MGM Grand Hotel. A modern version of the same staging principle can be found at the MGM Grand Hotel in Las Vegas. This installation has a large hydraulically operated lift that is used to raise various settings including a gigantic aquarium with live porpoises. After the lift has descended 124 with its load a section of the stage adjacent to the lift can be moved over it to cover the cavity.^ The high initial cost of power operated "under machinery" in a theatre can only be justified when it is put to frequent use or when the desired theatrical effects cannot be produced in any other way, such as at the MGM Grand Hotel. In theatres with a varied production schedule and extensive scenic demands a lift system should be flex ible enough to accomplish a wide variety of functions. This type of flexibility is best achieved by dividing the lift system into as many segments as possible, consistent with the performance requirements and operating budget of the producing facility. Large operatic houses are general ly the only type of theatre that can economically justify the expense of a system of full-stage sectional bridges. Hesse State Theatre. This type of installation is commonly found in the theatres of Central Europe, particu larly in Germany and Austria, where they have long been blessed with large government subsidies, a vast repertory that is rotated each performance, and great popular sup port. The Hesse State Theatre in Wisebaden, German for instance, has had a combination electro-hydraulic lift system of six large sectional lifts which have been in regular use since the early 1900s. Each section is counterweighted and driven from the mezzanine to stage 125 level by an electric motor. Within each section is a smaller bridge, about thirty-six feet wide by four feet across that is operated by a hydraulic ram. These units move with the larger sections at the substage levels, but are also capable of extending several feet above the stage. The theatre is now undergoing its first major renovation since it was built, and the only significant revision that is planned for the lift installation is to replace the original electric drive motors and update the control systems. The basic hydraulic lift arrangement is expected to remain unaltered.^ War Memorial Opera House. A number of American opera tic theatres also utilize various types of sectional lift systems. The War Memorial Opera House in San Francisco has a system of four forty-nine by four foot bridges spanning the playing area of the stage and a narrow forty-nine by two foot bridge or "scroto" at the curtain line, plus an 24 electric orchestra lift system in three segments. Metropolitan Opera House. The most extensive use of stage lifts in American theatres is at the Metropolitan Opera House. The stage of this theatre is divided into seven sectional lifts, each sixty feet in width by eight feet across, with a smaller section at the front used as an equalizer flap (Figure 53). Most of the lifts have a load capacity of about 20,000 pounds, which can be carried 126 o/zchf^sr/s./} i /p t / Qizcf-/e s t & a u /= r ^ £GU/!UZ.£/Z. ELAf=> I S T A G E l / f t / S T A G E L / F T 2. STAG E L /F T 3 S T A G E L /F T A STA G E L /F T 5 S T A G E L /P T G S T A G E L /F T 7 F / G U / Z E S 3 L / F r T P L A N - M E T P O P O L /T A N O P E P A H O U S E through nearly thirty feet of travel at lift rates ranging from thirteen to forty feet per minute. In addition to the stage lifts there are two orchestra lifts, divided laterally. The main orchestra lift can raise a 48,500 pound load at a rate of ten feet per minute and support a static load of over 120,000 pounds with the unit locked in a fixed position. Each section of the stage lift system is supported by two large hydraulic rams and is kept level by a set of conventional stabilizing cables (Figure 54). They are restrained in their horizontal movement by a set of guides which ride in vertical steel columns at the ends of the platform. The guide structures are perforated from top to bottom by a series of rectangular hoses on six inch centers (Figure 55). These holes are for a mechanical locking device that prevents the stage platform from drifting down over long periods of time due to random leakage of the valves or actuators. After the unit has been moved to its selected position a separate hydraulic actuator mechanism pushes large steel locking bars into their respective holes, which keeps the platform fixed at that level (Figure 56). A special control panel (Figure 57) monitors the platform position and sequentially ener gizes the lift and locking pin control valves to raise the platform slightly in order to relieve the weight of the lift assembly from the lock pins, then remove the pins from their respective slots, move the platform to its new 128 < • DO CD FIGUR.E 54 METROPOLITAN OPERA H0U3E - &R.IDGE L /F T SECTIONS H 1 130 131 METROPOLITAN OPERA HOUSE F/6UKE M E T /S O P O L /r/JA / 0 f > £ £ A H O U S E - m o m i td k i n g £- 132 25 position, and re-engage the pins into the adjacent slots. This lock pin arrangement has proved to be an effec tive anti-drift system for this particular installation. It is a relatively complicated and costly arrangement, however, and was not implemented without its share of developmental problems. The main difficulty encountered in this, and with a number of other sliding lock pin con figurations, is that if, for some reason, the lift assembly should become misaligned with the guide structure, or the lock pin control system should malfunction so that the lock pins would not retract before the lift rams are pres surized, then the pins would inevitably be sheared by the immense force of the rams, or worse, bend enough to jam the platform at some intermediate position. Another type of anti-drift locking device that has been successfully employed in sectional lift systems is exemplified by the one used at the Weisbaden Theatre. In this case the platform is retained by means of a simple ratchet mechanism consisting of an arm on the platform that is manually pulled away from a row of engagement teeth in an adjacent support column when the platform has been lifted slightly. The platform is then moved up or down to its desired level where the arm is allowed to re-engage by the force of gravity. In this installation, however, the platform is counterbalanced and the forces on the locking arm are much less than in one supported solely by a set of 133 hydraulic rams. There is also a possibility of malfunction with this type of system if the manually or gravity oper ated levers do not fully engage with their ratchet teeth, although this apparently has never caused any difficulty 26 at Weisbaden. Another solution to the drift problem would be to employ a system of automatic releveling valves similar to those employed in many commercial elevator systems. They could be actuated by a limit-switch mechanism so that when, or if, the platform falls a fraction of an inch below a nominal preset position, a small amount of additional fluid would be pumped into the lift ram to bring it back up. This arrangement could also be used in conjunction with an accumulator or a separate small pumping device to save the main pumping system from being engaged to supply such a small flow demand. The main drawback with this approach, however, is that the addition of more valves and hydraulic components also invites the possibility of additional leak age and operational malfunctions, and it does not provide any means of positive restraint in the event of a major failure in the hydraulic system, however remote that pos sibility may be. Adaptable and modular theatre lifts The use of fluid power as a tool of modern stage tech nology has been effectively put to service in recent years 134 in the development of adaptable and modular theatres. "Adaptable” or "multiform" theatres are generally con sidered to include those facilities wherein one basic theatre form, such as proscenium staging, can be quickly converted to another form, such as end, thrust, or trans verse staging. "Modular" theatres are usually thought of as a large room or "uncommitted space" in which the audi ence and performance areas can be arranged in a wide vari- 27 ety of combinations. Vivian Beaumont Theatre. The Vivian Beaumont Theatre in Lincoln Center is an example of an adaptable theatre that can be converted from a proscenium to a thrust con figuration with the use of a hydraulically operated lift system. This 1,140 seat theatre was designed with a wide angled amphitheatre seating arrangement which faces a more- or-less conventional proscenium type stage with an opening that can be adjusted from a maximum of fifty-six feet wide and thirty-five feet high for proscenium productions to a minimum of nine feet wide by six feet high for thrust usage. The stage has a shallow apron in front of which is a single hydraulic lift platform approximately twenty-two feet wide by fifteen feet deep. When the theatre is in the proscenium configuration the lift is at auditorium level and is fitted with several rows of seats on a moveable structure. When the theatre is to be converted to a thrust configuration the lift platform is lowered to a basement 135 level where the seats are rolled off and replaced by a thrust stage segment which is then raised up to stage level (Figure 58).^ Loeb Drama Center. The Loeb Drama Center near Harvard University similarly employs a hydraulic lift system that can raise or lower platforms for use as a stage or for audience seating (Figure 59). In this case, however, the moveable seating is mounted on two rolling segments that can either rest on the lift platforms when they are at auditorium level to produce a proscenium type of staging or be manually moved around to the sides of the auditorium when the lift platforms are elevated to form the thrust part of the stage. The moveable seating can also be rolled clear around to the back of the stage and pointed toward the auditorium proper to form a transverse staging con- 29 figuration . California State University at Long Beach. The Studio Theatre at California State University at Long Beach offers another combination of staging configurations that can be achieved through the use of power driven lift platforms. This facility is designed to be easily adapted to arena, deep thrust or proscenium arrangements, with some varia tions in between (Figure 60). The structure is made with three or four permanently stepped seating levels extending around three sides of the auditorium. The fourth side 136 J I F R O S C E N /U M T H R U S T C O N F IG U R A T IO N C O N F IG U R A T IO N H YD R .A U L/C L /F T E/GU/ZE S3 V IV IA N B E A U M O N T T H E A T R E - /ADAPTABLE S TA G E 137 STAGE A PR OH OR. p/r (C/PP4-) F F O S C E A /W M S T A G E C O A /F /G U F A T /O N T H R U S T STAGE CONE/OUT FT/ON i ; : r « ( l i f t 4) l i / I \ S T A G E I \ Ll^ ) \ ( l i f t s ) {(t-F ri) T R ftN Q V E R S E S TA G E C O N F IG U R A T IO N F / G U / Z S S 9 LOEB D /eA /M CENTER - STAGE COMBWAT/ONS 138 & 4C K sr/R G B \ — c u /z t/ j/ a/ l / a j b 3 Af=>/€OAJ S C /S 3 0 /Z S /L //^ r SBCT/OAJS x 7 T ///Z u s r S C /S 5 0 & S L //^ T S^CT/OAJS fr&c>iA/s £>/=■ s/&£/tA/c> s ^ r ^ r s ^ . ~ B / G U / Z B G O CAL/P'O^AZ/A STAT£ l/A f/]/k& S >lTY g r L0MO BE'/ICH — A D A P T A B L E : T A E A T A . E S T /96 E E =L/ ?aJ 139 contains a curtained proscenium arch with a small stage house behind it. The area in the center is divided into seven sections on hydraulic lifts, each four feet across and varying in width from twenty feet at the auditorium side to the full proscenium width of thirty-five feet under the arch. Each of the lift sections consists of a single plat form that can be raised to a height of at least six feet by a series of hydraulic scissors jacks (Figure 61). The five down-stage sections are each supported by two jacks. The extreme up-stage section (under the proscenium) uses four. A simple mechanical lock pin device is incorporated to hold the platform, on five inch increments, against slippage or inadvertent actuation. The use of scissors jacks that fold to a collapsed height of twelve inches kept the recess under the lifts to a minimum, and by using commercial hydraulic units the design was simplified and the costs were kept to a minimum. The control panel for the system is located at one corner of the auditorium and consists of a series of key-turned switches to move the hoists either up or down depending upon which way the key is turned in the switch. Like the San Diego scissors installation this system was not designed nor intended to be used for moving scenery or performers during a production. When the platforms under the proscenium arch are at stage level and the center platforms are in a lowered 140 FIGURE 6>t ~ CALIFORNIA STATE UNIVERSITY £T LON6 BEACH- SCISSO RS L IF T SECTIONS position with seats installed the facility functions as a more-or-less conventional proscenium type theatre. To aid in this function the seats along the sides of the house are on swivels so that they can be physically pivoted in the direction of the stage for better viewing. The pro scenium configuration can easily be modified to form vari ous degrees of thrust staging simply by removing the seats from the front rows of the centerstage area and raising the respective lift platforms to a suitable staging level. With all of the center seating area converted into a stage platform the facility becomes a 200 seat deep-thrust stage theatre with full scenic capabilities behind the proscenium. It can also be converted into an arena, or "theatre-in-the- square" configuration by drawing the proscenium curtain and placing seats on the lift sections under the arch with them positioned at levels corresponding to the steps of the seating on the other three sides. Although this theatre offers considerably more flexi bility than most adaptable theatres, it could not be con sidered as a totally flexible facility because of the fixed seating levels on three sides of the house. But if more flexibility than already exists is desired, even those seats can be removed. During the three years that this theatre has been in operation no major problems have been reported in the use of any of the lift mechanisms. However, none of the 142 platforms, with their independently powered jacks, have yet been subjected to a lift operation while supporting a heavily unbalanced load. If a unit should fail to operate under such conditions the separate scissors mechanisms could always be interconnected with a mechanical linkage and then driven by a single actuator. Although the system can be operated by one man at the switch panel, the ser vices of an assistant are usually enlisted to pull a pin in the floor of each platform which releases the locking device. None of the lock pin mechanisms has thus far mal functioned and on one or more occasions the system has been used in productions with the platforms at intermediate levels, where the lock pins do not function, with no noticeable downdrift during the run of the show. In general, this installation is proving to be nearly as flexible as some modular theatres, but with less com plexity and fewer man-power requirements. It has been reported that the whole theatre arrangement can be con verted from one type of staging to another in less than one „, 30 afternoon. The wide variety of staging configurations that have been used in this theatre to date have adequately demon strated its versatility; however, it has not achieved this status without substantial compromises in its theatrical effectiveness and the resultant limitations on audience reception. For example, when the theatre is in the full 143 proscenium configuration the usable staging area is severe ly restricted because of the extremely wide sight lines from the few seats that extend along the sides of the house near the proscenium wall. The sight lines among the seats on the recessed lift platforms in front of the stage also impose a problem of inadequacy in the proscenium or mild thrust modes. Likewise, when the facility is in the full thrust configuration the staging area is so deep that the designers have had difficulty in effectively filling the visual space, and many performers have been overly taxed in utilizing the stretched-out playing area. Also, the audience along the sides of the thrust are subjected to the Mping-pongM syndrome of having to alternately watch the action at the proscenium end and then at the thrust end. The swiveling seats along the sides of the house also tend to be self-defeating in some modes of use. They are very effective in allowing the audience to face toward the stage when the theatre is in the proscenium configura tion, but their swiveling action necessitates an audience spacing of over twenty-eight inches per seat, which severe ly hampers the sense of intimacy that is vital to the whole concept of open staging. This very wide seat spacing has been partially defended on the grounds that the resulting 175 seat full thrust seating capacity assures a full house for many of their major productions; but by the same token, the guarantee of a limited, captive audience also tends to 144 negate the traditional performance incentive of having to prove oneself at the box office. By and large this theatre, like most things that have been designed for a multiplicity of purposes, cannot accomplish any of them as well as one that has been de signed for a single purpose. But within the limits that were set for it, it seems to be serving its purpose as a flexible educational theatre facility better than many other "adaptable" arrangements. The development of the "modular” theatre concept of staging evolved from the Appian ideal of a performance space where actor and audience could communicate with the least possible physical limitations: that is, a simple building "merely to cover this space where we work— no 31 stage, no amphitheatre, only a bare and empty room." California Institute of the Arts. Perhaps the most notable modular theatre in this country is found at the California Institute of the Arts in Valencia (Figure 62). According to its designer, Jules Fisher, the structure con sists of a neutral rectangular room, darkly colored, with a flat floor, a level balcony area that extends back from the top of the walls and a ceiling equipped for lighting and the flying of scenery.^2 The major feature of this performance room is the floor, which is divided into a uniform array of square modules 145 146 F I G U R E62 CALIFORNIA INSTITUTE OF T H E A R T S - MODULAR. that can be positioned vertically to form a vast number of audience-performer relationships. The floor is actually a grid pattern of four-foot squares, six-inch-high platforms finished in battleship linoleum. Any one, a combination of many, or all the platforms can be raised above the floor ("zero") level by six-inch increments up to a height of 10'0,T. At any height, the platform can be considered a seating platform, an aisle, a stage or a piece of scenery. As a seating platform, a single unit of two seats is fastened to the platform, facing in one of four directions. In addition, the seats swivel freely for greater freedom of sightline orientation. It is possible to set up the seating in countless combinations with or without any degree of pitch or rake. Since everything sets up without tools, you have the freedom to change the format as often as you wish.33 Each of the four foot square modules is attached to the top end of a large Teflon-coated pneumatic plunger (Figure 63), which fits into a casing that extends down to a floor level below the theatre substage area. Each of the pneumatic plungers has a series of holes along its entire length on six inch centers for inserting a steel pin upon which the unit rests (Figure 64). To raise the module an air hose with a piece of steel tubing attached is first inserted into a fitting in the subfloor, directly under the edge of the platform. Then a valve between the hose and the tubing is opened to pressurize the cylinder and raise the lift. When it has risen to a point slightly above the desired level, the steel pin is then inserted and the air slowly released, dropping the unit down until the pin rests in a slot on the top of the cylinder end cap (Figure 65). 147 148 r / w K t z CflLIFOR.NIft INSTITUTE OF THE ARTS - U N D E fcyiE W O T a F T F LftT F O /Z M S , C ALIFO R N IA INSTITUTE OF 149 C A L IF O R N IA IN S T IT U T E O F TH E A R T S - P L U N 6 E P W I T H S U P P O P P P I N 150 At the edge of each platform, directly over the air fitting, is a removable plug into which the air tubing can be inserted (Figure 66). The floor level directly below the theatre, in the area where the many rows of casings for the pneumatic plungers are located, is very resourcefully utilized as the book stack area for the school library (Figure 67). Although this theatre, with its four foot modules can probably be converted to more staging configurations than any other modular theatre in the country, it does have its share of difficulties. For instance, the actuators in this system suffer somewhat from a characteristic that is inher ent with most pneumatic actuators. It stems from the physical rule that the static friction of a body is greater than its running friction. When sufficient pressure has been applied to the actuator to overcome its static fric tion and start it moving, then the expanding air in the cylinder pushes it along very rapidly, producing uncon trolled jump starts. Also, when the piston is held off of its support pin by air pressure then it tends to bounce up and down somewhat whenever the load on the platform is changed. In addition to these inherent problems, there have been other unforseen areas of concern in this particular installation, such as having the platforms dropped onto their retaining pins with enough force to flare out the pin 151 152 IG U K E ££ CALIFORNIA INSTITUTE OF THE ARTS, - l /f t p la tfo r m s i a / i t f /A /S F R T IU 6 A I F T U B E FOR PLUG 153 ! a r . 