Design, Manufacture and Installation of Theatrical Equipment Worldwide

Technology Aiding Art

Whether one is designing a high school auditorium or a major cultural arts center, new performance spaces require rigging systems that will allow the equipment onstage to be raised and lowered.

It is essential end-users of the theater—stagehands, electricians, set and lighting designers, and facility managers—have the ability to move scenery, lights, speakers, curtains, and other stage equipment to meet the requirements of individual productions, as well as for maintenance and cleaning of essential systems.

for many theaters, the rigging equipment’s primary use is vertically moving scenery smoothly and simply. this is sometimes accomplished in full view of the audience for added dramatic effect.

The theater requires curtains that mask equipment from audience view. the height of this drapery must change to meet the requirements of specific productions. many facilities have a house curtain that raises or lowers at the beginning and end of the performance, and building codes also require theaters to have fire curtains to shield the audience and/or actors from a sudden blaze. all these elements need rigging to properly function.

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Every play, concert, musical, dance company, lecture, or call to worship is different, and the theater in which these events take place must be versatile enough to accommodate multiple uses. to determine the number of rigging line sets needed, it is important to know all intended uses of the stage.

If the stage will have multiple uses, it is best to err on the side of abundance when it comes time to specify the rigging. for example, a middle school may only have a few sets to allow the lighting equipment to be raised and lowered for maintenance. a high school with an active drama program could have 20 to 40, while a college could require more. professional theaters can have 60 to 100 sets, especially if they host touring broadway shows.

Types of rigging

In the simplest rigging setup, battens (pipes) or tracks are dead-hung (i.e. static-mounted) at a fixed height from the ceiling to support curtains, lights, or scenery. this scenario may be necessary when the stage has a low ceiling, or if the client’s funds are limited. since the curtains or lights cannot be raised or lowered, all maintenance changes require the use of a ladder— an inconvenience at best, and a hazard in the wrong hands.

While this could be an acceptable approach for a middle school, any stage used for presentations or lectures needs a few sets that can be utilized to raise and lower banners, signs, and projection screens, or to support hanging microphones.

The most common form of rigging over the last century is counterweight rigging, a manually operated system employed in schools and professional theaters since the early 1900s. before counterweights, raising and lowering scenery took many

strong men—usually sailors—to pull the heavy loads up or carefully lower them into position. (sandbags eventually aided this process.) the physics of counterweight rigging are deceptively simple: the load being raised or lowered— scenery, curtains, or lights—is counterbalanced by an arbor loaded with weights (usually steel, as the material is more cost-effective than cast iron) at roughly the same heaviness as the load over the stage (figure 1).

Economical to purchase and install, manually operated counterweight sets offer versatile performance capabilities, allowing skilled operators to raise and lower several drops and set pieces simultaneously at varying speeds, with one person for each moving line set.

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however, when counterweight rigging is specified, it is important to emphasize to the client all operators must be trained by a certified professional expert in proper use, especially if amateurs or students will be running the system. the loads on sets will differ as the suspended scenery and equipment are changed, demanding the user adjust the counterweight accordingly. a trained operator can feel any change in the load or contact with an obstruction and take corrective action.

For new installations, automated (i.e. motorized) rigging has gained considerable popularity as the technology becomes more affordable and accessible to middle and high schools, colleges, and churches. professional theaters usually choose automated rigging for safety, versatility, and the ability to set cues in which multiple sets can move at once. once these are set, the rigging moves scenery in exactly the same sequence and at the same speed every time, creating dependable scene changes for every performance that look exactly as the set designer and director determined they should.

while operators still require training to use the system, motorized sets are easier to use than

counterweight ones, because they do not require the handling of steel weights or a command of the physics of counterbalance. operators move the sets using one of many control system options, from simple up/down push button panels to sophisticated computerized systems with three-dimensional displays and the ability to record and play back cues.

Motorized rigging requires less backstage space and less structural steel than counterweight sets, making an automated system an economical choice over the long run, although the initial cost is higher than comparable counterweight sets.

How to choose the right automated hoists

Motorized hoists are available in a tremendous range of speeds, capacities, types, and costs. it is best to consult a professional in the industry to determine exactly which ones are needed for the installation.

Fixed vs. variable speed

Fixed speed hoists are generally used for heavy loads that do not have to move dynamically in front of an audience. these are often the best choice for lighting battens, speaker clusters, and orchestra shell ceilings.

Variable hoists offer an extensive range of speeds, making them ideal for moving scenery. a hoist that performs a subtle move at a rate of less than 0.01 m/sec (1 foot per minute [fpm]) can suddenly travel at more than 0.5 m/sec (100 fpm) in the next cue, creating a dramatic effect in front of the audience. scenery sets in college or regional theaters typically run at maximum speeds of 0.6 to 0.9 m/sec (120 to 180 fpm), while major performing arts centers may need the ability to move at 1.2 m/sec (240 fpm). curtain hoists for the grand drape can run even faster.

