Magazine article Stage Directions

Finding a Balance

Magazine article Stage Directions

Finding a Balance

Article excerpt

What you need to know about motorized rigging and safety-related issues.

For both artists and tradespeople alike, the theater can be an inherently dangerous place to work. The greatest potential for injury is during a scene change, where thousands of pounds of scenery are moving on and off the stage, performers are rushing to change and return, stagehands are moving furniture, checking effects and setting props, and it's pitch black.

Currently, in most U.S. theaters, flown scenery is attached to a manually operated counterweighted rigging system. The rigging is controlled by stagehands, who receive valuable feedback through a handline regarding the scenery's location and whether or not it has encountered something in its path. In many theaters, the Hymen are the most experienced people on the crew. They know the shows as well as anyone on the production staff. They have attended the rehearsals and are intimate with all elements of the scene change. They can anticipate problems and have a knack for keeping people out of danger. So how do we get a machine to do everything that humans do? Well, we can't, but we can take steps to both meet the performance requirements and keep the rigging systems as safe as practicable.

Motorized Rigging Systems In most motorized rigging systems, the scenery load is not balanced by counterweights, and there is no direct human interaction with the hauling lines. The design parameters for a motorized rigging system vary greatly from a manual counterweight system, where the goal is to balance the load. Motorized rigging systems fall into three basic categories: lineshaft, drum and counterweight-assisted. They are further delineated into two types: fixed speed and variable speed. The type of system, fixed or variable speed, determines the control parameters, which are fairly universal across each category. For the last 50 years, fixed speed systems have been popular for certain applications, such as raising and lowering very heavy "lighting bridges," framed portals and large movie screens over stages. Fixed speed systems, however, are usually operated when there is no audience in the house and no performers onstage. Even then, their operation is generally preceded by a hearty cry of "Heads up!"

During a live performance, the demand for speed, precision, repetition and lifting heavy loads, coupled with the requirements for a silent operation and an accident-free production sequence, place huge demands on the safety of high-speed (i.e. variable speed) rigging systems that can be daunting to both initiate and maintain. Generally, when designing motorized rigging systems, the intent is to have them come to a full stop to maintain safety (i.e., a fail-safe position), but this can be in direct conflict with the demand to (1) keep a performance moving at its assigned pace; and (2) design each machine for its "worst case" (i.e., maximum load) scenario. However, there are limits to the degree of safety that can be achieved in any human-to-machine interaction.

Major Factors Governing Safety

System Design. The person who assembles the parts of the rigging system into a cohesive unit is crucial to its ultimate outcome. The rigging system designer is the person who determines how people interact with the system and how the system responds-taking into account production requirements and machine limitations. It is not unusual to see motorized system specifications that require each lineset to lift 1,000 pounds at a rate of four to five feet per second, and attain full speed within one second after the "go" button is pushed. By necessity, the interests of safety and production quality are best served when the systems designer (an engineer) has a complete understanding of the stage operations and the production demands.

Software or Soft Limits. Today's typical automated rigging systems are so sophisticated that they require a separate computer control distinct from the essential machine operation control. …

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