9 F I G U R E 6 7 CALIFORNIA INSTITUTE OF THE ANTS p n e u m a tic CYLINDER. L/BPARY) holes, so that on subsequent repositioning operations they have hung up on the cylinder bearings or wiper rings. This could have been resolved by designing the air valve so that it could not vent so quickly, or by chamfering the pin holes, or perhaps adding a snubbing cushion under the pins. Another design problem that has affected the break-out force on the pistons is related to the alignment of the retaining pins with their holes. In this installation the retaining pin slots in the casings are off-set slightly with respect to the holes in the pistons so that the pins will come to rest against one side of the slots to take the backlash out of the system and prevent the platforms from 34 rotating slightly on their axes. In several instances this pin offset has been excessive, and caused the pins to hang-up in their slots enough to require a substantial air charge in the cylinder to release them. If the units are pressurized while in this condition then the platforms, after breaking-out, tend to shoot upward at a very rapid rate, which could cause damage to the system, and certainly to an operator who might be standing on the platform. Therefore, in cases such as these the practice has been to pry the pin loose from its slot with a crow bar before turning the air on. Another problem that has been encountered in this installation arises from the high level of random noise 154 that is generated whenever the audience moves about from the lift modules and such clattering components as the demountable swivel seats, the moveable steel railings, and the numerous fiberglass step units. Also, when the modules are extended to their full height they tend to wobble about a bit, which is quite safe but usually elicits uneasy com mentary from the patrons on the top rows. The inherent sporadic movement characteristics of this type of pneumatic lift mechanism makes it generally unsafe for use during a performance, particularly in those appli cations requiring the elevation of performers or large scenic elements. The use of hydraulic actuators in this type of installation would have undoubtedly produced far superior results, but the cost would be prohibitive. As it is, with over 350 pneumatic actuator modules in the system the cost is still very high compared to other modular theatre arrangements. The time and energy expended in making a major change in the set-up is also substantially greater in this theatre than with other types of flexible staging, which means that changes in the staging layout are made less frequently than might have been with a less ambitious design. All things considered, however, the users of this facility say that it satisfactorily accom- 35 plishes nearly everything that they expected of it. University of Texas. Another modular theatre of note 155 in this country is at the University of Texas in Austin (Figure 68). This is a much simpler and less expensive arrangement than the one at California Institute of the Arts, but it consequently does not have nearly the flexi bility. This theatre, which was built in the early 1960s, has an arrangement of floor modules that are ten feet square and are supported by tubular steel legs at each corner so that they look somewhat like a group of overgrown card tables. The legs of the modules are, in turn, fitted into larger steel columns which are arranged to form part of the theatre's substructure (Figure 69). This area is used for temporary scene storage except when a change in the theatre configuration is undertaken. Then the area is cleared, a section at a time, so that a portable hydraulic lift mechanism (Figure 70) can be wheeled in to raise or lower the module to its new position, at which time an operator installs a steel retaining pin at each leg (Fig ure 71). The portable actuator mechanism has a simple, integrated hydraulic system with a built-in power supply and control valves (Figure 72). This type of installation is relatively inexpensive to construct and operate and is said to be very functional and fairly easy to convert from one configuration to another. Some complaint, however, has been registered that the ten foot square modules are too large to form many desired staging configurations, and also that having to continually 156 157 FIGURE G>3 U N IV E R S IT Y O F T E X A S ' g UNIVERSITY OF ~ MODULAR. TH E A TR E . F / 6 U & E 7 0 UNW EIZ5ITY OF TEXAS' F>0£r/)BLE L/FT M6CAM/SM 159 V I F u _ M i / £ / e s / r v . — 0 P E & A T O & . /a/stallik/6 fc£TA/MlKl<$ /=>/// 160 adapt standardized plywood and scenic elements to fit this , . - i , . . 36 particular modular size is a nuisance. Alternative stage lift mechanisms Although fluid power has been shown to be the simplest and most efficient power media for most stage lift systems it may not necessarily be the best choice for all theatres. In any event it is certainly advisable to explore the salient features of various other types of lift systems before making a final selection. New Orleans Theatre of Performing Arts. One alterna tive approach is to use a rack-and-pinion lift device such as the type that operates the segmented stage lifts at the New Orleans Theatre of Performing Arts (Figure 73). Each lift platform in this installation is supported by two steel columns which are housed in sublevel casings similar to those in a hydraulic system. Each column is fitted with a rack that extends along its full length in a manner similar to the rack-and-pinion stabilizer mechanism pre viously described. The two racks are each engaged with a pinion gear that is connected to a drive shaft, which is turned by an electric motor operating through a worm reduc tion gear (Figure 74). Aside from its basic function of multiplying the force from the motor to the lift columns, the worm gear offers the advantage, because of its inherent frictional characteristics, of not being able to be rotated 161 i H O CO F/6URE 72. UNIVE£SlTY OF TEXAS - Portable N E W O R LEA N S T E E /jT E E O E F , £/S E O /Z M /A /6 ARTS>- EAC /C -A N D - G E A E STAG E L /E F M E C A A N 163 164 F/GU/ZE 74- NEW ORLEANS THEATRE Q F PEFFOF.MIN& ANTS- ELECT N IC . W C E M S E A R . D / Z / t / E M G C H Q E IS M in the reverse direction from a load on the output shaft. This provides a built-in locking mechanism to keep the platforms from slipping downward when the motor is not running. The geared drive shaft also acts as a positive stabilizing mechanism for keeping the platform level at all t imes. The system is reported to function very satisfactorily but it is more complex and costly than an equivalent cable- stabilized hydraulic lift system. It also is noisier and not as smooth as its hydraulic counterpart and it requires substantially more maintenance, particularly in its complex 37 electronic control circuitry. War Memorial Opera House. Another alternative ap proach, similar to the rack-and-pinion method, is to utilize a system of screw-jacks such as the one that drives the orchestra lists at the San Francisco War Memorial Opera House (Figure 75). The orchestra lift system in this installation is divided into three platform segments, each supported by two steel columns with a helix of large square threads cut their entire length. The threads on each column are engaged with a large "nut," which is connected by a drive shaft to an electric motor through a worm gear, in a manner similar to the New Orleans system. With this arrangement the frictional characteristics of the screw mechanism on the columns plus that of the worm gear acts to 165 G.AN F P A N C /£ CO OPE FA - ORCFFSTRA 166 prevent downward slippage of the platforms. This installation has been in service since 1934 and has proved over the years to be very reliable and effective and easily maintained. It was not used for most of the last decade, however, but when it was recently put back into operation, the only servicing that was required was to grease the jack threads and check the electrical compo nents. The main drawbacks of this system are similar to those of the New Orleans system in that it is not as smooth or quiet as a conventional hydraulic lift, and the compo- 38 nents are more costly to make and install. A third alternative method of operation for stage lift systems that is worth considering is that which utilizes a cable lifting device similar to those that were used to raise traps and bridges in many of the nineteenth century theatres. The bridges at Booth's Theatre were undoubtedly raised by such a system and in Edinburgh, Scotland, The Andrew Brown method was in use by 1875. The Hofburg Theatre in Vienna, which opened in 1888, had a system in which "all of the hydraulic pressure was indi rect , the movements being effected by cables and pulleys which were worked by rams placed by the side of the 39 stage.” This was done so that "no blocking of the under stage by vertical rams occurs, as in the case of the 40 ’Asphelia’ system." 167 Westmont lift system. A modern approximation of this scheme that is functioning quite satisfactorily in a number of installations is built by the Westmont Engineering Com pany of Santa Fe Springs, California. Their system differs from the early versions in that it utilizes an electro- mechanically operated cable system that works through a series of telescopic support columns to elevate a stage platform (Figures 76 and 77). In this system an electric motor driven winding drum pulls a series of cables that pass under sheaves at the bottom of struts located at each corner of the lift platform and then go over more sheaves at the top of the struts and back down to the bottom of another set of struts inside the first, and so on, to pro vide an electro-mechanically powered linear actuating sys- 41 tern. This is a relatively straight-forward and inexpen sive arrangement that permits the use of a freestanding structure without the necessity of having sheaves mounted on the pit walls near the upper end of the platform travel. However, it also must be driven through a worm gear reduc tion unit, and has a lower platform stiffness than either the hydraulic or screw-jack systems because of the elastic ity of the relatively long supporting cables. Variations in the elasticity of the four cables also make this system more susceptible to a slight tilting from the horizontal plane than in a conventional cable stabilized hydraulic lift system where only two shorter cables are involved. 168 169 F/6URE WESTMONT C O R P .- CABLE CYLINDER LIFT SYSTEM F/GU/ZF 77 W E S T M O N T CORE. - V/ORM-CrEfi/Z MSCHM/SM 170 Lateral platform movement is also more of a problem in this type of a system because of the increased number of bearings required by the telescopic support columns. The installation at Meramec Community College in St. Louis, Missouri (Figure 78) employs four of these free standing cable actuator lift units to produce a combined 42 orchestra lift-adaptable theatre system. Three large rectangular segments are set side by side across the stage in front of the proscenium line and can be operated indi vidually or together to produce an orchestra pit, an enlarged auditorium floor, an extended apron, or any com bination thereof. In addition, a trapezoidal shaped seg ment is located in front of the center orchestra lift which can be raised from the auditorium floor level to stage level or anywhere in between to create a deep thrust stag ing configuration. The seats in this area of the auditori um are mounted on castered risers so that those on the lift platform can be moved off and stored backstage and the ones to the sides can be pivoted towards the center. The elec tronic control console, which is located behind the stage left proscenium wall, is designed to automatically position the units at any of the three basic elevations, but it can be overridden to stop them at intermediate levels. The lifts have periodically been used during musical productions to raise performers and scenic elements into view of the audience. However, whenever they have been 171 172 operated in this manner it has always been done with suffi cient musical accompaniment or appropriate sound effects to mask the clicking and jolting starts and stops from the single speed drive motors and their mechanical brakes, and the audible whirring noises during the lift movement from the winches and the reduction gears. Also, when the seg ments are at stage level they tend to wobble laterally up to about a half inch of total displacement when pushed sideways. This is not normally troublesome but it does occasionally create some concern among the dancers and other physically active performers. The segments can be shimmed to prevent this movement, but then that precludes the possibility of operating them during a production. The lateral flexibility of the platforms in this installation also has occasionally created minor problems of interfer ence with the pit sidewalls and between segments. In addi tion, on those occasions when a lift segment is used to move very heavy objects such as a seating unit or a large piano organ, care must be taken to center them on the plat form so that the load is uniformly distributed to the four lifting cables. When this was not done a lift segment has more than once developed a noticeable permanent tilt which required a subsequent readjustment of the offending cable to relevel the platform after the load was removed. These few problem areas have apparently not proved disadvantageous enough to outweigh the benefits of the 173 system because the users of this installation profess to be quite satisfied with its overall performance, and the basic concept is gaining acceptance among an increasing number of new theatres throughout the country. A massive lift system of this type is even planned for the Hollywood Bowl in Los Angeles. 174 Notes ^Edwin 0. Sachs, Modern Opera Houses and Theatres (London: Benjamin Blom, Inc., 1896), p. 46. ^Sachs, p . 52. ^Sachs, p . 44. 4 Phyllis Hartnoll, The Oxford Companion to the Theatre, 3rd ed. (London: Oxford University Press, 1967), p. 888. 5 Wilfred Granville, The Theatre Dictionary (New York: Philosophical Library, 1952), p. 179. 6 Roderick Ham, ed., Theatre Planning (London: The Architectural Press, 1972), Glossary of Terms. Also, Hannelore Schubert, Moderner Theaterbau (Stuttgart: Karl Kramer Verlag, 1971), refers to stage lifts as "Podia" throughout the book. 7 Ham, p. 83. Adaptable theatre usage was not in cluded in this delineation. g Many European opera houses, particularly those in Germany and Austria, have a vast repertory of complex works and alternate them each performance. The consequent chang ing of large scale settings at such frequent intervals necessitates the use of a large stage crew and extensive mechanization of the scene handling equipment. 9 The Hippodrome in New York had an immense hydraulic lift that left a huge void in the stage when it was lowered, but the chasm was quickly flooded and used for spectacular aquatic effects. The theatre at the MGM Grand Hotel in Las Vegas has a less grandiose lift system than that at the Hippodrome, but it likewise creates a gaping hole when it is recessed. In this theatre, however, the hole is covered with a rolling platform that moves on from the side of the stage. ^Personal interview with William D. Bell, Sales Engineer, Dover Elevator Company, Los Angeles office, August 1974. Also noted in "Dover Levelator Lift," 175 information pamphlet, publication IE-050, Dover Corp., Memphis, 1973. ^"Rotary Levelator Lift,, r information pamphlet, pub lication RE-195-C, Dover Corp., Memphis. 12 Personal interview with George C. Howard, Theatre Design Consultant, February 1976. 14 Personal interview with Walter Huntoon, Technical Director, Golden West College Theatre, Huntington Beach, California, November 1975. 15 Personal interview with George Gerba, Technical Director, Walnut Street Theatre, Philadelphia, July 1973. 16 Beacon Machinery Company, St. Louis. 17 C. S. Goodale Company, San Diego. 18 Personal interview with William Hektner, Technical Director, San Diego State University, February 1976. The base price of the complete lift unit was $2,300 in 1967, and the total installed cost was less than $7,000. 1 9-ry . , Hektner. 20 Personal interview with the University of Utah Theatre Arts Department, March 1976. ^Sachs, p. 58. 22 Howard. Also from a tour of the MGM Grand Hotel Theatre facility, Las Vegas, October 1974. 23 Personal interview with Ludovicus Schmitz, Assistant Technical Director, Hesse State Theatre, Weisbaden, Ger many, September 1975. 24 Philpot. 25 Personal interview with Rudolph Kuntner, Stage Manager, Metropolitan Opera House, New York City, April 1974 . 26q , Schmitz. 27 Jo Mielziner, The Shapes of Our Theatre (New York: Clarkson N. Potter, Inc., 1970), p. 108. 176 2 8 Jo Mielziner, ed., Theatre Check List (Middletown, Connecticut: Wesleyan University Press, 1969), pp. 14-17. 29 Mielziner, Check List, pp. 24, 25. Also from per sonal interview with the Loeb Drama Center, Cambridge, Massachusetts, August 1974. 30 Personal interview with Fred Kobus, Head Theatre Technician, California State University, Long Beach, Theatre Arts Department, January 1976. 31 Mielziner, Shapes, p. 95. 32 Jules Fisher, "The Modular Theatre, Some Random Notes on the Design, information paper (related to his design of the modular theatre at California Institute of the Arts), California Institute of the Arts, Valencia, California. Fisher. 34 Personal interview with Olaf Soot, Theatre Engineer ing Consultant (designer of the California Institute of the Arts modular theatre lift system), April 1974. 35 Personal interview with Robert Curtis, Associate Director of Facilities, California Institute of the Arts, Valencia, California, February 1974. 36 Personal interview with John Rothgeb, Designer, University of Texas, Austin, Theatre Department, December 1973 . 37 Personal interview with R. J. DeCuir, Theatre Elec trician, New Orleans Theatre of Performing Arts, January 1974 . 38_ „ DeCuir. ^Sachs , p . 57 . 40 Sachs, p. 57. 41 Personal interview with the Westmont Industries, Santa Fe Springs, California, February 1973. 42 Personal interview with John Jackel, Theatre Mana ger, Meramec Community College, St. Louis, March 1976. 177 CHAPTER IV ON-STAGE MACHINERY Wagons and Revolves One of the most effective and least expensive ways of shifting bulky or heavy scenic units is with some sort of moveable platform, the simplest of which is the ubiquitous stage wagon.^ Stage wagons come in a wide variety of sizes and shapes and can be made to move freely in a random pattern, to run in a straight line or curved path when constrained by a set of guides, or to travel in an arc like a jack-knife or segmented stage when secured by a fixed pivot. They are usually designed for moving scenery across the top of an existing stage floor, but occasionally are built-in as an integral part of the stage. Most wagons roll on rubberized wheels that are either fitted to swivel ing casters which allow steerage or to fixed carriages which restrict the nonlinear travel of the wagon. Very large, heavy wagons are often carried on steel wheels that run on tracks built into the stage. However, this fre quently generates the accompanying liability of an audible rumbling noise when the unit is in motion. Pneumatic casters, or "air bearings" have been receiving increased attention in recent years as a practical method of 178 supporting stage wagons. Revolving stages, which essentially are nothing more than circular wagons that are confined to a rotational movement about a central axis, also come in a wide variety of sizes and can either be built-in or laid on an existing 2 stage floor. Concentric revolves, which consist of a revolving unit with a larger annular shaped unit surround ing it and rotating about the same axis, permit the con current movement of different parts of a setting, either in the same or opposite direction. Most discs are mounted on fixed rubberized wheels that may or may not run on a track laid on the stage floor, depending upon its relative smoothness. Large revolving stages are usually carried on steel wheels because of the immense weight factors in volved. The use of air bearings is also currently being explored as a support medium for discs and revolving stages. Most discs and on-stage wagons are light and manageable enough to be moved by hand, but heavy or bulky units often need the assistance of levers or windlasses to 3 overcome the starting friction. Exceptionally heavy or cumbersome on-stage units as well as most revolving stages and built-in wagon systems usually require some form of power operation, particularly where precise control, remote operation or large driving forces are a critical design factor. The majority of these systems have historically been driven by electric motors, partly because of the 179 predominance of electrical technology among the equipment designers, and partly because of the relative ease with which electric drive mechanisms can be fitted on-board the moveable platforms. Munich Staatstheatre There are some notable exceptions in the use of stage wagons, however, in which they have been very successfully operated by fluid power. Several theatres in Germany have long been using hydraulic actuators to shift hugh stage sized wagons, replete with immense architectural settings. The Staatstheatre in Munich, for example has a system of hydraulically powered stage trucks which can be rolled onto the mainstage area. Each of these wagons is driven by a large hydraulic cylinder, two of which are mounted verti cally on the side walls of the stage house directly behind their respective trucks, and the third located under the floor in the up-stage storage position. They are connected to their loads by a healthy cable-roller chain arrangement that allows the wagons to be driven in both directions. The installation is powered by water pressure which is controlled through a simple four-way valve mechanism con nected to each actuator. The system has been operating satisfactorily for many years and is reported to be very 4 dependable, and requires minimal maintenance. 