RIGGING SYSTEMS: operation and safety rules

One of the most important mechanical parts of the stage is the fly or rigging system. The "flies" allow for the safe support and facilitates quick changing of much of the scenery and lighting. Fly systems are the systems of ropes, pulleys and winches used for flying things. The flies are considered part of the Carpentry department, but involves its own set of skills so is almost a separate department. Come in several forms. ROPE/"HEMP" HOUSE: Earliest form of theatrical rigging system. Basically, this system was borrowed from the sailing ship industry' majority of the terminology used for rigging systems, including the term "rigging", comes from sailing ships. Headblock Loft blocks _O_ _ _ _ _ _ _ _O _ _ _ _ _ _ _ _ _ _O _ _ _ _ _ _ _ _ _ _O _ _ _ | | | Grid | | | | | | | | | | | | | | | | | | | | | | | | | | _____|____________________|____________________|___ | Batten |_|| Pinrail | ______ Flyrail | | | |_|| Pinrail ___________Stagefloor or Deck__________________________________________ Pinrail: the heart of a rope system. --Taken directly from "square riggers", consists of a wooden rail with holes drilled for belaying pins. Usually a double tiered rail, one pin rail at thigh level and one at stomach level. The lower bar is used to tie off scenery at it's low, or "in" trim. Pin rail may be located at floor level or on catwalk above the floor; called a "flyrail". In modern theatres the main fly system is rarely a rope system, but rope systems are often included as auxillary systems, for temporary rigging and custom rigging needs. Rope systems are far easier to adapt than counterweight or winch systems. Scene loft or fly space: Large open area located above stage. Where curtains and scenery hang out of sight behind the top of the proscenium. Above this space is usually a gridiron, or Grid, on which are pulleys for the fly system. These pulleys are called Blocks or sheaves. Overhung sheave: sit directly on the grid with the pulley (wheel) of the block up. Underhung sheave: gastened above grid to the ceiling, with pulley hanging down. Main loft blocks are often located on pairs of heavy support beams with a gap between, called a loft block well. "Grid", a floor of channel irons or grating filling the area between the wells. Channel irons are suitable for supporting lightweight temporary rigging, called spot lines, between the regular support wells, but not of holding up the normal loads of the main system. Subway grating or similar lightweight metal grate is not strong enough to hold spot rigging safely. In some theatres built on the cheap the grid is dispensed with all together, and the rigging is underhung from the ceiling beams. This makes maintainance difficult and temporary rigging almost impossible. Head blocks: special multiple loft blocks where the multiple lines from the rail spread out over the grid to the individual loft blocks. Head blocks usually multiple blocks, i.e. a single block with several grooves or pulleys, or may be a set of individual pulleys used in association. This last scheme, found in older "hemp" houses, is rarely used today. Traditional material for rope systems was manila hemp rope, usually 1/2" or larger. Being replaced by polyester double-braid rope, stronger, stretches less, reacts less to humidity, rot proof, and has no slivers. Weight of scenery, curtains, lighting hung on battens can be tremendous, sonecessary to counterweight them. On a rope system, generally done using sand bags, literally canvas bags filled with dry sand, securred to the purchase lines with some sort of clew, either a cast iron clew or wire rope sunday. Sandbags come sized in standard increments, e.g. 10, 25, 50, and 100 lb. when filled with dry sand. Can be lightened by partial filling, or several bags can be hung on a clew for more weight. The weight of the sandbags MUST be slightly less than the load on the batten so that the batten will fly down to the deck. At trim, the load is held in place by tying the lines to the pinrail. To work properly, the sundae should be just below the headblock when the batten is all the way in. Note that the batten can never fly out higher than the distance between clew and pinrail when the batten is all the way in. COUNTERWEIGHT SYSTEMS: About a hundred years ago rope systems began to be replaced by counterweight fly systems. Counterweight system consists of a metal frame, an ARBOR raised and lowered by an "endless" purchase line passing over the headblock and under a floating block beneath the rail. The purchase line passes through a mechanical rope lock mounted on the rail which can lock the arbor in place. To the top of the arbor are a set of wire ropes, usually aircraft cable, as loft lines, which pass over the head block to the loft blocks and on to the battens. When line beneath the arbor is pulled down (usually the rear line), it pulls the arbor down, raising the batten. When the other (usually front) line is pulled, it raises the arbor, lowering