The house is ‘rigged’Audio/Visual, TECHNOLOGY Monday, October 1st, 2012
By Harvey Sweet
Audio speakers, lighting fixtures, banners, a cross, even a flying angel in a pageant – these are things that may be suspended high above the heads of the congregants in a house of worship. Each of these elements, whether static or moving, is hung from rope, chain or wire rope.
The suspension medium is attached to the structure of the building or to devices that allow planned movement of the piece. The equipment with which any of these elements is suspended is known as “rigging.”
Rigging is used to suspend and move anything, whether lighting, scenery, ecclesiastical equipment, or props for a worship production. Dynamic rigging can raise or lower lighting fixtures into position for maintenance (the replacement of burnt out lamps or faded gels). Scenery can be lowered into a performance area to create a background or raised out of the way to reveal a new setting. Rigging can be done manually or by motorization.
Concerned with safety and efficiency, churches require the same caliber of rigging equipment that theaters use. This equipment is governed by strict safety standards published by the PLASA and ANSI organizations.
These standards determine the appropriate suspension medium. For example, if you are going to suspend a stationary cross on galvanized utility cable (GUC) – formerly known as galvanized aircraft cable – you must apply a safety factor of 5:1.
Nothing should ever be suspended above people on a single supporting line, no matter what the material. Rigging requires redundancy. Heavy objects, such as a large crucifix should be supported on at least two lines. Three are preferable. Suppose this is a cross that weighs 500 pounds. Because there are two supporting lines, each line must support half the weight, at least 250 pounds.
This load can be supported by 1/8-inch diameter 7 x 19 GUC, with an ultimate rated breaking strength of 2,000 pounds. To determine the maximum strength of the wire rope, divide 2,000 pounds by the safety factor of five (2,000 pounds divided by five equals 400 pounds). In this case, each lift line will be capable of safely supporting 400 pounds. Two lift lines will safely support a load of 800 pounds if they are in good condition, properly terminated and properly installed. (If this were a moving load, the minimum safety factor would be 8:1.)
The best and safest choice for moving such loads above an audience is motorized rigging with safety features built into its hoists and controls. These machines are typically installed by professional riggers. Not all motorized hoists or hoist controls are equal.
A rigging system, at a minimum, must (1) locate hoist controls in the line-of-sight of the moving objects and (2) include a “hold-to-operate” button so that the lifted load only moves when attended by a person. (3) “End-of-travel” and “over-travel” limit switches must be part of the system to ensure the lifted objects will not crash into the overhead structure or slam into the floor. (4) The hoisting system should include load-profiling capability to ensure that a hoist will stop moving if unexpected excess weight (such as an unintentionally lifted curtain) is placed on the machine, or if normal weight is reduced (if scenery unintentionally were to catch on a ladder or platform).
Additional functionality that should be provided by a motorized system would include preset positioning of battens, speed control of battens, and slack-line detection. Control modes such as automatic cycling of cues, automatic timing between cues, and the moving of multiple line sets at the same time are also very beneficial. The best system provides feedback information (“diagnostics”) from each of the hoists to the controller.
Finally, you should not need a Ph.D. in engineering to operate your motorized hoist controls. While a manual rigging system (raising, lowering and manipulating stage elements by hand) may seem simpler, it requires several qualified persons operating with a high awareness of safety and in a very coordinated way.
Motorized rigging requires only one responsible operator who understands the workings and safety features of the system. Motorized rigging reduces the manpower necessary to run a show.
Automated stage hoists make great worship-production artistry possible – adding energy, diversity and excitement. Churches rely on this technology not only for signature seasonal pageants and special services but simply for their busy facility’s daily needs. Motorized rigging saves time, labor and money, while – most importantly – being safer.
Harvey Sweet is senior product manager with ETC Rigging (Electronic Theatre Controls Inc.), Middletown, WI. [www.etcconnect.com]