180 New Orleans Theatre of Performing Arts A modern variation of the hydraulic powered wagon con cept can be found at the New Orleans Theatre of Performing Arts. This theatre utilizes a T-shaped stage layout some what like the conventional German approach, except that the side and rear storage areas are smaller and not partitioned 5 off with soundproof doors. Also, the wagons are not hugh single built-in units but are assembled as required for each production out of groups of smaller, rubber castered segments that can be pulled on or off stage by a series of clevis drive mechanisms which are recessed in long slots cut into the stage floor. There are five such drive mechan isms in each of the three off-stage storage areas. Each is enclosed in a floor-trap compartment beneath its respective clevis slot, with the side-stage units moving parallel to the curtain line and the up-stage units traversing up and down stage. Each of the actuator mechanisms consists of a thirty foot hydraulic "cable cylinder," an actuating device that is similar to a conventional double-acting balanced cylinder except that instead of having two equal diameter piston rods it utilizes a pair of nylon-coated steel cables. One cable is attached to each end of the piston and passes down its side of the cylinder, through the end seals, around steel sheaves fitted to the ends of the cylinder to the drive clevis, which forms the "dog-and- 6 slot'T attach linkage for the wagon units (Figure 79). 181 C O M B /A /E D E N O C A F > - S H £ A 1/E B L O C K UPPER C Y L IN D E R . P O E T C Y L ! N D E K P /S T O N fZ E L lE F M L V E X LO W E R CYLlNDER P O R T S H E A V E CL EVJS N Y L O N C O A T E D C A B L E P /S TO N P O L O F /G U /Z E 7 9 HYDR.fi FLOAT - CABLE C YL I N D E /C A S S E M & L Y 182 This arrangement produces a linear hydraulic actuator with a total operating length that is very little longer than its twenty-nine foot stroke, which is the maximum required travel of the wagon units. By contrast, a conventional balanced hydraulic cylinder would have required a floor trap compartment length approximately three times the maximum wagon travel, or a shorter actuating cylinder with a complex double or triple purchase linkage between the actuator and the wagon engagement clevis. A single vari able displacement power supply is used to provide a con stant pressure of about 1,500 psi to each of the 15 actua tors in addition to a complete set of hydraulically driven fly lines. The wagon drives and overhead rigging actuators are designed to operate as an integrated system and are controlled from a remotely located console on the stage floor. The complete installation, which is known as the "Hydrafloat System, " will be discussed at length in the following chapter. Each of the wagon drive actuators are capable of generating a horizontal force of up to 2,000 pounds against a static load to get it moving, and then smoothly and quietly accelerating it to a maximum speed of five feet per 7 second. Smooth deceleration and positive holding in a fixed position are also easily accomplished through the closing off of the flow of fluid to and from the respective actuators, which is done automatically at the control 183 console. The various wagon units also can be moved on and off stage either as a group, individually, or in any desired combination of cross-shifting. The system has been in service for several years and is considered by the g users to function very satisfactorily. However, the basic type of operation under which the theatre is currently being used does not lend itself to productions in which many power driven wagons are required. Consequently, the system has not had sufficient use to determine its long range operational characteristics. In fact, the basic cable cylinder concept as a whole has had so little use in the fluid power industry that reliable performance data or 9 service histories are generally unavailable. In addition to its relatively simple, compact design, this type of mechanism offers the usual hydraulic linear actuator advantages of smooth, quiet operation, high driv ing forces, precise control, positive braking and holding, and moderate cost. The operation of these wagon drive units is reported to have thus far revealed no major func tional difficulties. However, there are a few potential problems areas that should be taken into consideration. The first area concerns the difficulty of maintaining a minimal, near zero leakage rate between the cylinder end- seals and the nylon coated cables. Any slight cut or abrasion of the nylon coating could create an intolerable leakage condition that would require the replacement of an 1S4 entire cable. The problem is compounded by its moderately high operating pressure (1,500 psi),"*"^ and is further ag gravated in this installation by the exposure of the ex ternal portions of the cables to whatever grit and foreign obstacles may fall through the floor slots. Fortunately, fluid leakage from an actuator in a horizontal movement mechanism is not as critical as in a hydraulic stage lift or an overhead rigging system because the weight of the mechanism and its attached scenic element is supported by the floor and does not act against the seals while resting in its static position. About the worst that would happen from leakage in this type of wagon drive system is that a little fluid would be lost and a small mess made, as opposed to a vertical lift system where leakage would cause a static load to slowly drift below a preselected elevat ion. Another problem with the cable cylinder concept con cerns the possibility of the nylon eventually separating from the cable because of the stress that is generated at the bonding surface as the cable bends around the end sheaves. This condition can become particularly acute during heavy loading situations when all of the force of the pressurized piston is being transmitted through the cable in tension and bearing around one of the sheaves. These potential problem areas have not yet caused any par ticular operational difficulties during the five years that 185 this installation has been in service, except for a few cases where the nylon coating has been gouged or sliced by sharp objects coming in contact with the cable.'*''*' However, there remains a reasonable probability that these factors may yet cause significant increases in the basic mainte nance and repair costs of the system in future years. Perhaps a more suitable method for powering built-in revolves and wagon drives might be to employ rotary actua tors, i.e., hydraulic motors, rather than linear actuating cylinders. Hydraulic motors are more logically suited for many horizontal movement applications than either linear actuators or electric motors because they have proved to be very rugged and durable while offering the same force, speed, and control advantages as hydraulic cylinders, and yet are more compact and adaptable to cramped or isolated installation situations than most comparable electric drives. Also, the two major disadvantages of hydraulic motor usage in stage work can be effectively nullified in this type of horizontal movement application. First, motor creep, a condition that is common to most hydraulic motors because of their inherent internal leakage characteristics which results in a slow rotation of the motor output shaft under an externally applied load when the outlet port is blocked, does not come into play here because the horizon tally moving stage equipment does not normally bear against the motor shaft when the units are at rest. Secondly, 186 since the drive units are normally recessed in compartments below the stage, it would be a relatively simple matter to enclose the units in a sound-isolating chamber with only the output shaft with its drive sheave or sprocket protrud ing. Hydraulic motors are not well suited to wagon drive applications where the driving units are carried on-board the moving structure because of the lengths of relatively cumbersome flexible supply and return hoses that would be required to extend from the wagon to the stationary power supply. They can be mounted on-board revolves, however, by using swiveling hydraulic fittings at the rotational axis of the revolve in the same way that electric motors mounted on-board revolves draw their power from electrical slip rings. The issue essentially is moot, however, because there would be little point in mounting a drive mechanism on the revolving part of the structure when it could as readily be secured to the part that is fixed to the stage floor. University of Texas One of the most effective uses for hydraulic motors in the theatre is as the driving mechanism for discs, or on-stage revolves. The Theatre Department at the Univer sity of Texas at Austin has constructed an excellent example of a portable hydraulic motor driven disc in their 187 own theatre shop. It is about seventeen feet in diameter, but can be disassembled into eight truncated pie shaped segments plus an octagonal center piece for easy transport and storage (Figure 80). The center piece carries the rotational pivot bearing which was adapted from an old Volkswagen wheel bearing-brake drum assembly. Each of the segments has a two inch steel channel framework around its perimeter with a three-quarter inch plywood panel attached to form the top. Fixed steel casters are fitted to the segments near the outer perimeter to carry the weight of the disc and its stage setting. A steel flange in the shape of an arc is welded to the underside of each segment near its outer edge (Figure 81). When the unit is assem bled, the eight flanges fit together to form a ring which is engaged by the rubber drive wheel on the motor drive assembly (Figure 82). The motor drive assembly consists of a small commercial rotary hydraulic motor that is mounted on a plate and connected through a roller-chain to the rubber drive wheel. The wheel is held securely against the disc flange by a spring-loaded tensioning device. The power supply for the system consists of a reservoir, a fixed displacement hydraulic pump that is belt-driven by a one horsepower electric motor, a relief valve, and a pressure gauge (Figure 83). This is contained within an enclosed wooden box which is fitted with enough flexible hydraulic hose that it can be removed from earshot of the 188 FIGURE 30 U N IV E R S IT Y A T TEXAS - HYPGflULtCALLY DRIVEN — ------------------ D /S C S E £>//)£N T 190 « l * F IG U R E & I UNIVERSITY O r TEXAS - u n d e f l v ie w o f hydr.a u u c a lly d/zh/ e n d /s c m e c h a n i s m H CD H1 F I G U R E & Z (JNWEfZSlTV OF TEXAS-HYP/ZEULIC/IUY D/ZiUEN Oise 0JZIVE MECHMISM UNHIE&SITY OF TEX/9S- NYDRflUL/ CflLLY DZtVEN DISC “ P O W E R . S U P P L Y 192 audience. The control mechanism consists merely of a manu ally operated four-way valve that is mounted in its own portable wooden box (Figure 84). The users of the system report that it easily and quickly moves very heavy loads with smooth, accurate starts and stops. They also report that the noise level of the rotary hydraulic motor is less than that produced by the casters on the disc, which they say is quite acceptable.^ Air Bearings A major advancement that has recently been implemented in the powered movement of stage wagons and discs is to support them by pneumatic casters, or air bearings, instead of wheels. Air bearing platforms were introduced into the theatre nearly a decade ago, but their use has been largely confined to random experimentation because of the general state of ignorance, inexperience, or provinciality within the technical theatre community at large. Most of the work that has been done thus far has been related to the move ment of wagons, but a few notable experiments have been 13 undertaken in the turning of discs. Air bearings are an outgrowth of industrial air film technology, and operate on the general principle that a heavy object can be lifted and transported on a film of air at a relatively low pressure if it is distributed under the object around enough area. Although air bearings are 193 F /G C /£ £ 8 4 UN IU S /Z S /T Y 0 E T E X /IS - h y d & a l/l/c /jlly d ziven d/sc c o n tr o l e>oX 194 made in a wide variety of designs and configurations the most common forms consist of an aluminum disc with a pliable elastomeric "donut" stuck to its underside (Figure 85). Air enters the enclosed chamber through a fitting at the upper edge of the disc and flows out through a ring of holes in the elastomer near the center of its underside and then escapes between its lower, outer edge and the surface upon which the unit rides. The trapped air creates a lift ing force under the bearing equivalent to its gauge pres sure times the area of the bearing against which it is pushing. A twelve inch diameter bearing which is fed from a supply of air at 10 psig is thus capable of supporting about 1,000 pounds of load while offering practically negligible frictional resistance to its horizontal move ment; that is, for every 1,000 pounds of load being lifted, 14 only 1 pound of force is required to move it about. The large capacity of air bearings is also achieved with a correspondingly broad load distribution on the stage floor, an amount which is equal to the air pressure being supplied to the bearing times its contact area with the floor. Wheeled casters, on the other hand, must transmit their load through the comparatively small segment of wheel tread that is in contact with the floor. The broad load distribution characteristic of air bearings permits the use of relatively soft flooring materials, which can be highly advantageous in many types of stage productions. 195 FI6URE 8 TYPICAL AIP. BEAMN6 The amount of air that is consumed by a set of air bearings depends upon the load that has to be lifted, the roughness of the running surface under the bearings, the distance to be traversed, and the frequency of operation. However, an air bearing system for an average stage plat form application should be able to operate on as little as a six or seven cubic feet per minute shop air compressor. An air receiver is also required, along with a pressure reducer, control valves, and sufficient air hose to reach from the compressor outlet to the extreme on-stage position of the platforms. Besides being able to support massive loads with negligible friction, the operation of air bearings is near ly silent when moving over smooth, nonporous surfaces. Stage units that are supported by air bearings also have the freedom to travel in any horizontal direction without restraint because they have no fixed wheels, or casters that must be swiveled before a change in direction can be executed. However, this feature may in certain applica tions actually be a disadvantage, particularly where a rigidly prescribed movement pattern is in order. In these cases it may be necessary to use a guide track system, or even to install a wheel or two into the wagon merely for 15 steerage. Another major advantage of the air bearing concept involves the practical requirement of keeping wagons or discs from shifting about after they have been moved into their playing position. This task, which can be formidable with wheeled units, is easily accomplished with air bear ings simply by deflating them until their built-in static support pads rest firmly on the floor. It must be remem bered, however, that during inflation of the bearings the wagons or discs will rise as much as one half inch, which may occasionally become a design problem. This is gener ally but a trivial annoyance, particularly when it is also noted that heavy wagons and discs can be constructed with a much lower overall height with air bearings than with large diameter, heavy duty wheels. This low profile capa bility can also be very advantageous when it comes to moving and storing a large number of otherwise bulky plat form segments within limited quarters. It is also possi ble to design air bearing platforms so that the bearings can be easily removed for inspection, repair, or transfer to another unit, even when the platforms are in service, loaded with scenery. Perhaps the most important disadvantage of air bearing stage units involves their tendency to shift their atti tude slightly from the level as concentrated loads are moved from one location to another on the platform. When a heavy load is moved from one location to another on the platform the unit sinks a little in that area and rises correspondingly on the opposite side. Sufficient air must, 198 therefore, be provided to the system to insure that those bearings under the concentrated load, wherever it may move, do not "bottom out." Also, if any bearings on the opposite side of the platform are lifted too far off of the floor its elastomeric "donut" will lose the ability to retain air and it will start oscillating rapidly as the air begins to escape in larger quantities. This "fluttering" condi tion may not be particularly harmful to the bearing, but it does cause an inordinant consumption of air and makes a highly annoying and unacceptable noise. The use of air bearings on stage platforms, therefore, always should be undertaken with a consideration for the expected load distribution and how it will be moved about on the unit. If the expected loads are fixed in a stationary location on the platform then bearings only need to be placed to sup port the specific loads plus the tare weight of the plat form, but if the loads will be moving then enough bearings must be used to support the worst load conditions over the whole platform area. It is feasible to incorporate a valving system in the platform air distribution manifold that would reduce the supply of air to the unloaded bear ings, but the added expense and complexity of such a device normally would not be warranted. In general prac tice the number and size of the bearings to be used should be kept to the minimum, consistent with the maximum load requirements because each additional bearing used produces 199 an additional demand on the air supply, which may already be limited. The problem of a limited air supply can be alleviated by adding another off-stage compressor to the system. A more practical approach probably would be to add as large an air receiver as is practicable to the supply line, preferably as near the stage units as pos sible. This would allow the shop compressor to store up an additional supply of air at normal shop pressure while the units are resting on their stationary support pads. Most scene shifts take only a few seconds, which generally is well within the capability of a fully charged theatre shop air receiver of reasonable capacity. Likewise, the time between shifts normally is adequate enough for the receiver to be recharged. The characteristic "umbilical” air supply hose trailing from the platform is a minor annoyance that normally must be lived with. In certain applications, how ever, an air tank and control valve mechanism could be mounted on-board the platform which would supply the pres sure and control functions for a shift or two. Another problem that must be contended with in the use of air bearings is that of excessive air consumption and the accompanying audible "whoosh" when the units run over an uneven, cracked or slotted, or highly porous surface. The usual remedy for this situation is to cover the stage with linoleum or masonite and then tape the seams. A varnished or painted stage will often provide an adequate 200 running surface by itself with only the trap and lift cracks taped. Although air bearings are basically intended for use on smooth, level floors they can generally accommo date a slope of up to five percent with ease, and many of them can surmount projections above the floor surface of up to one half inch, provided that the obstacles are faired into the floor with suitable materials so that the result ing ramp angle is no greater than ten percent. Steps of up to one half inch can frequently be negotiated if they are faired to fifty percent or less . Steps of less than 16 one-sixteenth inch can be disregarded. The escaping air from under the bearings also tends to make them essentially self-cleaning since most of the dust and grit that would normally accumulate around them during the run of a show is blown away whenever they are shifted. In terms of maintenance and service life the record seems to be good. One manufacturer claims that their sys tem requires virtually no maintenance since the con trol valves, of non-corrosive materials, are in most cases the only moving parts. The bearings are easily repairable and replaceable. Histori cally, units have shown no measurable wear or material degradation after years of service.