Variable speed hoists require solid-state vector drivers rated for hoisting duty, with the reliability of safety features necessary for use in a theatrical environment. the best high-speed hoists are constructed with dynamic braking systems, which decrease the potential for runaway sets and onstage accidents.

In most cases, the gear motor lifts the load directly, so there is an overhauling load. basic variable frequency drives (Vfds) do not deal well with these loads, as they produce low torque at low speeds, making it difficult to decelerate. more sophisticated drives—such as closed loop vector drives—provide dynamic braking, electronically controlling a descending load.

Weight capacities

in addition to speed, it is important to understand the theater’s need for each set’s weight capacity. scenery sets are typically

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rated to carry 20 to 35 kg/m (15 to 25 lb/ft) of batten length, while lighting sets are rated higher, at 35 to 45 kg/m (25 to 30 lb/ft). these capacities increase for major professional theaters and opera houses. for sets with large fixed loads of a few thousand pounds, motorized hoists can be assisted with counterweight hoists to reduce the weight of the load on a single hoist.

Compact hoists may be built economically using ‘moving drum’ technology, making motorized rigging affordable in facilities where it may not have been previously considered. in this type of hoist, the drum moves so the point at which the wire roll leaves it is always aligned with the head block. this allows the head block to be next to the drum, forming a compact, self- contained hoist. the hoists are manufactured in standard speeds and capacities, selected to fulfill the needs of K−12, college, and regional theaters.

High-capacity fixed-speed hoists are used for lighting, shell ceilings, and other utility sets that are stationary during a performance. Variable speed sets are used for scenery, curtains, and other elements that move for dramatic effect during a show.

While standard off-the-shelf hoists can handle most routine theatrical productions, some unusual applications require custom equipment. examples include:

  • acoustic banners;
  • moving ceilings;
  • orchestra shells;
  • chandeliers; and
  • other structural lifting or movement.

Designed and built to meet the unique specifications of particular rigging challenges, they can include capacities in excess of 45,000 kg (100,000 lb) and may be capable of higher speeds than standard hoists.

Choosing the right control system

With a wide selection of control systems available—from simple push button operation to computerized consoles—it can be hard to know which one makes the most sense for the project. control systems can be as basic as a module for a single hoist with up to four user-designed presets, or as sophisticated as a wall-mounted or pedestal control display with three-dimensional graphic representations of the line sets and scenery hanging from each.

Costs for these systems are as varied as the options themselves. a small assembly with a few fixed speed hoists may range in tens of thousands of dollars, while a complex system for an opera house can run well into the millions. the theater consultant and rigging supplier can work with the design team to determine the most appropriate configuration for a project, based on the versatility required and the budget given.

It is critical to specify industrial-grade computers and programmable logic control (plc)—the type of system used to run elevators, assembly lines, and computer numerical-controlled (cnc) machining operations. these dependable systems provide the reliability necessary for overhead lifting.

At the same time, it is important to specify controls actually designed for use in a theater, preferably by people who have a background as stagehands, designers, or technicians in the theater industry. such controls require more than the ability to move several hoists simultaneously at different speeds and to different heights— computerized systems allow operators to make the same complex moves at every performance and have the rigging function exactly as it did the previous night.

Safety is of paramount concern, as injuries can occur if a runaway batten drops thousands

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of pounds on the people below. to guard against this, the control system requires a ‘hold-to-operate’ button to ensure the operator is at the console during movement onstage, so he or she can react quickly if an obstruction appears below a moving batten. a key-operated on/off switch is another good feature. each line set should have two levels of mechanical end-of-limit switches as well as software limits programmed for each movement. load monitoring adds another level of safety.

A handheld remote control device can be a valuable tool, but if a wireless system is selected, it should have the proper safeguards to screen out signal interference. surprisingly, few regulations exist for theatrical equipment, so some lower- cost suppliers provide control systems that operate using simple wifi—this does not provide the necessary safeguards theaters need to keep rigging running without interference. the potential for accidents increases with a wireless device that fails when mobile phones or wireless internet networks disrupt the signal between the remote and line sets.

Manual counterweight rigging basics

Economical and versatile, manually operated counterweight rigging consists of a balanced system of weights and pulleys (figure 2). each set is made up of a batten suspended from lift lines that pass over loft block sheaves,

a head block at one side of the stage, and finally down to a counterweight arbor. the arbor holds weights that are adjusted by the user to balance (or counterweight) the load. movement of the set is controlled by a rope hand line that passes:

  • from the top of the arbor;
  • over the head block;
  • down through a rope lock mounted on the locking rail;
  • around a tensioning floor block; and then
  • back to the bottom of the arbor.

The key to success is to counterbalance the load with steel counterweights. a properly balanced system is inherently safe, as neither load nor counterbalancing weight will move without an external force. the load can be moved with moderate effort by pulling on the hand line. use requires handling of counterweights, and a loading gallery just below the head blocks from which operators can load and unload weights from the arbors.

Counterweight systems can be built in a number of different configurations, based on the manner in which the sets will be operated, how they are attached to the building, available space and stage height, and whether they will be powered by operators or by some form of motorized assistance.

