Part 5. Motorized Rigging
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166 Motorized Rigging Introduction The basic hemp rigging used for the stage changed little from the time of the Greeks until the twentieth century. The need for greater efficiency prompted the modification of hemp to counterweight, which is still the most common type of rigging equipment in use. Today, the desire for increased efficiency and more dynamic scenic effects is fueling a greater use of motorized equipment. Stage-rigging manufacturers combine industrial-grade motors , speed reducers, brakes, controls, and special components to produce motorized rigging equipment for the entertainment industry. A motorized system must be properly designed for its application by a competent engineer. Because motorized rigging equipment is used to suspend objects over people, it requires operational safety devices not found on winches used in industry . Truck winches, industrial hoists, and boat winches are exPart 5 5.01 167 tremely dangerous to use for stage rigging as are homemade systems, unmodified industrial systems, and Rube Goldberg equipment. Do not use them. Most theatrical rigging-equipment manufacturers offer motorized equipment as standard products (figs. 5.1 and 5.2). Escalating labor costs and the equipment’s versatility have helped hasten the acceptance of motorized equipment. Broadway, touring productions, and regional professional companies use motorized equipment as a matter of course. As the cost of motorized equipment has come down in relation to counterweight systems, more and more high school, college , and regional theatres are installing motorized equipment. There is a safety element that appeals to high schools in that motorized systems eliminate the need to load and unload counterweight . Motorized systems are the state of the art in rigging equipment today. It is beyond the scope of this book to describe all of the types of systems in existence. Instead, you will find descriptions of the most common systems in the United States and their specific operating procedures. The operator of motorized rigging does not have physical contact with the moving object that is present when using hemp and counterweight systems. You cannot feel when something changes or goes wrong. Special operating procedures and precautions for motorized rigging must be followed. Systems Descriptions The following descriptions are of general system types. Some of the advantages and problems are listed for each system. A. Motorized Counterweight Systems A motorized counterweight system is basically a counterweight set that uses a motor to do the pulling. The motors do not need to be as large in horsepower as a dead haul (noncounterweight) motorized rigging system. One type requires counterweights to balance the load, so the same basic loading and unloading procedures used for a counterweight set should be followed. Another type of motorized counterweight system is designed to run out of balance, with the counterweight balancing only part of the load. 5.02 168 Fig. 5.1. Electric motorized winches. Courtesy of Peter Albrecht Corp. Fig. 5.2. Electric motorized winches. Courtesy of Peter Albrecht Corp. 169 Fig. 5.3. Chaindrive motorized counterweight set 170 1. Chain-Drive, Wind-on-Wind-off Systems Chain-drive systems (fig. 5.3) use a roller chain attached to the arbor, very much the same way that the hand line is attached to the arbor of a manual counterweight set. The chain goes from the top of the arbor, over a head-block sprocket, down around a sprocket below the arbor, and finally to the underside of the arbor where it attaches. The winch is usually mounted on the stage floor, the grid, or below the stage-floor level. The wind-on-wind-off winch uses a drive cable in place of a roller chain, but the basic operation principle is the same. One end of the cable is attached to the bottom of the arbor, and the other end to the arbor top. One end of the cable winds on the drum as the other winds off (fig. 5.4). Both of these systems are typically used for unbalanced applications, such as electric battens and lighting bridges. This type of system can be designed so that the winches can be moved from one line set to another. 2. Power-Assist Units Power-assist units are packaged units that attach to counterweight systems to automate particular line sets, especially electric and orchestra ceiling sets (fig. 5.5). They are designed either for new construction or existing counterweight systems as retrofits and are not designed to be moved from set to set. They eliminate the need for loading weight on electric sets and make heavy sets much easier...


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