^ Air bearing stage platform systems are more expensive and complicated than a comparable set of manually operated castered wagons or discs, but they also offer several sub stantial advantages, and the price is very reasonable in 201 relation to most other forms of power operated scene shift ing machinery. In any event, the price of individual bear ings is probably within reach of most budget minded theatre operations, and most of the remaining components required for a system should already be available as part of the normal air supply of a properly equipped theatre shop. Also, the required technology is relatively simple, so that almost any theatre shop should be able to develop their own system of air bearing platforms. Pacific Conservatory of the Performing Arts The Pacific Conservatory of the Performing Arts in Santa Maria, California has developed a seventeen foot diameter turntable for a production of "Peer Gynt." It was supported by eight twelve-inch diameter Air Float air bear ings mounted upside down in a stationary framework which rests on the stage floor. With this arrangement the hose that supplies the air for the system remained in a fixed location, thus freeing the turntable to move with no con straints through a full 360 degree of rotation. They were able to "turn six to ten people on the table depending on their spacing” at a lift pressure of six or seven psig, and "had achieved a silent, rock solid, floating turntable 1S that would indeed start and stop on a dime.” Tyron Guthrie Theatre Probably the most extensive use of air bearings on the 202 American stage has been at the Tyron Guthrie Theatre in Minneapolis. Most of the scene shifts in this theatre must be done on wagon units because of its deep thrust stage, restricted up-stage opening and absence of fly- space. Also, its intimate, three-sided seating arrangement imposes a demand for highly detailed, three-dimensional structural settings, which are best mounted on moveable platforms. They initiated the use of air bearings in their platform units about a decade ago in order to overcome some of the inherent drawbacks of conventional casters, i.e., noise, swiveling, high wheel load density, and ineffective 19 braking. A typical setpiece at the Guthrie Theatre consists of large, usually impressionistic forms mounted on a wagon (Figure 86). The setting for the production of Oedipus Rex, for example, was made of fourteen gauge cold-rolled steel, flame-cut and welded into a large unit structure. The framework for the integral base, or "wagon" portion was made of welded two inch square steel tubing, which also acted as the conduit for the twenty-two inch diameter air bearings that were fitted to the bottom of the frame at five locations (Figure 87). Air for the system came from a long hose connected to an off-stage air tank, which, in turn, was fed by the shop air compressor. The floor of the stage was covered by linoleum to provide a smooth, sealed running surface with no cracks which could rob air 203 F/6V/ZE TYRONE 6UTHRJE THEATRE- fl/N. &earjng wagon i 205 from the bearings. The relatively soft linoleum surface was also beneficial in reducing the noise from the movement of the performers and in improving the dancing surface. The total weight of this wagon was nearly four tons, yet it was quickly, quietly, and accurately moved on and off stage by one or two stage hands. Because of the extremely high load carrying capacity and lack of breakout and running friction of this type of wagon system, the Guthrie Theatre has generally adopted the use of air bearings as their primary means of moving set peices. They have likewise given over most of their conventional lightweight theatrical set construction tech niques in favor of much heavier but stronger and relatively less expensive methods. For instance, most of their set pieces are now made of square steel tubing welded into a framework to which quarter-inch plywood is attached with sheet metal screws (Figures 88 and 89). This method pro vides a very rigid structure for hanging bulky facings or applying heavy built-up or sprayed-on surfaces (Figure 90). Their technical director maintained that in many instances these construction techniques have reduced their fabrica tion costs by as much as two-thirds over their previous methods.^ The most important benefit to be derived from the use of air bearings may be found in their great load carrying capacity and its resultant liberation from the traditional 206 F /G U E E Q TYRON GUTMEI E THEATRE- SEr c o a / s r/sc/ct / o a / ----------- \ 208 ■ FI6UHE 89 TY/EON BUTHRJE T H E A T R E - SET CONSTRUCTION , WALLS R 1 G U R . E TYR.ON 6 UT BK1 J L TH EATR E — CO/VST/ZUCT/ON F flC tm S weight limitations on the construction of scenic elements. This factor has opened the way for experimentation with new construction materials and techniques, such as spray-on mastics, featherweight gunite, straw-reinforced plaster, etc.; materials that may weigh heavily, but are very cheap, rugged, easily applied, and produce interesting shapes and textures. 210 Notes “ ^Harold Burris-Meyer and Edward C. Cole, Theatres and Auditoriums (New York: Reinhold Publishing Corp., 1964), p. 313. 2 Burris-Meyer and Cole, p. 313. We are reminded that, technically speaking, the term "revolving stage" is reserved for those types of units that are constructed as a permanent part of the stage and are recessed so that the top of the revolve is level with the rest of the stage floor, while the more-or-less portable units that set on top of an existing floor are referred to as "discs." These definitions henceforth will be honored in this study, except when a reference is made to revolving stage mechan isms in general, in which case the term "revolve" will be used. 3 Burris-Meyer and Cole, p. 313. 4 Personal interview with Helmut Grosser, Technical Director, Cologn Municiple Theatre, Cologn, Germany, September 1975. ^Grosser. 6 William Cruse, "Hydraulic Rigging," Theatre Crafts, 4, No. 2 (1970), 20. 7 Personal interview with William Cruse, Designer of the Hydrafloat System, Los Angeles, August 1973. ^DeCuir. 9 The designers of the Hydrafloat System maintain that the cable cylinder concept was originally developed for an aerospace application. However, inquiries by the author with several aerospace firms and hydraulic equipment manu facturers failed to pinpoint the specific installation, nor could any useful information related to its design or per formance characteristics be located. This type of actuator is also said to be used in a few industrial applications, but concrete evidence there also could not be found. ^Normal aerospace practice limits the maximum 211 acceptable leakage rate for conventional hydraulic cylin ders to about one drop in twenty-five full cycles of actuation. In most instances it has been found that rod seal leakage occurs about as often at atmospheric pressure as at intermediate or high pressures. However, in a system of this type a considerable flow of fluid could result at 1500 psi as a cut or abraded portion of the cable passes across the lip of the seal. "^DeCuir . ■^Rothgeb. 13 The most notable example of an air bearing disc installation is at the Pacific Conservatory of the Per forming Arts, which is discussed later in the chapter. 14 "Air Bearing Catalog," Airfloat Corp., Santa Barbara, 15 "Air Bearing Catalog," p. 4. 16 "Air Bearing Catalog," p. 4. 17 "Air Bearing Catalog," p. 3. 1S Pete Davis, "Upside Down Airbearings," Theatre Crafts, 10, No. 2 (1976), 64. 19 Personal interview with Richard Tidwell, Technical Director, Tyron Guthrie Theatre, Minneapolis, August 1973. 20Tidwell. p . 4 212 CHAPTER V OVERHEAD RIGGING SYSTEMS Vertical movement by means of an overhead rigging system is by far the fastest and easiest method of changing scenery.^ Overhead scenic pieces as well as many on-stage architectural elements and structural units can be flown in or out in a fraction of the time that it would take to move them on or off from off-stage or below-stage positions. Also, flying is frequently the only practical means of dis playing those scenic elements that occupy the large volume of space over the performers' heads. The ease and rapidity with which scenes can be changed by flying also encourages the use of more elaborate and greater numbers of scene changes in a given production. It is not uncommon in theatres with a fully equipped counterweight rigging system (Figure 91) to employ thirty or more sets of fly lines in a single musical production and over fifteen sets in an 2 elaborate drama. In addition to the great effectiveness of the flying mode of scene changing the presence of a fly loft in a theatre is in itself a considerable asset because it also provides an excellent storage space for copious amounts of cumbersome flats, drapes, scenic elements, and 3 lighting equipment. 213 HEAD BLO CK G R . I D L O F T B L O C K — 1 (3 PLA C E S ') S/JO/zr £~/A/£z -CFAlTEfZ C/A/E LOA/6 L . / N E COUNTED. WEIGHT A/E&O/Z LO C /C /N G P A U L P I P E — B A TTEN P O P E LOCK <£ S A F E T r P /N G TENSION BLOCK F/GU/ZE 9/ TYW CAL C O U N TTTW T/G H T lzJ gq/N G LA YO U T 214 The many benefits of a good flying system are not had without their due cost, however. In complex productions where several pieces must be flown in a single shift the operation can become very busy and the manpower require ments extensive. In large repertory theatres and opera houses as many as fifteen frantic flymen may be required 4 for one production. The weight of the scenery is also a prominent factor. In large professional theatres scenic pieces weighing as much as 1,000 pounds must often be flown. To do this with a conventional counterweight system usually requires that the load be attached to two pipe battens, with as many as six men pulling on the counter- 5 weighted ropes . Even the loading and unloading of the counterweights can constitute a major burden. In very large theatres such as the old Metropolitan Opera House, where up to three productions must be mounted and struck in one day, between fifty and one hundred tons of weights may 6 be manhandled in the operation. The power operation of overhead rigging, therefore, offers great potential for significant savings in manpower as well as increases in operating efficiency and perfor mance capabilities over conventional manually operated flying systems. Unfortunately, most power driven systems of the past have either not performed well or have been excessively expensive and complicated, and frequently not very reliable. As a result they are seldom used in modern 215 theatres, and then usually only in opera houses and reper tory theatres of the largest scale, or in a few affluent or daring educational institutions. A review of several motorized flying systems that have been used in the United States and Europe has revealed some basic perameters that define the general criteria for a 7 good power operated rigging system. 1. Adequate load capacity of the pipe battens or spot lines. 2. Good full-load starting and running characteris tics, i.e., no sluggish, rapid, or jerky starts or stops. 3. Adequate speed control, particularly at slow speeds. 4. Adequate maximum lift speed. 5. Ability to run sufficient battens concurrently. 6 . Ability to make sequential lifts, i.e., piling-on additional battens during a movement sequence. 7. Ability to move several battens simultaneously, each at different speeds. 8 . Ability to move several battens of different weight in synchronization. 9. Adequate repeatable trim height positioning tolerances. 10. Positive braking and holding. 11. Minimal noise. 12. Failsafe, foolproof design minimizing the risk of 216 inadvertant operation or dropping of a load. 13. Overload or fouling protection, i.e., adequate load sensing devices to stop a batten if it should foul a neighboring piece of scenery. 14. Ease of operation and maintenance. 15. Availability and reasonable cost of replacement parts. 16. Good reliability and service life. 17. Reasonable initial cost and overall operating expense. Metromatic Loft System The electrically powered flying system in this country that probably comes closest to meeting these criteria is the ’’Metromatic Loft System,” which was designed and built by the Peter Albrecht Corporation and installed at the Metropolitan Opera House in 1966. This system employs a total of 109 parallel pipe battens on 5-1/4 inch centers, plus 8 spot lines. Each of the battens is capable of lift ing a maximum payload of 1,000 pounds from the stage floor to the grid, 108 feet overhead, at speeds up to 3 feet per second. They are powered by individual five horsepower, variable speed, DC motor driven winches, which, in turn, are connected to terminals in a patch panel located on a raised platform overlooking the stage floor. The power source for these winches consists of 30 440 volt, 3 phase, 217 silicon controlled rectifiers located in the basement, each of which is connected to a jack handle in the patch panel that can be mated with any of the winch terminals (Figure 92) . The control console for the system is located on the raised platform, on the downstage side of the patch panel. It has thirty control station panels, one for each of the power supplies, plus six master stations which are used for running multiple batten groupings. Every control station has a spring-centered operating lever that, when pushed up or down, moves a batten up or down correspondingly, at a speed approximately proportional to the return force on its centering spring. This provides the operator with a degree of MfeelM for the speed that a batten is traveling. The running speed of the pipe battens is regulated by a dial on the control station to which it is patched. There also are two digital type batten positioning presets on each control station. The lower one is for the working, or "in” posi tion of the battens and the upper one is for the storage, or "out" position in the fly loft. When a batten, travel ing either in the up or down direction, moves within a pre determined distance of one of the preset positions it automatically slows down and stops within one-sixteenth inch of the desired trim height. Any or all of the control station battens can be set to travel at different speeds to different trim heights and then can be switched to one or 218 $r4&S£&£p Her/to plucacs L-o p t ac/cs 3 E D Q DC MOTO/Z D&ll/£M HOtST f 09 UNITS ~ P L U G £rtCLOSCJ& £ B O R£71Z/ICrAW£ PLUG S I PDI LFtHL^LPLP U* IMlro O o o o c > o oooo P A T C H °%aa PA H S L Oo 103 K£C£Pr/?CC£S COrtT/ZOC C O N & O L S •30 STATIONS 2L M A G T &&S am /m potA/erR . 4-+OV. 3 P S C p. e e c t / e /e r . p m el s ■30 U N ITS P / C U R . D 9 2 M e r f e o / w t r / c l o f t s y s t e m l./?your 219 more master control stations so that they will all go their own separate ways upon the movement of the respective mas ter control levers. In addition, the whole group can be regulated by the master speed control to travel at propor tionally slower speeds than are shown on the respective control station settings, so that shifts can better be timed to match the prevailing tempo of any given produc- 8 t ion . This system was developed to meet the stringent per formance criteria and continuous hard use imposed upon it by the intense production schedule of the Metropolitan Opera. Rudy Kuntner, their stage director, emphatically maintained that in comparison to their old manually operated counterweight system it Mis advanced as we have found that we can use . . . the layout is very good, and it 9 does our job very nicely.” The design was not achieved without considerable dif ficulty, however. The low speed, full load operation was found to be a critical design obstacle for the worm reduc tion gears as well as for the SCR control devices, particu larly in the downward direction of travel where the loads are regenerative (applied in the direction of movement). Weight and space was also a problem. The hoist units alone added over eighty tons of weight to the gridiron, which had to be accounted for in the reinforcing structure of the stage house. The winches, which wind seven batten cables 220 each on a drum two feet in diameter by three feet long, had to be placed in three staggered rows along the side wall at the grid to accommodate the five and one-quarter inch batten spacing. Special head blocks also had to be designed into a staggered single-sheave arrangement in order to direct the cables properly toward the drums. The patch panel also consumed much valuable back stage space because it had to transmit directly the full DC power from the rectifiers to the winch motors. With respect to the overall operation and maintenance of the machinery in the theatre Mr. Kuntner expressed some regret that in this opera house I got too electrical . , . I do not mean that the electrical equipment doesn't do the job, but it does mean that you must have for the theatre, which is a repertory house, time to maintain the equipment.^ The maintenance time in this case means an average of about one full day each week, when the production schedule allows. This installation satisfactorily meets most of the previously outlined parameters of a good powered fly system except that there are no automatic antiscenery fouling pro visions. The operators must pay very close visual atten tion to the moving battens to see that they do not inter fere with any adjacent obstacles. In this respect, the only operators who are allowed to operate and maintain the fly system are a few well trained, highly competent tech nicians who are thoroughly familiar with the machinery as 221 well as with the overall flying requirements of the Metro politan stage. The theatre management could not afford to leave the system in the hands of students or partly trained personnel, even if it was designed to permit it. Another factor in this system that might affect a decision to install a similar one in many other theatres is the initial expense. This system cost $730,000 installed in 1966.