In a single-purchase counterweight set, the weight and travel distance of the loaded batten equals the weight and travel distance of the properly loaded arbor. such assemblies are simple to install and operate, and are very efficient.

In buildings where space for vertical travel of the counterweight arbor is insufficient for single-purchase sets to operate, the counterweight side of the system can be double- purchased. doubling the lift cables around a pulley on the arbor allows the batten to travel twice as far as the arbor. with a shorter travel distance, the arbors can be located well above the stage floor on fly galleries providing space for doors or scenery storage below the arbors and locking rail. however, the arbor

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requires twice the weight as the batten supports.

Double-purchase systems are very useful in some situations, but they are more expensive and more difficult to install and operate. when scenery is added to or removed from the batten, operators must load and unload twice as much weight—adding both friction and inertia to the system, and making it harder to use. while wire rope can last 20 years or more, it is wise to have rigging annually inspected by a qualified professional to ensure all the parts are in top working order.

Arbor guides are required to keep loaded or empty arbors from swaying as they move up and down, with slotted guides called ‘shoes’ mounted at the rear of the arbor to allow it to ride between equally spaced pairs or adjoining j- or t-shape guide rails. for new installations, rigid guides are the best choice— and aluminum j-guides are easiest to align and install, with fewer parts than older t-bar systems.

To counterweight the load on the batten, a loading gallery is a necessity—a bridge above the backstage on which an operator can add or remove weight from the arbor. this must be done at the same time the weight is being changed on the batten, so the system is always in balance.

The load changes while the batten is at floor level—while the counterweight arbor is at its highest level. it is essential to have a loading bridge so the user can access the arbor to add or remove weights to balance the load while the batten is closest to the floor. without a loading bridge, operators are forced to raise or lower the batten in an out-of-balance condition, which can be extremely dangerous. if installation of a loading bridge is simply not possible for the project, motorized equipment should be used instead of manual rigging.

Stage and rigging: The right shape and fit

Rigging can be designed for just about anywhere, but it fits best and most economically in spaces with straight walls and square corners. for theaters used for dramatic performances with set

changes, the stage house height should be two and a half times the height of the proscenium. this allows the scenery and lights to be hidden from the audience when flown.

Rigging sets are traditionally installed on centers that are multiples of 150 or 200 mm (6 or 8 in.). for maximum versatility, the rigging system extends from the proscenium wall to within 1 m (3 ft) of the back wall of the stage house. overall, the rigging layout needs to accommodate the moving curtains, masking curtains, sets for lighting equipment (typically on 3 m [10 ft] centers), and battens for scenery.

Rhe particular project’s structural design, existing conditions, and operational preferences are all factors in determining the choice of block types. upright rigging components are mounted atop structural supports that are usually steel, but also may be made of concrete or other materials. underhung components attach to the bottom flanges of structural steel or the other supporting members. typical structural designs shown in figure 3 are often combined. the project’s theater consultant or the equipment manufacturer can provide information about imposed load capacities to the structural engineer.

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Rigging systems impose both vertical and horizontal loads on the supporting structures. in figure 4, the ‘w’ refers to the maximum load capacity per batten—including the dead weight in the system—and ‘ln’ designates the number of pickup lines in each set. lift lines should typically be spaced at intervals of not more than 3 m along the length of the batten. greater spacing reduces the batten’s load-carrying capacity. on average, scenery batten live loads are a maximum of 37 kg/m (25 lb/ft), with electric batten loads ranging higher, from 35 to 45 kg/m (25 to 40 lb/ft).

Rigging sets for house curtains, fire curtains, orchestra shells, scenery, lighting, and special

effects must be carefully calculated, and their live loads (and full range of travel) must be included in the system’s total design. for example, when a traveler curtain is open, all the weight is concentrated on the extreme ends of the track.

When specifying the support steel, it is important to remember that the frame and head block beams may absorb several times the system’s live load. horizontal bracing is often required on rigging steel. if cross-bracing or diaphragms are used inside the head block beams, careful consideration must be given to their installation to avoid obstruction of the cables that pass between the beams to the equally spaced head blocks above. bar joists are not recommended for the support of loft blocks without considerable alteration and bracing.

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The future

Automated rigging’s move into high schools and colleges is a clear indicator what was once a high-end technology is now a relatively affordable option. school administrators often choose automated rigging because of the safety issues associated with counterweights, which are much more susceptible to operator error than their motorized counterparts. college theater departments often choose automation to give their students the experience of working with this kind of system, which they will be expected to use in professional theaters with increasing frequency.

Whether specifying counterweight rigging or automation, it is crucial to work with a supplier with real experience in the world of theater and performing arts centers. industrial rigging products are not meant for use in lifting weight over people’s heads. theater rigging requires special expertise and a familiarity with its use in live performance situations. selecting wisely allows the benefits in customer safety and satisfaction to be reaped.

This article originally appeared in the April 2010 issue of The Construction Specifier (vol. 63, no. 04), the official publication of the Construction Specifications Institute. Visit
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