Stage Rigging 101
Apr 3, 2010 12:00 PM, Lawrence Graham
As in any other subcontracting specialty, the installation of the stage rigging will be no better than the contractor's actual work. The rigging steel may be designed and erected as perfectly as is humanly possible, and the construction documents for the rigging itself may be exemplary, but if the installation is not good, all will be for naught.
It is an unfortunate fact that many, but not all, vendors of theatrical supplies and services are willing to sell rigging equipment and even install it with little or no knowledge of its interaction with the structure. All of the rigging failures I have seen have resulted from operator error. However, damage to the structure has always resulted because the rigging interfaced poorly with the structural elements themselves.
The answer to this conundrum is to write specifications that limit fabricators and installers to those who can demonstrate a satisfactory performance history. Specifications should also require the submission of shop drawings, provide for independent inspection(s) of the installation, and call for as-built drawings once the installation has been completed.
So how does one prevent accidents? The first rule is to limit access. Particularly in the case of schools, access to the gridiron and the rigging should be controlled. One of the best ways is to use an enclosed stairway with a locked door. Another method is to key the brake and lock assemblies in the rigging system so that the rigging system cannot be operated without being accessed by a key.
The second rule is mandated training. No one should operate stage-rigging systems until he or she has been thoroughly trained in how to operate them. Contract documents should include mandated training, and the owner should be advised to have an ongoing training program for new hires and a refresher course for existing operators on a regular basis.
Routine inspections are needed. Before any production opens, the rigging should be thoroughly inspected by a knowledgeable stage technician. It should also be inspected yearly by an outside inspector, and a written report on its condition should be submitted to the owner.
Jean Rosenthal, the Broadway lighting designer, once said, “The theater is a dangerous place. Until you recognize that fact, you are not likely to produce much excitement in it.” She was right, and much of that danger is inherent in the operations that involve the stage rigging. However, careful attention as to how the structure is designed and how the rigging is installed can greatly reduce the chance of failure or accident.
Lawrence Graham, A.S.T.C., is a senior consultant at CDAI with more than 40 years experience in theater design, consulting, and project management. He has a master's degree in theater arts from the University of Tulsa. Graham is a member and past officer of the U.S. Institute for Theatre Technology.
Professional engineers encounter other types of rigging in theaters, ballrooms, arenas, general-purpose auditoriums, and churches. The following are three examples of audio and video rigging issues.
Loudspeakers and speaker clusters are often encountered in assembly facilities. For the structural engineer, obtaining an estimate at the beginning of the structural-design process of the probable load is an important consideration. In addition, designing access to the speaker clusters becomes vital when installing, aiming, and maintaining the speakers. If not well designed, these areas are often not easily accessed once the auditorium's fixed seating has been installed. In these instances, catwalks and work platforms become a necessity, requiring additional expense.
Installing the speakers themselves involves the use of various kinds of rigging components. Collectively, these components are usually referred to as a harness. Each harness interfaces with the structure at a minimum of three hard points and perhaps more. In larger venues, most speakers are assembled into clusters that must be carefully aimed in order to provide the appropriate coverage.
Most loudspeaker manufacturers provide connection points in the speaker cabinets where the harness can be safely attached. Obviously, attaching the harness to other parts of the cabinets is not a good idea — it could void any warranty and may be hazardous.
The least desirable kind of harness, from a safety point of view, is a harness fabricated by an installer in the field. This sort of work, no matter now carefully undertaken, presents many opportunities for human error. Harnesses made by specialty rigging companies provide a much better solution. The best possible harnesses are those made by the speaker manufacturers themselves. Factory fabricated to interface correctly with the manufacturer's speakers, they offer the additional advantage of being able to aim individual speakers within a cluster.
Projection screens, particularly large ones, can impose loads on the structure serious enough to warrant careful evaluation. Compared with speaker installations, installing projection screens — even very large ones — is relatively simple.
Projection screens can be grouped into three categories: framed screens that stand on the floor, framed screens that hang from the structure, and roll-up screens that hang from the structure.
Screens that stand on the floor impose no serious load and can be handled with normal floor loading. Hanging screens, whether they roll up or not, come with built-in attachment points designed by the screen manufacturer. The interface between the screen and the structure is usually a cable or chain. The location of the screen, the number of attachment points, and the estimated live load should be estimated early in the design process.
The actual installation of the screen should be undertaken by a qualified rigger, and the type of chain or cable — and the method for securing it — should be carefully specified as a part of the design documents. Video projectors in larger venues are often quite large and must be located to provide an essentially straight shot at the stage so that the image will not keystone or be distorted by the projection angle.
Usually, that means providing a projection room in an appropriate location or having the projector drop from the ceiling to the appropriate projection location. In the latter case, a projector lift is incorporated into the building design.
Projectors require regular maintenance, so the point of maintenance becomes an important issue. In large venues, it is often wise to provide a catwalk to the lift and configure the lift so the projector can be serviced at that level. In smaller installations, the lift can be configured to be lowered to the floor for access to the projector. In either case, early planning as a part of the structural design is essential.
Rigging of systems for lighting, loudspeakers, video products, trusses, and scenery in stage production applications is inherently dangerous and should not be undertaken without a full and complete understanding of the principles involved. This article is an overview of some of the aspects in the subject of rigging but should not be construed as a designer's guide. Before undertaking any installation in which rigging is required, it is imperative that a mechanical engineer with the proper permits for the locale and any licensing required be consulted so that you are not subject to liability and the consequences of improperly installing these systems. S&VC, Primedia, and the author of this article assume no liability as to the statements expressed or implied within this article.
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