^^ It is basically a prototype system, however, and much of the developmental expense has thus been written off. Similar installations on a smaller scale have subsequently been completed at figures of less than one-third that of the Metropolitan installation. The manufacturer maintains that, in general, "the costs vary anywhere from twice the cost of a compound rigging manual counterweight system, to four or five times the cost of 12 such a system." On the positive side, they also cite a study which shows that in five or six years the wages saved by using fewer stage hands for set-up and take-down (in a large professional theatre) pay for the extra cost of the system, to say nothing of the addi tional use of the facilities.13 Synchronous Winch System Another type of electrically powered flying system that is worthy of consideration as a competitor to fluid technology is the "Synchronous Winch System" which was designed by George C. Izenour of Yale University and first 222 installed at Hofstra College in 1959. A few other instal lations have since been made at such schools as Harvard University, City College San Francisco, and at the Univer sity of California at Los Angeles. The performance of the various installations has not produced entirely satis factory results, however, and the design has subsequently 14 been discontinued. Most of those installations which are still in use have experienced operational difficulties in such areas as maintaining uniform lifting speeds over a wide range of loads, handling multiple groupings of scenery, and in position monitoring and travel limiting 15 functions. In spite of its various operational defi ciencies the general concept is relatively effective, how ever, and satisfies most of the demands of the educational theatre programs for which it was intended. Some of the installations have even been upgraded over the years to overcome or at least minimize many of their original prob lem areas. The system at UCLA, for example, has recently been modified to incorporate a completely new, highly sophisticated, digital control console with a built-in memory feature. The main idea behind the Synchronous Winch System departs from the conventional counterweight rigging concept in that it does not employ the usual arrangement of parallel pipes and sets of permanently located stage lines but instead uses a system of "spot-lines" which can be 223 positioned anywhere around the stage as needed (Figure 93). Each line runs from its own individual hoist mechanism at the edge of the grid, across to a sheave on the grid, and down to a load on the stage floor. The sheave is moveable and can be easily secured to the gridiron at any desired location. Each hoist mechanism consists of a one horsepower synchronous motor that is geared to a drum wound with enough stainless steel aircraft type cable to traverse the extremes of the grid and drop down to a load on the stage floor. An electrically controlled braking and holding device is included as well as an electronic transducer which measures the position and travel rate of the hoist line, and an adjustable safety limit switch mechanism that is supposed to stop the hoist at any desired upper travel limit in case of a malfunction of the primary travel limiting circuitry. The central power supply, or "master drive unit" for the hoists consists of a twenty-five horsepower AC induc tion motor that is electronically clutched to a synchronous alternator of similar size. The synchronous alternator is an alternating current generator whose output frequency is variable and is used to provide precise speed control for whatever synchronous motors that may be connected to it. At the University of California at Los Angeles installation there are fifty individual hoist mechanisms and two master 224 G R ID L E V E L SO SYNCHRONOUS H O /S T U N IT S STAGE L E I/E L c o n t r o l c o n s o l e SO STATIO NS D f Q L EH B A S E M E N T LEVEL 2 SYNCHRONOUS MASTER DRIVE U MT S F/GUFE 93 iz e n o u r s y n c h r o n o u s w in c h s y s t e m l a y o u t 225 drive units, each of which can simultaneously feed up to six hoist motors and keep their collective movements synchronized no matter how the load may vary from hoist to hoist. The master drive units are located in a sound isolated room in the basement because of the high random noise level that is emitted. The original control console contained a patch panel from which the hoist motors could be connected, in group ings of up to six units each, to any of twenty-two pre-set groupings, which in turn, could be switched to either of the two master drive unit control stations. Each control station had an up-down switch, a five position speed switch, a position indicator, and a run-stop switch. University of California at Los Angeles Digital Control System The new University of California at Los Angeles Digi tal Control System (Figure 94) represents one of the first applications of computer sys tems to theatre scenery control utilizing digital technology and computer memory to monitor the location and control the movement of lighting instruments and scenery. This new control module allows groupings of up to six spot- lines to be moved to any desired trim height and their positions recorded into a memory bank and assigned indi vidual pre-set cue numbers. After that, whenever the respective cue numbers are punched into a keyboard and then a "go" cue button pressed, the associated spot-line hoists 226 227 will be automatically switched into the proper group and moved from their previous positions to their newly assigned trim heights. The University of California at Los Angeles system is still limited to the movement of only two groups of hoists at any one time because it has only two master drive units. This permits some lines to be flown in while others are being flown out, but it does not permit the piling-on of additional movements during a flying operation. The syn chronized movement of the individual hoists within a group also precludes the possibility of intentionally flying different units within that group at different speeds. Additional master drive units could be installed in the system to provide greater flexibility in the sequencing of flying movements, but at a cost of over $15,000 per drive unit, plus installation expenses and the cost of further 17 modifying the control module. A very common difficulty encountered in the operation of many types of electric motor driven equipment is in the area of full-load starting and low speed control. Syn chronous mechanisms are particularly susceptable to this drawback because while the frequency varies with speed, the efficiency varies inversely; which is to say that the starting (zero frequency) and low speed (low frequency) efficiencies are very poor. This condition requires con siderable overpowering of the hoist motors during the 228 starting phase, with a corresponding reduction in incre mental control and system efficiency. The loss with this system is evident in that each twenty-five horsepower master drive unit can only power a total of six one- horsepower hoist units. The hoist units are, in turn, limited to a maximum lifting rate of about three feet per second. Heavier loads must be handled by grouping two or more hoist lines together, with a maximum combined capacity of only 1,800 pounds per master drive unit. This does not compare favorably with the 1,000 pound capacity of each individual batten in the Metromatic Loft System. The limited load capacity of the spot-lines in the Synchronous Winch System offers one serendipitous benefit, however, in that the cables only need to be one-eighth inch in diame ter, which permits their use within sight-lines without being readily observed by the audience. The key design feature of the Synchrous Winch System is that the running speed of the individual synchronous hoist motors in a grouping corresponds exactly with that of their driving alternator, which makes it possible for separate loads of different weights to be lifted exactly in unison. The speed of the synchronous driving alterna tor, however, is dependent upon the operating characteris tics of its induction drive motor and the associated clutching mechanism to which it is connected. Regretably, the drive motors in this system are not intended to operate 229 across a continuously adjustable speed range, and conse quently can only drive the alternators at six fixed speed increments. Also, there is no provision for regulating the rate of acceleration or deceleration of the hoist loads, except by the cumbersome process of manually switching the speed control knob on the panel through its fixed incre ments. The usual procedure of merely pushing the Mgo, T or "stop" buttons subjects the hoist units to the jolt of their full starting or stopping torque. The rapid start and stop characteristics of this sys tem are aggrevated by the necessity of having each mechani cal brake release its grip on its hoist unit just as torque is being applied by the motor so that the cable will not slip down under the freed weight of the load. This aggre- vation is compounded by the audible clicking noise that accompanies the actuation of the brake mechanism. In spite of these limitations the Technical Director of the University of California at Los Angeles Theatre Department maintains that the system adequately satisfies their basic design objections of "accommodating the loads encountered in the rigging of lighting instruments, cables, 18 and accessories." It also allows the scene designer "to suspend scenic units at any location." and permits the 19 execution of changes "rapidly and quietly." Sigma Pac System A third noteworthy approach to electrically powered 230 "spot-line” hoist system design is that which has also been advanced by the Peter Albrecht Corporation. Their design, known as the Sigma Pac System, provides for the power oper ation of individual hoist lines which can be situated at any desired location around the stage gridiron (Figure 95). It is a much more complex arrangement than the basic Izenour concept but it also offers a correspondingly higher level of versatility. The major conceptual difference between the two is that the hoists in the Sigma Pac System are driven by independently operating variable speed AC induction motors rather than by permanently "slaved” syn chronous motors as in the Izenour system. This arrangement permits the simulataneous movement of several hoist units with them each traveling at different speeds and moving different distances. The synchronized hoisting function is accomplished through the use of a separate electronic feedback speed control device that is plugged into the system for this particular operation. Some of the pilot Sigma Pac installations, such as the one at the California Institute of the Arts in Valen cia, California, utilize a hoisting arrangement whereby the hoisting units have to be physically moved about on the grid to the desired lifting location and then their lines dropped straight down from the bottom of the hoist unit. This arrangement has proved to be relatively unsatisfactory because the units are very cumbersome and difficult to move 231 232 PATCH PANEL PO W ER . A M D CONTROL C H A N U E I CON SOLE FIGURE 95 5/6M A PAC S VS TPM LA YOUT MASTER- (*l)£ SL/Jl/ET (S) W I N C H E S MANUAL WINCHES 20 about. Also, from the noise standpoint, it was found that the grid itself acts as a resonator and amplifies whatever small noises that are emitted by the hoist units even though they are heavily sound insulated and vibration 21 isolated. Subsequent installations, such as at the State University of New York at Purchase, New York (SUNYP) have the winch units mounted along the base of the railing on the third gallery level with an arrangement of moveable sheaves to direct their cables to the desired hoisting locations on the grid. The installation at SUNYP consists of the following basic components: Nine variable speed winches One control console (including nine individual control modules and one mastercontrol module) Four master-slave synchronizer boxes One receptacle box One circuit breaker panel One plug-in wireway One floor-block mounting rail Nine movable floor blocks Nine movable swivel headblocks Nine movable muleblocks Nine movable swivel loftblocks One winch dolly A complete set of interconnecting cables and miscellaneous h a r d w a r e ^ The winch units, which can each lift up to three hundred pounds at speeds up to five feet per second, are mounted in individual, vibration isolated enclosures. Inside each enclosure is an electric drive motor, an electrically operated mechanical brake, a gear reducer, a cable drum wound with one hundred feet of hoisting cable, 233 an electronic drive unit, and the associated control and logic circuitry to operate the nechanism. A slack cable switch is also included which prohibits the hoist, or group of hoists in a multiple lift operation, from functioning unless the hoist lines are taut. This provides some insurance against cable tangles and damage from a moving load running afoul of other hanging elements. In this regard, each cable is fitted with a lead weight on its free end which permits the hoist to be operated when it has no load attached. A manually adjusted "grid-floor rotary limit switch" is incorporated into the travel mea suring mechanism in the hoist to prevent overtravel of the units being lifted. In addition, a secondary upper safety limit switch is included at each loft block to prohibit a load from accidentally being flown into the grid in case the primary limit switch circuit should malfunction or not be properly set. Power for the hoist units (208 v, 3 phase, 60 Hz) comes from ten individual circuits which originate in a switchboard room on the lower level of the building, pass through a circuit breaker panel in the control room on the first gallery level, and terminate at a plug-in wireway on the winch gallery. A separate set of nine terminals is included in the plug-in wireway for the control circuitry of the hoist units. These control circuits feed into the hoist control console in the control room. Operation of 234 the hoist units from the winch gallery is accomplished by plugging them into the power circuits in the wireway and working the controls on the "at winch" panel attached to each winch unit. Operation from the winch gallery is usually required during the set-up phase to insure that the limit switches are properly set and that the various ser vice connections are plugged in. Operation from the control room is made possible by patching the control cables from the hoist units into the desired control circuit terminals in the wireway and similarly plugging the desired control module cables into the respective control circuit receptacle box on the wall of the control booth. Operation of individual hoist units from the main control console is interrupted, however, whenever any of its associated limit switches, system pro tection devices, or the mechanical brake are inadvertently activated, and requires a trip to the grid to reconnect the service. This "self-chastising" feature is justified on the grounds that "in making the operator climb several flights of stairs from the control booth to the winch gal lery as a penalty for unskilled set-up or operational tech- 23 niques will undoubtedly hasten his learning process." No mention is made of the time lost from such a journey during crucial production shifts, particularly in cases of minor system malfunctions. The main control console contains nine individual 235 control modules, one master control module, and a group of main console controls which include the power on-off key switch, the emergency stop "panic" button, and various indicator lights. The individual control modules each contain a pre-set position dial and a "goM pushbutton for "X" and "Y" oper ating sequences. The pre-set dials are adjustable to indi cate any desired trim position between the extremes of the floor and the grid, within the settings of the travel limit switches. Pressing the MXf T go button causes the associated hoist load to move from its present position, wherever it may be, to the position indicated on the nX, T pre-set dial. Pressing the "Y" button similarly moves the load from its present position (usually the previous "X" pre-set posi tion) to the new nY" pre-set position. The pre-set dials are calibrated from zero to one hundred feet in one-tenth foot increments and have a "push-to-lockM feature to pre vent their unintentional movement. Each control module also has a height indicator— up and down motion indicator lights, a speed selector knob, a mode selector switch, and an auto-manual switch which allows the hoist unit to be operated either by the automatic "X"-"Y" buttons or manu ally. In manual operation the automatic controls are deactivated and the motion of the hoist is controlled by a "joy-stick" lever which varies the operating speed, either up or down, in proportion to the distance that the lever is 236 moved from the central, "null" position. The mode selector switch is used to transfer the hoist operation from the individual control module to one of three control positions on the master control module. The master control module has three sets of push buttons and indicator lights which control group operation of the winches. Each control group, red, blue, and amber, has its own set of MX, T and ,TY" go buttons, which operate in a similar manner as the individual control modules. Any of the nine winches can be connected to any of the three groups in the master control module and driven simultane ously by the operation of a single control button. How ever, the speed and travel distance of each unit is still regulated by the controls on the individual control modules. The function of synchronized, or multi-line hoisting is accomplished through the use of a special Master-Slave Winch Synchronizer box. Up to four hoist units can be plugged into this box, with one acting as the master and the others as slaves. The motion of the master hoist unit is electronically compared to that of the slave units through a feedback circuit and the voltage input to the slave drive motors is continuously adjusted to keep their relative positions the same as the master unit, within a very narrow tolerance range. The synchronizer box is plugged into one of the control circuit terminals in the 237 winch gallery wireway and connected to one of the individ ual control modules in the main control panel. The box incorporates a group lockout circuit which prevents console operation of the entire group of hoists if any one of them stops for any reason. Perhaps the major disadvantage of the Sigma Pac Sys tem, at least as demonstrated by the installations at Cal Arts and SUNYP is that it has so few operating hoist lines. The system may be satisfactory for use in modular or thrust stage theatres which are inherently limited in their scenic capabilities, but it would be totally inadequate as the primary hoisting media in professional or proscenium type theatres with substantial flying requirements. Additional hoist units could certainly be added to the system, but at proportionally greater cost and added complexity. As it is, the system is already cumbersome to operate and the set-up effort is considerably greater than most other powered rigging systems in use. A more practical arrangement would be to employ this type of spot-line hoist system in conjunc tion with some sort of pinrail, counterweight, or power 24 driven batten system. Hydrafloat System Probably the most sophisticated hydraulically powered overhead rigging system ever devised is the Hydrafloat Stage Control System. It was conceived by William Cruse and developed in conjunction with Ralph Alswang, a New York 238 theatre consultant. Regrettably, the economics of their enterprise did not favor the development of a working laboratory installation to test the untried elements of the conception. Instead, the original design was directly translated into two "prototype” theatre installations, one at the New Orleans Theatre of Performing Arts and one at the Uris Theatre in New York City. Both installations con sequently suffered from numerous developmental problems, many requiring extensive redesign efforts, some of which were not economically feasible. The New Orleans theatre, being a city owned performing arts facility, managed to find the additional money and time to follow the develop mental phase through to its present operational state. But the Uris Theatre, a privately owned commercial Broadway playhouse, could not afford to expend the required time and capital to set theirs right, and subsequently tore the 25 system out before it even became operational. The original conception of the Hydrafloat System was organized around the use of one central hydraulic power supply which would provide the motive force for all of the fly lines as well as the wagon drive units and the stage lifts, and of having one central control console from which all of the stage movement operations could be worked (Figure 96). Unfortunately, the management of the New Orleans theatre opted for an electrically driven stage lift system, leaving only the wagon drives and the overhead 239 CO NVENTIO NAL BA? t e n G R ID R IG G ING REMOTEL Y LOCATED HYP RAUL fC P O W E R . S u p p l y C A B L E CYLINDER.\ PATCH PANEL -MANIFOLDED ELECTRO - hydraulic SERVO VALVE STAGE LEVEL CONTROL CONSOLE F/GURE 9C c/ie-Le CYL/NDER. F L O O R 7~FAC fC 3 H Y D R -A F L O A T S Y S T E M LA Y O U T rigging system under hydraulic power, and the Uris managers elected to use only the rigging system. The most significant mechanical aspect of the Hydra float System involves the use of a series of ’’cable cylin ders” for the linear actuating mechanisms. These cylinders, which were discussed in the previous chapter, are charac terized by their unusual nylon coated cable "piston rods” which loop around the outside of the cylinder and join at a clevis drive link. There are ninety-six of these cylin ders in the rigging system of the New Orleans installation. They are mounted vertically on six-inch centers along the wall of the fly loft above the right side of the stage, adjacent to the pinrail rigging gallery (Figure 97). This is the same general location that a double purchase counter weight system would normally be mounted in a Tee-shaped stage house where the loft does not extend over the side- stage areas. It is adjacent to the rigging battens and is conveniently removed from the other working areas of the stage. The clevis of each cylinder is mated through a group of conventional double purchase loft blocks to the six support cables which hold each rigging batten. The cylinders have a maximum stroke of twenty-eight feet, eight inches, which translates to a total vertical batten travel of just over fifty-seven feet. A pulse generator is fitted to each cylinder which calibrates the batten travel into one-eighth inch increments. The system is designed to 241 DO to URJ B_ TH E A TR E - C A B L E C Y L IN D E R , in s t a l l a t io n provide a lift capability of one thousand pounds per batten at speeds up to five feet per second. Each actuator has a built-in check valve in the bottom cylinder port which prevents fluid from inadvertently flow ing out of the cylinder, thereby retaining the batten in a fixed position when the system is not pressurized. A relief valve is also incorporated in the line so that the batten load must be driven in the downward direction by pressure being applied from the power supply at a value above the relief valve setting. The "counter-balance” feature "insures the maintenance of the load in a fixed position, regardless of any failures in the fluid sys- + m2 6 tern. " Fluid flow to and from each cable cylinder is regu lated by a Moog four-way electro-mechanical servo valve. These valves provide a flow capacity that can be very finely and accurately regulated from zero to twenty gallons per minute by means of a low voltage, milliamp electrical input. A mechanical override feature is also provided in the valves which permits the cylinders to be manually operated from the rigging gallery. The servo valves are mounted in groups of three to manifolds which are, in turn, connected in groups of two to the large pressure and return lines that eminate from the central power supply (Figure 98). The rigging system is thus divided into banks of six actuators, each with its own ten micron oil filter and 243 244 r r x & FIGURE 93 NE W O R L E A N S T H E A T R E O F PERFOR. MI N6 A RTS - SERVO VALVE MAN/ FOLDS pressure and return shut-off valves that can isolate the group from the rest of the system for maintenance or emergency repairs. All of the ninety-six hydraulic fly lines plus the fifteen similarly operated wagon drive units are powered by a single power supply unit which is located in a fenced- off area outside the back of the theatre (Figure 99). This particular unit was originally a military surplus submarine control system power unit that was acquired for this appli cation because of its reasonable cost and generally suit able operating characteristics. It has two seventy-five horsepower induction motors, each driving two variable dis placement, pressure compensated pumps capable of delivering up to fifty-one gallons of fluid per minute each, at a working pressure of 1500 psi. Only one of the motor-pump units is required to operate the system, however. The other is retained merely as a stand-by unit. Also, during normal operation, when the demand is relatively low, only one of the pumps supplies pressure to the system. The other pump is set at a slightly higher pressure compensa tion value and provides flow only during those brief peri ods when the demand is above the capability of the first pump. An oil cooler which prevents the system from over heating is located adjacent to the power supply. The electrical control wires for all of the hydraulic actuators in the theatre are routed to a patch panel on the 245 N E W OR. L E . A N j$ > T H E A T R E O P P E R F O R M ARTS- right wall of the rear stage area (Figure 100). There are twenty mating patch plugs for the panel, fed via a coaxial cable to the control console, which can be moved about the right off-stage area to maintain suitable visibility of the performing area (Figure 101). The control console contains twenty individual control modules, each of which incorpo rates position and velocity readout scales, high and low trim position indicators, and velocity and deceleration regulating dials (Figure 102). The main control panel is divided into two sets of ten "joy stick" control levers plus two master levers that can group several hoist units under a single control. Remote control provisions are also incorporated so that a few actuators can be operated from a portable, hand-held box elsewhere on stage. Run, stop, bypass, and pressure controls for the power supply are also located on the panel. Setting up for a scenic movement consists of patching the desired actuators into the desired control modules, setting the high and low trim dials to their desired posi tions, and adjusting the desired maximum running velocity and rate of deceleration. Movement of the actuators is accomplished by moving the respective joy sticks either up or down depending upon the desired direction of travel. The units accelerate and move at a rate roughly proportion al to the rate and distance that the levers are moved away from their central null positions. As the units approach 247 F/6UR.E » NEW ORLEANS THE AT RE O F PERFORMING ARTS- HYDRA FLO AT PATCH P A N E L FI6U&E the end of their travel they are automatically slowed and brought to rest within a fraction of an inch of the posi tion indicated on the respective trim indicator. In principle the system very satisfactorily satisfies most of the aforementioned design criteria for an ideal powered hoist system. In practice, however, the system, as represented by the New Orleans and the Uris installations, has been found wanting in several significant areas. The most troublesome operational difficulty encoun tered with both installations occurs in the area of down ward batten drift when the system is standing idle. This is caused primarily by static leakage, either across the cylinder seals, through the counterbalance relief valve, or in the built-in cylinder check valve. An accumulated leakage of one drop per minute from any or all of these sources would cause the associated batten to drift downward 27 about two inches per day. Well designed hydraulic linear actuators tend to leak only a fraction of that amount, if at all, and in practice, most of the units in the system are in the minimal leakage category. Occasion ally, however, a unit will begin to leak an unacceptable amount, enough even to produce a noticeable downward move ment of a hanging scenic unit during a performance. The bulk of leakage in the cable cylinders, as dis cussed in the previous chapter, occurs in the cable seal glands at the ends of the cylinder. Some additional 251 leakage occasionally may occur internally, across the pis ton seal, mostly because of the high wear rate from its abnormally long stroke. The type of counterbalance relief valve used in this system has a good reputation for minimal leakage. In the event that one should begin leaking, it can quickly be removed and replaced by a spare valve. Unfortunately, this is not the case with the built-in, mod ular check valve in the lower port of the cylinder. In most linear actuator installations a leaking modular check valve could easily be unscrewed from the cylinder port manifold and another one screwed in. In this case, how ever, the check valve is located in such a position on the manifold that it cannot be serviced without first removing the entire cylinder assembly from its mounting on the wall 28 of the stage house. This is a very laborious and time consuming process, and consequently is very reluctantly and infrequently undertaken. Another source of batten drift that has plagued both of the Hydrafloat installations is reportedly caused by the electro-mechanical servo valves that direct the flow to and 29 from the actuators. The units that were selected for this system are extremely sensitive, highly sophisticated instruments that can produce minute changes of flow with correspondingly small variations in their electrical con trol current. Unfortunately, the adjustment of the central, null position (zero flow) on this type of unit is very 252 critical and may occasionally shift slightly, allowing a small flow to pass (either in the up or down direction) when the control lever is in the central, "stop" position. The law of parsimony suggests that perhaps a less complex, industrial type of servo valve with a broader "deadband" in the null position could have performed as well in this application, and without such a stiff penalty in hyper sensitivity . Another vexing problem that has plagued the New Orleans installation is that of maintaining uniform lifting 30 rates during a group hoist operation. In this case the downstage battens tend to move more slowly than equally loaded battens farther upstage. This occurs mainly because the system pressure and return lines, which come from the back of the house, are branched-off to the various groups of actuator manifolds in descending order from upstage to downstage. The supply and return pipes do not have a big enough diameter to handle a large flow without producing a pressure drop that affects the flow rates of the individual actuators. Most of this problem could have been resolved by re-routing the branch lines to equalize the pressure drop in the actuator groups. The actuator servo valves also could be programmed through an electronic feedback circuit (similar in concept to the master-slave elements used in the Sigma Pac System) to maintain uniform flow rates regardless of the individual pressure drop to which 253 they might be subjected. This same feedback circuit could also be used to synchronize the movement of unevenly loaded batten, spot-line, and even stage wagon groupings. The Hydrafloat System, from its two "prototype" examples, could hardly be termed an unqualified success. It was plagued from the outset with horrendous developmen tal problems and is still struggling with numerous vestigial 31 operational difficulties. It has also generated con siderable anxiety from a purely economic standpoint. The rate of cost escalation for the two developmental projects nearly rivals some of the popular examples from our modern defense industry, and the numerous time delays have played havoc with the theatres' sacrosanct production schedules. Even the on-going maintenance requirements turned out to be considerably more extensive than was originally ima- • ^ 32 gined. Unfortunately, these faux pas, plus some unsavory com mentary from a few of the system's detractors in the stage business have tended to cast the entire Hydrafloat concept in an undesirable light. Many of the positive attributes of the system have thus been pushed into the shadows by the seemier side of the operation. The fundamental concepts of the Hydrafloat System are very sound in principle, and the basic operational capabilities match or exceed those of its most advanced electrical counterparts in practice. For example, Hydrafloat battens can carry the same loads as 254 those in the Metromatic System, but will raise them about sixty percent faster. It is nearly silent in operation with no distracting noises from the built-in breaking and holding mechanisms. Large loads are easily lifted and smoothly accelerated to their desired running speed, and then just as smoothly slowed and stopped at precisely the desired elevation. Overloading of the battens, either by weighting them too heavily or by fouling them on adjacent hangings merely causes the affected actuating cylinder to stall at the point of overload with no harm done to the system and no troublesome resetting of the actuator mechan isms after the load has been removed. The spring-centered servo valves and the built-in relief and check valves also act to automatically stop and hold a loaded batten in the event of an electrical failure or other system malfunction. In addition, there is no need in this system for extreme travel limiting circuitry because it is automatically goverened by the bottoming of the piston on either end of its stroke. Even from an architectural standpoint the Hydrafloat System is more advantageous than most other forms of stage rigging. With the power supply outside of the theatre and the relatively compact, low voltage control console on the stage floor the only elements of the system that had to be taken into account in the structural design of the house were the actuator mechanisms and their associated plumbing. This hardware is considerably lighter than the massive electric motors that weigh down the grid of the Metromatic System. They are lighter even than a loaded manual counterweight system. This feature permitted the archi tects to design the upper walls of the stage house for lower levels of stress than would normally be required in a theatre of its size. It has even been noted that the long steel actuator assemblies are mounted so as to ’’provide lateral support and stiffening to the entire stage house 4- 4 - ,,33 structure.” In spite of the early demise of the Uris Theatre installation and the developmental agonies of the New Orleans installation, the users are convinced that they have a system than can move scenery better and with less 34 manpower than any other theatre in the country. Art Drapery Studio System An alternate approach to hydraulic rigging that shows great promise in the American theatre is a system developed by Art Drapery Studio of Chicago. Their basic objective was to produce a relatively simple, reliable, and economi cal system that could be easily maintained and safely operated by a single technician.^ They have thus far completed two such installations, one at the University of Virginia and another at the Hull- man Civic Center in Terre Haute, Indiana. Additional 256 installations are being planned at various other theatres and performance facilities around the country. Although the Hullman installation was not done in a conventional ’’theatre” facility it is sufficiently representative of the basic concept to be used in example. The Hullman Civic Center consists essentially of an oval 10,000 seat sports arena, part of which can be cur tained off into a pie-shaped section that forms a 2,500 seat wedge-shaped theatre-of-sorts for more-or-less thea trical events (Figure 103). A ’’stage house” is effected by flying in several sets of legs and a main back curtain (Figure 104). Additional rigging battens are provided for scenic elements. There are twenty-five battens in all, each eighty-five feet long and supported by ten cables through a grid loft-block system. They can raise loads up to 1,500 pounds each through a vertical travel of sixty- four feet at speeds up to about two feet per second. The actuators for this system are ’’off-the-shelf” three inch diameter commercial hydraulic cylinders about ten feet in length. They are mounted against the left wall of the arena, above and behind the last row of seats (Fig ure 105). The required batten travel multiplication is obtained through a compound sheave arrangement similar to that commonly used in European theatres, which is a deriva tive of the tried and true Andrew Brown/Asphelia 36 examples. In this system the upper end of the batten 257 D O U B L S F > U K C H # S £ & 4 7 T B N fc/G G /A JG § 1 258 HR ill llrki'k ■ . ; F/aURE /04 HULLMAN CIVIC CENTE/Z- STA6E S E G M E N T LAYO UT 259 DO 0) o HJJLLMM cm. C £NT£St: HYDRAULIC. ACTUATOR INSTALLATION } ^ cables pass over their respective loft blocks, across toward the stage-left area, where they are secured to the grid (Figure 106). The multiple sheave block pulls the batten in a double purchase arrangement, which is then con nected via a single cable that crosses to the extreme left side of the arena, over another grid block, down and around a sheave that is attached to the piston rod of an actuator cylinder, back up and around the grid block and down again to the actuator sheave, where it is secured. This arrange ment of two Mblock-and-tackle" sets permits a six-to-one travel multiplication with relatively low friction and moderate cable size. Power for the actuators is provided by a series of twelve adjacently located electrically driven 7-1/2 horse power, 230 volt, variable displacement pumping units (Fig ure 107). This installation uses one pumping unit for every three actuators, rather than one large remotely located power supply for all of the units as in most other hydraulic systems. It was done primarily in the name of reliability and simplified plumbing and power distribution, but was probably also influenced by the factors of availa bility, good service history, and relatively moderate price tags. The pumps are 1,500 psi variable displacement units that feed the actuators through pilot operated closed- center four-way valves that are mounted on the pumping units. Each pumping unit can supply one actuator at a 261 262 r ’ * ■ 2 m t • ' * f ■-* -I /,ff FIGUR.E 106 HUUMM CIVIC CENTER.- BA 263 I F IG U R E 1 0 7 HULLMAN CIV/C CENTER. - HYDPRUL/C POWER SUPPLIES 264 t 9 9 ^ „ A F. ■iff r ' ^m-wmm F l(a U R -£ HULLMflN CIVIC c e n t e r .- time, and is connected to whichever one that is selected by the simple expedient of a pair of hoses with quick- disconnect fittings. The actuators that are not in service remain with their pistons rigidly locked in a fixed posi tion by the fluid trapped behind the disconnect fittings. The use of quick-disconnect fittings obviated the necessity of a complex arrangement of selector valves with their added expense and potential for leakage. The hoses are long enough to reach the actuators normally serviced by the adjacent pumps so that several closely grouped battens can be moved in a simultaneous operation. The four-way valves are controlled from an operating station at the edge of the grid, overlooking the stage area (Figure 108). It consists of a panel with switches for energizing the various pumping units and vertically moving Mjoy-stick" levers for controlling the positions of the four-way valves. The levers function in a manner similar to the ones used in the Hydrafloat and Metromatic systems so that the battens are raised and lowered at a rate approximately in proportion to the distance that the levers are moved away from their central, null position. This system has no provisions for automatically slow ing and stopping the battens, nor any mechanism for setting trim heights except for the extreme up and down limits, which are governed by the bottoming of the pistons in the hydraulic actuators. Also, there are no master controls or 265 other means of grouping several battens together for a syn chronized lift sequence. These features were omitted in the name of simplicity and are justified in this installa tion on the grounds that a moderately intelligent operator can visually control the batten movements from his perch in the loft with greater safety and better accuracy than could several flymen operating a conventional counterweight sys tem from an isolated position on the stage floor. The staging demands of this facility are also relatively simple, and usually do not require the services of more than one operator, or more complex scene shifting equip ment . The designers of the installation have achieved a good balance between keeping costs down and providing a rigging system that meets the particular requirements of the Hull- man Center. The initial cost was within the limits set by the planners of the facility for a powered system and probably less than for an electrical winch system of com- 37 parable capacity and function. Most of the components in the system are made up of standardized commercial units that are readily available, reasonably priced, and noted for their long service life. The installation layout is simple and straightforward. There is a minimal amount of plumbing, valves, and other hydraulic distribution elements to leak or be serviced. The actuating cylinders have a piston stroke that is short 266 enough to assure a reasonably good service life of the pis ton and rod seals and to minimize their attendant leakage. Even the layout of the actuators, with their piston rods retracted in the normally raised batten position, helps to keep the rods clean and lubricated, further reducing seal wear and external leakage. The pneumatically controlled four-way actuator control valves are much cheaper and less complex than the electro-mechanical servo valves used in the Hydrafloat System. They do not meter fluid flow nearly as accurately, but their precision is more than adequate for stage use and they are much less sensitive to contami nation and temperature variations. Being mounted on the pumping units rather than at the actuators enhances their accessibility and also reduces the plumbing requirements. The individual pumping units are integrated power supplies, each with its own drive motor, pump, reservoir, filters, and valves, all mounted on a platform so that the whole assembly can be removed and replaced as a unit in the event of a serious malfunction or for major servicing. If a pumping unit should malfunction during a production, one of the adjacent units could quickly be plugged into its batten actuator to maintain service. Having a separate pumping unit for each actuator in service insures that they will all receive the maximum flow capability of the pumps. This feature might be considered a luxury, however, because all of the actuators seldom 267 require full flow capabilities at the same time. Fewer pumping units of a larger capacity feeding more than one actuator each would have provided a greater range of actua tors that could be used in any single flying operation. They also probably would be cheaper than having so many individual units, except that it also would have required a more complex fluid distribution arrangement to supply the four-way control valves. The location of the pumping units in the auditorium, next to the actuating cylinders permits the shortest possible hydraulic connections, but it also pays the price in terms of noise. Excessive noise from the pumping units is not a serious problem in this facility because of its immense size and the remoteness of the units from most of the audience. But it would be a major dis traction in conventional theatres, and would require the use of large sound insulating chambers around them or placing the units behind the stage wall in a sound isolated pump room. The Hullman installation has already achieved an enviable reputation for reliability and ease of maintenance 3 8 in the short time that it has been in service. The operation of the system is simple and straightforward and does not require the services of a highly trained technical specialist. An operator merely plugs the power units into the battens that he wants to fly and then switches them on at the control panel and moves the appropriate levers to 268 raise or lower them to whatever position he wants. He is, of course, limited by the lack of automatic control fea tures to monitoring the entire operation visually. He must watch the battens to be sure that they start smoothly and run freely, that they do not foul adjacent elements, and that they stop where they are supposed to. He is also restricted in making simultaneous movements to operating only those control levers that he can reach at one time. More complex shifts require the services of an assistant. In spite of these limitations the control functions are simple enough and the power medium responsive enough that an untrained operator can quickly learn to raise and lower a broad range of loads smoothly, quickly, and safely. He even can achieve greater flexibility and control over many operations than could be had with a manual rigging system or with an automatic system that is restricted to fixed speed, acceleration rates, and terminating positions. He also has the comfort of knowing that when the control valves are in the null position the associated battens will be firmly locked in position and that long term downward drift will be minimal or nearly nonexistent, particularly with those battens whose actuators have been disconnected from the pump units. This simplified "modular" rigging concept with indi vidual pumping units supplying small groups of actuators would be ideally suited to theatres where only a few 269 fly-lines need to be powered, or where limited budgets necessitate the acquisition of a powered system on a piece meal basis. It would be wise, however, to assess thorough ly the production demands that will be imposed on the sys tem, particularly in new theatres, and decide beforehand whether it would be more advisable to use this arrangement or to opt for a central power supply concept with its greater complexity and initial cost, but increased range and flexibility. 270 Notes '''Ham, p. 72. 2 Burris-Meyer and Cole, p. 241. 3 Pugh, p. 4. Many theatres in this country have used the fly loft as a convenient storage space. The Auditorium Theatre, in its heyday, stored enough scenery for seven operas at a time in its ninety-six line fly loft. This is not a wise policy, however, because of the potential fire hazzard. The theatres in Germany are prohibited by their fire laws from hanging anything not required for the par ticular show in rehearsal or in production at the time. 4 "The Winch System in the New Metropolitan Opera," Theatre Design and Technology, 13, May 1968, p. 16. ^"The Winch System," p. 16. ^"The Winch System," p. 16. 7 The criteria was derived mostly from a review of the published design parameters for the Winch System at the Metropolitan Opera House ("The Winch System"), plus dis cussions with some of the designers and users of several other power operated rigging systems, particularly those involved with the UCLA Synchronous Winch System and the New Orleans Theatre of Performing Arts Hydrafloat System. "The Winch System,' P • H 00 9 "The Winch System, ' p. 15 . 10"The Winch System,T p. 14. 1;L,,The Winch System, ' P • 16. 1 9 "The Winch System,T P • 16 . 1 3 "The Winch System, ’ p. 16. 14 Donald H. Swinney, "The Synchronous Winch System of Stage Rigging," United States Institute for Theatre Tech nology, New York, 1962. (Mimeographed.) 271 15 Personal interview with William Crocken, Past Tech nical Director, University of California at Los Angeles, Theatre Arts Department, July 1973. 16 "A Digital Scenery System for the Theatre,” Univer sity of California at Los Angeles, Theatre Arts Department. (Mimeographed.) Describes the new UCLA Synchronous Winch control system. 17 "Digital Scenery System.” 18 "Digital Scenery System.” 19 "Digital Scenery System.” 20 Personal interview with Alan Blacher, Performance Coordinator, California Institute of the Arts, Valencia, California, August 1973. 21 The manufacturer has since packaged the hoist units in larger enclosures, with more insulating material. The problem of grid resonance was also found to be a major problem in the writer’s Master's thesis experiments with a hydraulic spot-line hoist system. 22 "Sigma Pac System at State University of New York at Purchase, New York,” Peter Albrecht Corp., Milwaukee, p. 1. (Mimeographed.) Paper describing the Sigma Pac System at the University of New York at Purchase. 23 "Sigma Pac System," p. 1. ^Swinney, p. 3. 25 The writer had a personal demonstration of the hy draulic rigging system at the Uris Theatre a few months before it was discontinued. It was essentially functional at that time, but suffered from some major leakage problems and excessive batten drift that was supposedly caused by servo valves which were not properly centered. 26 Cruse, "hydraulic Rigging," p. 40. 27 The batten travel due to leakage is calculated from the accumulated volume of the lost fluid per day divided by the area of the cylinder less that of the cable, times two to account for the double purchase rigging. 2 8 Personal observation by the writer of the Uris and New Orleans installations, and verified by Joe Laycono, Maintenance Engineer, New Orleans Theatre of Performing 272 Arts, in a personal interview, New Orleans, January 1974. 29 Laycano. 30 Personal observation by the writer, verified by Laycono. 31 DeCuir, Laycano, Cruse, and random statements by various stage personnel at the New Orleans and Uris Theatres. 32 Laycano. 33 Cruse, ’’Hydraulic Rigging," p. 39. 34 _ . DeCuir. 35 Personal interview with David C. Kratzer, Operating Engineer, Hullman Civic Theatre, Terre Haute, Indiana, March 1976. 36 This is a logical arrangement for stage rigging and has become commonly used as a means for increasing batten travel. 37,, , Kratzer. o o Kratzer. 273 CHAPTER VI PROPOSED FLUID POWERED THEATRE FACILITY One of the most important benefits of this study is the opportunity it affords for envisioning potential improve ments in much of the stage equipment now in use. Elements from the various systems that have been studied can be con- jecturally combined to produce new configurations which would emphasize the most desirable elements of each while minimizing their individual drawbacks. The difficulty here is that there are so many possibilities for improvement and such a wide variety of available combinations that they all could not be adequately contemplated within the scope of the study. In addition, the very nature of the theatre dic tates that each new facility be an entity unto itself and, as such, must generate its own unique set of staging requirements and corresponding array of equipment. A rea sonable compromise to this dilema is to entertain one potentially ’’optimum" fluid powered theatre facility that incorporates the better features of most of the systems that were examined in the study. Theatre planners may then contemplate the merits of those elements that could relate to their own installations and discard the rest. This hypothetical design (Figure 109) is aimed at 274 ■REMOTELY LOCATED HYDPAUL/C POUYEP SUPPLY -DOUBLE PUPCEASE HYPEAUL/C BA7TEA/PR/YECYL/NOEPS -f/Y D P A U U C SERVO VALVES M W PU/CR-D/SCOEA/EC T HO SE C O U P L /A /6S ( 3 L-Y L!/Y D E E S PE/S. S E P V O ) -DO UBLE PURCHASE BATTEN P i EG !N E T E E '’ S p /fp E D S T A G E h o u s e y y y y z z , M P U U fC S T ffiB meoH assembly (AIR. BEARING o r c a s t e re d ) CENTRAL LOW VOLTAGE H Y D R A U LIC POWER. CONTROL CONSOLS FO UR SFG /VJSN T ORCHESTRA P/t/ ap*Dn / THRUST STAGE C /F T - HYDRAULIC ALLY DRIVEN TELESCOPING COLUMN ACTUATION "TABLE LEO " STA6E FOO/A -RA ISED 6Y FORTA3LE HYDRAULIC UNOER-STAGE LIFTS SIDS/REAR STAGE HYDRAULIC CABLE- CYLINDER FLOOR TRACK WAGON DRIVES FIGURE /OS /NTEGB/tTED HYPPAUUCALL Y POWEPED AAECHANVZ.EC> S T A G E S Y S T E M 275 satisfying the requirements of a large professional short- run dramatic house, or serious, professionally oriented educational theatre. The layout probably would not be suited to the needs of large operatic or symphony houses, general educational facilities, or small studio, thrust, or modular theatres. The original cost of the theatre and its equipage would be an important consideration, but it would not be as critical a factor as creating a facility with the maximum operating efficiency, flexibility, and overall utility. The auditorium would have to be large enough so that the box office receipts should be able to pay a reasonable share of the operating expenses, and yet small enough to retain the close, intimate feeling required of a proper dramatic playhouse. It would have to encompass a relative ly wide angle in order to permit a theatre of this capacity while still keeping the audience close enough to be in volved in the dramatic action. A balcony would also be desirable in this respect. This semi-amphitheatre type seating would necessitate a stagehouse with a relatively large proscenium opening to permit an acceptable upstage view to the spectators in the side and overhead seats. A reducing curtain on the order of the Auditorium or Vivian Beaumont Theatres would be used for scaling down the vast visual expanse behind the proscenium during presentational or semi-open stage productions. The staging configuration would be adaptable to permit either conventional proscenium, large apron, or deep thrust types of performances. These variations would be accom plished by means of a four section, tee-shaped, Westmont type cable-driven, telescopic column orchestra lift plat form similar to that at the Meramec Theatre. The three sections comprising the large, segmented apron could be lowered to a sublevel to produce an orchestra pit, or loaded at that level with a bank of seats, as at the Vivian Beaumont Theatre, and raised to auditorium level to produce a proscenium arrangement with a greater seating capacity and no distancing orchestra chasm. The thrust configura tion would be accomplished by lowering the center apron segment as well as the wedge shaped fourth lift section in front of it to the sublevel, off-loading the seats and then raising the two segments back up to stage level or whatever other performing elevations that may be desired. The seats to the sides of the thrust segments could be turned inwards in a manner similar to the Meramec or Loab installations. The stage house would be laid out in the general man ner of a conventional European tee-stage theatre, with the side and rear back-stage areas of approximately the same size as the main-stage area. This would permit the rapid shifting of full scale unit or architectural type settings. For economy sake the side sections might be reduced some what in width, as at the New Orleans Theatre of Performing 277 Arts. This would still allow a full stage-sized wagon to be moved upstage while two half-stage width wagons could be moved on from the sides. Steel or asbestos curtains might also be provided to isolate the off-stage areas from light, sound, and fire hazards. The stage wagons would not be permanent as in most European installations but would be made up from standard sized modules that could be quickly linked together to form various sizes of moveable stage units. The modules could be made to be supported either by wheels or by air bear ings, and would have a tubular steel framework that would give them a relatively low profile and provide a built-in ducting system for the air bearings. When not in use they could be easily moved to one of the off-stage areas or unlinked and stacked on end in a back-stage storage area. The wagons normally would be powered by a dog-in-slot Hydrafloat type cable actuator. A series of slots would run parallel with the curtain line in the side-stage areas and perpendicular with the curtain in the up-stage bay. Random movement of smaller units, either in the main-stage, apron, or thrust areas could be easily accomplished by fitting air bearings, taping over the effected slots and trap seams, and pushing the units by hand. It would be possible to construct a single, large up stage wagon unit as a "rolling way," like the one used at the Hofburg Theatre, which could span most of the lift 278 segments in the central-stage area, and cover the cavity when they are down. A large revolve might also be built into this unit. But, with all of the other means of scene shifting available, this piece of equipment would have to be considered an expensive, superfluous luxury. Even a large, built-in revolve would not be desirable in this facility because the same function could be accomplished with a University of Texas style portable disc. In fact, two or three of these discs, or disc segments could be used to accomplish multiple revolve or jack knife stage func tions, either laid on the stage floor or mounted on the wagon units. Large scale discs could be built up by secur ing segmented concentric rings around a disc unit and con necting their hydraulic drive motor control circuits to that of the disc. Concentric revolve functions could be accomplished by driving them independently of each other. It is problematical whether or not the discs should be supported by air bearings. Weight distribution would be the deciding factor. If air bearings were to be used it would be advantageous to fit them into the disc structure rather than to a framework on the floor as at the Pacific Conservatory of the Arts, because they could then be grouped in concentrated areas to support any uneven load distribution on the disc. Air would be supplied to the disc through a swivel fitting in the disc hub, and to the hub from below-stage through a trap or stage access plug. 279 The entire main-stage area behind the proscenium opening would be divided into a system of elevating trap modules similar in construction to the floor of the modular theatre at the University of Texas. The modules would be smaller than those at the University of Texas, probably on the order of six feet wide by eight feet deep, but would be made with the same arrangement of steel "table legs" that fit into a framework of larger struts extending down into the area beneath the stage. The modules would be elevated, as at the Texas installation, by means of a portable hy draulic lift that is wheeled under the respective modules and raised to lift it to the desired level, and then secured by pins inserted in the legs. Each module in this installation, however, would be divided into smaller trap sections, any or all of which could be serviced by one of the portable lift units to raise or lower performers or set pieces during a production. Temporary "bridge" sections could be assembled by removing a row of modules across the stage, bolting some of the stage wagon modules together over the gap, and then elevating them as a rigid bridge structure with two or three appropriately spaced portable lift units. Tilted or raked stage sections similarly could be assembled by bolting modular stage wagon units together and supporting them with trap modules raised to different heights. Power for all of the hydraulic stage machinery in the 280 theatre would, come from an isolated central power supply located in the basement or outside of the building. The power supply would contain a large reservoir, an accumula tor, an oil cooler, and two large industrial type variable displacement pumping units, either of which would have sufficient capacity to supply the bulk of the staging demands. One of the pumps would be set at a slightly lower operating pressure than the other so that it would deliver fluid to the system only during those brief multiple actua tor operations when the first pump cannot quite keep up with the maximum system demand. These settings could be reversed during their annual maintenance period to extend their service life. Even the Westmont type telescopic column lifts would be driven by hydraulic actuators supplied from the central power supply. They are quieter and would be easier and cheaper to install, operate, and maintain as part of the integrated fluid power system than electric motors would be with their separate power and control requirements. The overhead rigging in this theatre would be pat terned after a composite of the Hydrafloat and Art Drapery Studio systems. The rigging actuator layout would be simi lar to that of the Hullman Civic Theatre, along with their double purchase batten, double purchase cylinder rigging system. Some additional spot-line actuators would be included to supplement the rows of conventional pipe 281 battens. This system could also be fitted with a few manu al counterweight lines, but they would also have to be of a double purchase arrangement because of their location on the upper wall above the side-stage area. They would con sequently be considerably heavier, more expensive, and less efficient than the adjacent hydraulic actuators. The rigging actuators would be supplied by a series of single-stage industrial hydraulic servo valves located adjacent to the bank of actuators. These valves would be connected to the central power supply in a manner similar to the Hydrafloat installations, except that the plumbing would be branched so as to ensure an equal pressure drop at all of the actuators during multiple lift, full flow operations. Since there is a negligible probability that more than a third of the actuators in the rigging system would ever be used in a single production there is no compelling necessity to provide more than one servo valve for every three actuators, as is the case at the Hullman facility. And in like fashion the servo valves would be connected to their respective groups of actuators by means of flexible hoses with quick disconnect type end fittings. In this installation, however, the hoses would be long enough to span several groups of actuators so that several adjacent battens could be connected at the same time. Simple, less expensive motor operated control valves could be 282 incorporated into the servo bank to handle those permanent lighting and curtain pipes that do not require precise speed and position control. The use of quick-disconnect hoses would also eliminate the need for an electrical patch panel near the control station. The control console would be on the stage floor near the stage manager’s station. It would also house the con trols for all of the other pieces of hydraulic stage machinery in the theatre. The integrated control console probably would be the single most costly and complex item in the entire stage machinery package, and as such it should be carefully designed to strike the best balance between reasonable capabilities and reasonable costs. The simple joy-stick manual control system of the Hullman installation would be preferable to the University of Cali fornia at Los Angeles Digital Control System if the demands of the proposed system were simple enough. However, this is not the case. This system could have too many actuators, fed by too many servo valves, operating simultaneously in too many parts of the theatre to be controlled by simple joy-stick levers. On the other hand, a University of Cali fornia at Los Angeles type digital control system probably could be made to handle the operation if such functions as individual variable acceleration and speed control for each actuator, and pile-on multiple actuation features could be programmed into it without making its cost and complexity 283 entirely too exorbitant. Unfortunately, this probably is also not the case. A more reasonable mid-position might be to allow those functions which can be safely, reliably, and effectively handled by one or two trained operators with manual controls to be left to manual control, and make pro visions to program the more complex, multiple actuation operations into some form of semi-automated control mechan ism. This could be done through a variation of the Hydra float control system. Each servo valve would be fed to a module on the control panel which could regulate its actua tor's acceleration rate, maximum speed, and high and low trim. A joy-stick lever would also be provided so that it could be operated individually under manual control. Sev eral similarly equipped master control modules would also be provided, each one designed so that several different servo control modules could be keyed to it and operated as a group. This would permit the operators to control the simpler functions manually and to program the more complex group shifts into a series of manageable joy-stick opera- t ions. In addition to these basic features, such convenience items as a portable, hand-held control box for on-stage visually cued shifts could be easily incorporated in the system. Specialized performance functions such as synchro nizing the movement of a group of battens could be accom plished by feeding their respective position transducer 284 signals into an electronic feedback device similar to the one used in the Sigma Pac System. This mechanism could then adjust the control signals to the malingering servos and bring their flow rates into line with the rest of the actuators in the group. Safety features such as mechanisms to prevent damage from fouling battens could also be pro vided if desired. This could be done by fitting the respective servo valves with pressure regulators, and then adjusting them so that the corresponding actuators could just carry their load. If the load on a batten were then increased by fouling against the hangings on an adjacent batten during a lift, then the lifting actuator would merely stall, holding both battens fixed in that position until the added load is removed, or the fouling batten is lowered. Myriad other ingenious features could be added to the system, depending upon the available budget and the incli nations of the theatre planners and users, but ea,ch new item adds to the expense and complexity of the operation, and eventually the functional benefits of the extra equip ment would be overshadowed by the added expense and work involved in setting it all up and keeping it running. The best approach here, as with most other things, would seem to be to follow the law of parsimony and keep the system a simple as possible, consistent with the need to hold the costs and man-hours down and the utility up. 285 Most of the equipment in this proposed facility was selected with that objective in mind. The central power supply, being a standard industrial item, would be reliable, durable, easy to maintain, and considerably cheaper than powering each piece of equipment individually. Most of the other hydraulic components in the installation also could be selected from standardized, readily available, off-the- shelf industrial stock, and could be made largely inter changeable among the different pieces of stage equipment. The telescopic-column orchestra lift and portable trap lift systems also minimize the need for expensive subgrade structures and elevator equipment and substantially in crease the number of ways in which the stage floor can be arranged. The modular wagon and disc units would be easy to assemble and would provide a wide range of horizontal movement options. The quick-disconnect, servo controlled rigging system probably would be among the simplest and easiest operating powered rigging systems available and yet still would match or exceed most of the performance capa bilities of the most complex and expensive systems now in use. In general, the machinery is designed along the modu lar concept so that the facility could be initially equipped with the minimum number of wagons, discs, trap lifts, rigging servos, control station modules, etc., re quired to make it function and then adding to them at a later date as additional budgets and needs are realized. 286 CHAPTER VII SUMMARY, CONCLUSIONS, AND SUGGESTIONS FOR FURTHER WORK This study was undertaken to provide theatre people with a reasonable basis for appraising the fluid power medium as a means of moving stage equipment. Fluid power mechanisms posses numerous inherent economic and functional advantages over electrically powered equipment, along with a few notable drawbacks, and it is important to examine some of their workings and evaluate their capabilities in relation to comparable electrical equipment. All of the fluid power systems that were studied con tain a power generating device, a controlling mechanism, an actuating device, the fluid medium, and enough pipe, hoses, or manifolding to tie it all together. The pneumatically driven systems obtain their power in the form of air that is compressed and stored in a receiver until it is released into an actuator of air bearing unit. The hydraulic sys tems, which utilize a noncompressible fluid medium, require a pump to energize the fluid as it is being used, except in the cases where a pressure storing accumulator is incorpo rated. The systems are all controlled by some form of valving mechanism, be it a simple one-way check valve, a 287 two-way water faucet type shut-off valve, or a very sophis ticated electro-hydraulic four-way servo-valve which can precisely regulate the flow to an accumulator from a re motely generated electrical control signal. Most of the actuator mechanisms consist of linearly moving rams or cylinders that push or pull directly against a load, or against a block-and-tackle arrangement where longer travel is in order. Hydraulic motors are occasionally used when a rotational movement is desired, such as in turning re volves or disc stages, but their on-stage use is limited because of the noise factor. Probably the first theatre to employ fluid powered was Booth's Theatre in New York, which opened in 1869. It utilized a system of large water powered rams with a rack- and-gear travel multiplying device to raise scenery from below stage. A few years later a Scotish technician named Andrew Brown devised a system for operating all of the stage sinks, bridges, overhead rigging, an on-stage water fall effect, a series of fire hydrants, and a crude audi torium air conditioning system from one isolated steam driven hydraulic power supply. In 1882 an Austrian engi neer named Gewinner designed the Asphelia Safety System, which was used in several major continental theatres. It contained a complex array of hydraulic machinery which raised, lowered, and tilted a stage full of bridges and sinks, and remotely powered a complete fly system with 288 actuators located in the basement. The best American counterpart to these systems can be found at the Auditorium Theatre in Chicago, which opened in 1889, and is still in existence. This theatre has five hydraulically operated stage-width bridges with smaller hydraulic lifts inside of them. In addition, it has two small hydraulic "Faust traps" and five large horizontal rams which raise a five ton reducing curtain, the main curtain, the fire curtain, and two paint frames. By the turn of the century electric motors and large scale generating plants had been developed to the point where they had become easier to install and cheaper to operate than the larger, more cumbersome water driven hydraulic machinery of the time. Consequently, the use of hydraulically driven stage equipment generally declined to the point of operating orchestra and stage lifts. Very few large scenically oriented theatres were constructed during the first half of this century, and most of them either used electrically driven equipment (except for the stage lifts) or merely reverted to manual operation for the flys and wagons. However, since World War II, fluid power tech nology has made great advancements and much of the new equipment is finding its way into all types of theatre applications from huge fully equipped operatic houses to small scale experimental facilities. Compact, powerful hydraulic motors are being used to rotate portable disc 289 stages. Pneumatic actuators and self-contained, portable hydraulic lift units are used to vertically position seat ing and stage segments in adaptable and modular theatre installations. Hydraulic scissors lifts and telescoping cylinder systems are also proving to be an effective means of elevating stage and orchestra segments. Even conven tional stage and orchestra lift systems have been signifi cantly improved with the development of better hydraulic seals, fluid medium, pumping components, and control cir cuitry. The introduction of air bearing technology has opened new avenues in the movement of stage wagons and discs that were not feasible with conventional wheeled or castered units. The relative silence, low friction level, and great load carrying capacity of air bearings have allowed the use of much larger, heavier unit set pieces in open stage applications. Perhaps the greatest improvements in powered stage movement have occurred in the area of powered rigging sys tems. One such system utilizes a series of unique hydrau lic cable-cylinder actuators to power a full array of rigging battens, in addition to fifteen floor track clevis drives for moving large wagon units. Each of these cylin ders is controlled by an electro-hydraulic servo-valve— an aerospace development that permits the precise metering of fluid in proportion to slight variations in an electrical control current. This current is fed, via a patch panel, 290 from an on-stage control console. One operator at the con sole can simultaneously control the acceleration, running speed, and stopping positions of up to twenty actuators with considerable ease and accuracy. The entire system is fed from a single remotely located power supply. A much simpler, less expensive system operates through a small bank of pilot operated hydraulic servo valves, which are patched by quick disconnect hose fittings into a bank of hydraulic cylinders with pulley-block arrangements not unlike those in the century old Andrew Brown system. There are only one third as many valves as cylinders for economy sake because less than a third of the rigging battens would ever be in use at the same time. The servo valves are effectively operated from a simple ,Tjoy-stickn lever con trol station which is also reminiscent of the tried and true control levers so successfully used in the vintage installations. Most of the fluid powered stage equipment examined in the study has been demonstrated to operate more accurately, quietly, quickly, smoothly, and with heavier load capaci ties than comparable electrically powered equipment. In addition, it has generally been found to be lighter, simpler, more compact, less costly, and inherently safer than its electrical counterparts. But on the other side, some of it has been plagued with problems of leakage, noise, high maintenance, and poor design. Also, much of the new 291 equipment is still very much in the formative stages of development and will require considerably more experimenta tion and use before it can be deemed suitable for general service in the theatre. None-the-less, it still offers great promise for substantial improvements in the overall flexibility, efficiency, economy, and reliability of power operated stage equipment. Yet, in spite of its successful historical background and demonstrated present day capabilities, fluid power still is considered by most theatre planners and users as a medium only suited for driving stage lifts. Consequently, there is still much to be done before the medium can be considered as a major element in modern day stage tech nology . Stage technicians, equipment designers and theatre planners need to become more familiar with the mechanics of fluid power and with the work that is being done with it in the theatre. This is no easy task because familiarity breeds on itself, and there are so few familiar people in the business to spread the concept to the rest, and so little equipment in service, in such insulated installa tions, that most stage practitioners have no opportunity to see it in operation so that they can learn for themselves. The most practical remedy for this is for those users and conceivers who are true believers in its capabilities to boast more about their fine equipment, and for the 292 manufacturers with a vested interest in seeing its use grow, such as, Art Drapery Studio, to more actively market their hydraulic wares in such traditional forums as tech nical theatre journals, theatre convention product display booths, and by hiring knowledgeable theatre engineering representatives to make more individual contacts. Much of the fluid power work that is now being done in the theatre is so tentative and exploratory in nature that it could not yet be offered as fully conceived, properly developed merchandise. Therefore, much more experimenta tion and developmental work needs to be done on all levels, from simple shop-built portable lifts and air bearing modules to full scale powered staging systems, in order to bring the overall state-of-the-craft up to acceptably safe, functional and reliable levels. And the results of this work needs to be published, or otherwise made available to the technical theatre community. Knowledge of related industrial applications and methods of design, construction and operation also need to be made more generally avail able. In addition, information needs to be gathered from a cross section of power equipped theatres on the frequency of use and actual conditions under which this equipment is being used so that prospective purchasers of new equipment can better project in what way theirs probably would be used, and whether or not its probable use would justify the expenditure. 293 These informational aspects could best be accomplished through the work of interested manufacturers, educational institutions, or technical theatre organizations such as the United States Institute for Theatre Technology. These bodies should also be encouraged to establish a system whereby the expected performance criteria of the various types of equipment could be better delineated and, where possible, codified, or at least clearly set down so that prospective users and manufacturers would have a clearer idea what each other has in mind in a proposed installa- t ion. Prototypes of new systems or newly developed pieces of equipment definitely should be tested in a laboratory or small experimental installation before being unleashed on a working theatre facility. And before new equipment is accepted by a theatre it should be measured by test against the specified operating parameters, and the results of its demonstrated capabilities made available to the technical theatre community so that they can properly weigh and judge it in relation to other similar types of equipment. Next to human muscle, fluid power is the oldest medium for driving stage machinery. But it has been largely passed over in the march of electrical technology. And it needs to be seriously reconsidered as a competitive alter native, because power operated stage equipment is usually very expensive, requires considerable developmental effort, 294 and has a high degree of permanence once it has been put into service. And it is important to proselytize the kinds of machinery that best combine the virtues of flexibility, efficiency and economy. This study has attempted to do that. 295 WORKS CONSULTED 296 WORKS CONSULTED Books Blaine, Robert Gordon. Hydraulic Machinery. London: E. and F. N. Spon, Ltd., 1897. Brown, T. Allston. A History of the New York Stage. New York: Benjamin Blom, Inc., 1903. Burris-Meyer, Harold, and Edward C. Cole. Theatres and Auditoriums. New York: Reinhold Publishing Corp., 1964. Clark, Norman. The Mighty Hippodrome. New York: A. S. Barnes and Company, 1968. Downing, Samuel. Elements of Practical Hydraulics. London: Longmans, Green and Company, 1875. Granville, Wilfred. The Theatre Dictionary. New York: Philosophical Library, 1952. Ham, Roderick, ed. Theatre Planning. London: The Archi tectural Press, 1972. Hartnoll, Phyllis. The Oxford Companion to the Theatre. 3rd ed. London: Oxford University Press, 1967. Hedges, Charles S. Industrial Fluid Power. Dallas: Womack Machine Supply Company, 1968. Henke, Russell W. Introduction to Fluid Power Circuits and Systems. Reading, Massachusetts: Addison-Wesley Publishing Company, 1970. Hudson, Kenneth. Industrial Archeology, An Introduction. London: John Baker Publishers, Ltd., 1963. Keller, George R. Hydraulic Systems Analysis. Cleveland: Industrial Publishing Company, 1969. Lewis, Earnest E., and Hansjoerg Stern. Design of Hydrau lic Control Systems. New York: McGraw-Hill Book Company, 1962. 297 Mielziner, Jo. The Shapes of Our Theatre. New York: Clarkson N. Potter, Inc., 1970. -----------, ed. Theatre Check List. Middletown, Connecti- cutt: Wesleyan University Press, 1969. Nevins, Allen, and M. H. Thomas, eds. The Diary of George Templeton Strong. New York: The Macmillan Company, 1952. Rogers, William. Pumps and Hydraulics. New York: Theo. Audel and Company, 1905. Rouse, Hunter, and Simon Ince. History of Hydraulics. Ames: State University of Iowa, 1957. Sachs, Edwin 0. Modern Opera Houses and Theatres. London: Benjamin Blom, Inc., 1896. Schubert, Hannelore. Moderner Theaterbau. Stuttgart: Karl Kramer Verlag, 1971. Vardac, Nicholas. Stage to Screen. New York: Benjamin Blom, 1949. Wilson, Aubrey. London's Industrial Heritage. New York: Augustus M. Kelley Publishers, 1968. Yeaple, Franklin D., ed. Hydraulic and Pneumatic Power Control. New York: McGraw-Hill Book Company, 1966. Other Works "Air Bearing Catalog." Airfloat Corp., Santa Barbara. Brown, Andrew Betts. "Hydraulic Machinery for Actuating Stage Effects." British Patent No. 3593, 1875. Bunce, 0. B. "Behind, Below, and Above the Scenes." Appleton's Journal of Literature, Science and Art, 3, No. 61 (1870), 589-597. Calhoun, Lucia Gilbert. "Edwin Booth." The Galaxie, Jan. 1869, pp. 86-91. Cruse, William. "Hydraulic Rigging." Theatre Crafts, 4, No. 2 (1970), 20-24. Davis, Pete. "Upside Down Airbearings." Theatre Crafts, 10, No. 2 (March-April, 1976), 64. 298 "A Digital Scenery System for the Theatre." University of California at Los Angeles, Theatre Arts Department. (Mimeographed.) "Dover Levelator Lift." Information pamphlet. Publication IE-050. Dover Corp., Memphis, 1973. Fisher, Jules. "The Modular Theatre, Some Random Notes on the Design." Information paper. California Insti tute of the Arts, Valencia, California. Helgesen, Terry. "The Hollywood Pantages." Theatre His torical Society Publication, A-l, 1973. "The New York Hippodrome." Scientific American, 92, No. 12 (1905), 139-142. "100 Jahre Stahl im Theaterbau." Stahlkonstrukionen im Theaterbau, pp. 3-4. Pugh, Jonathan. "Restoring the Auditorium." Talmanac. Chicago: Talman Federal Savings and Loan Association, 1964. "Rotary Levelator Lift." Information pamphlet. Publica tion RE-195-C. Dover Corporation, Memphis. Sherwood, Benson. "Stage Plans, Booth’s Theatre." In "Edwin Booth, Producer— A Study of Four Productions at Booth's Theatre." By Gerald Honaker. Diss. Indiana University 1969, p. 116. "Sigma Pac System at State University of New York at Pur chase, New York." Peter Albrecht Corp., Milwaukee. (Mimeographed.) Soot, Olaf. "Engineering Concepts in Stage Equipment." Theatre Design and Technology, 6 (October 1966), 12- 14. Swinney, Donald H. "The Synchronous Winch System of Stage Rigging." United States Institute for Theatre Tech nology, New York, 1962. (Mimeographed.) Vickers Mobile Hydraulics Manual M-2990-S. Troy, Michigan: Sperry Rand Corp., 1967. Vickers Industrial Hydraulics Manual 935100-A. Troy, Michigan: Sperry Rand Corp., 1970. 299 "The Winch System in the New Metropolitan Opera." Theatre Design and Technology, 13 (May 1968), 15-19. Personal Interviews Bell, William D. Sales Engineer, Dover Elevator Company, Los Angeles Office, August 1974. Blacher, Alan. Performance Coordinator, California Insti tute of the Arts, Valencia, California, August 1973. Crocken, William. Past Technical Director, University of California at Los Angeles, Theatre Arts Department, July 1973. Cruse, William. Designer of the Hydrafloat System, Los Angeles, August 1973. Curtis, Robert. Associate Director of Facilities, Califor nia Institute of the Arts, Valencia, California, February 1974. DeCuir, R. J. Theatre Electrician, New Orleans Theatre of Performing Arts, January 1974. Fasnacht, Monty. House Manager, Auditorium Theatre, Chi cago, July 1974. Gerba, George. Technical Director, Walnut Street Theatre, Philadelphia, July 1973. Grosser, Helmut. Technical Director, Cologn Municiple Theatre, Cologn, Germany, September 1975. Hektner, William. Technical Director, San Diego State University, Theatre Department, February 1976. Howard, George C. Theatre Design Consultant, February 1976 . Huntoon, Walter. Technical Director, Golden West College Theatre, Huntington Beach, California, November 1975. Jackel, John. Theatre Manager, Meramec Community College, St. Louis, March 1976. Kobus, Fred. Head Theatre Technician, California State University at Long Beach, Theatre Arts Department, January 1976. Kuntner, Rudolph. Stage Manager, Metropolitan Opera House, New York City, April 1974. 300 Kratzer, David C. Operating Engineer, Hullman Civic Theatre, Terre Haute, Indiana, March 1976. Kuntner, Rudolph. Stage Manager, Metropolitan Opera House, New York City, April 1974. Laycano, Joe. Maintenance Engineer, New Orleans Theatre of Performing Arts, New Orleans, January 1974. Loeb Drama enter, Cambridge, Massachusetts, August 1974. Peluso, Dion. Theatre Manager, Fox Theatre, St. Louis, August 5, 1973. Philpot, Jack. Stage Electrician, War Memorial Opera House, San Francisco, March 24, 1975. Rothgeb, John. Designer, University of Texas, Austin, Theatre Department, December 1973. Schmitz, Lodovicus. Assistant Technical Director, Hesse State Theatre, Weisbaden, Germany, September 1975. Soot, Olaf. Theatre Engineering Consultant. Designer of the California Institute of the Arts modular theatre lift system, April 1974. Tidwell, Richard. Technical Director, Tyron Guthrie Theatre, Minneapolis, August 1973. University of Utah, Theatre Arts Department, March 1976. Westmont Industries, Santa Fe Springs, California, February 1973. 301

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