the batten. The arbor is kept in line of its travel either by "shoes" (slides attached to back of the arbor and engaging a T-track bolted to the wall), or by guide wires stretched between floor and headblock beam and passing through holes in arbor. The first is called a T-track system and the latter a Wire guide system. In place of sandbags, metal COUNTERWEIGHTS are placed on rails of the arbor to balance load. Unlike rope systems, this weight should exactly balance the load on the batten, as the endless purchase line can pull the arbor both up and down. Part of the load on the arbor represents the weight of the empty batten, called "pipe weight", should be left on the arbor when the load is removed. Counterweights usually iron or steel. Some are cast of lead when more weight on a too-small arbor may be required. Counterweights are often referred to as "bricks" or as "pigs", for pig irons. Counterweights come in semi-standard sizes, e.g. 10, 20, 30, and 50 lbs. Lead is cast, perhaps as a 30 lb. brick (about 1/2" thick), A similar steel weight will be about 15 lb. or so. If there are both lead and steel weights in a theatre, leads may be placed on top of the steel but not visa versa, or lead may flow from beneath the weights above them. Types of Counterweight systems Single purchase and Double purchase. SINGLE PURCHASE is simpler and more common. The arbor/puchase line travels between floor and ceiling; arbor travels one foot for every foot of batten travel. To balance a load, must put same amount of weight on the arbor as the load weighs. Everything, travel and weight, is in 1:1 relationship. The main drawback: one entire wall must be dedicated to the counterweight system, as a full floor to ceiling travel of the batten requires full floor to ceiling travel of the arbor. DOUBLE PURCHASE system, lifting lines to loft are doubled back through floating pullies on top of the arbor. The arbor need move only one foot for every two feet of travel of batten. Can therefore be operated from a flyrail located halfway to the ceiling, and still allow the pipe to come in to the floor. This opens storage under the flyrail. The major drawbacks are that twice as much counterweight is needed on the arbor as there is on the batten (2 x the weight, with 1/2 the travel), and loaders typically must handle larger weights. Double purchase systems cost more, are more complicated to use and maintain, and you must have twice as much weight on hand for a full compliment. Also, flymen can't double as deck hands because they are on catwalk overhead. Another place double purchase can be useful is where the side walls are lower than the overhead grid, as with a grid located partway up a gable. A single purchase would not allow full travel floor to grid, but a double purchase with "muled" headblocks would allow full travel of the batten. LOADING PROCEDURE: ALWAYS follow when remotely possible. *Send loading crew to loading gallery (rail). *Flyman calls "Heads UP" loudly and lowers empty batten to floor. *Flyman gives clearance to deck crew to hang load on batten. *Crew loads the batten. *AFTER load is on batten, flyman estimates weight and calls up command to loading gallery to load the arbor with appropriate weights to equal the load. *Loaders raise and secure locknuts and spreader plates, leaving one plate on top of the batten weight, and add required number of bricks. If many bricks are needed, a spreader plate should be slid down between bricks about every two feet or so. *When weights are on, loaders slide down remaining plates and lower and lock off lock nuts, and call down that the arbor is locked and secured. *Flyman calls to deck to "Clear the batten", then carefully unlocks rope and tries to fly goods to see if it is heavy or light. *If weights are off, flyman calls corrections up to the loading rail, who follow above proceedure to adjust weight to suit. *Once weight is correct, flyman calls "clear the batten" and flies batten out to trim, locking ropelock and securing handle with keeper ring. To unload, reverse the proceedure: *Bring in batten, unload counterweights to batten weight, THEN unload the goods from batten. Always call "Heads Up" when flying things in and "Clear" when flying things out. MOTORIZED WINCHES: About forty years or so years ago winch technology began in theatres for rigging purposes. Primary advantages gained from winch driven rigging is that it can be run by remote control by a single operator. Using control console, operator can select and run several line sets at once. Some form of winches can also handle heavier loads than could be operated manually. HOWEVER winches have drawbacks as well. They are more expensive per lineset than other systems. They are more complex than other systems and need more frequent maintainance. They lack "feel"; the operator is disconnected from the piece running and has no direct sense of when trouble is happening. On a counterweight or rope system, you can feel when the lineset hits something or fouls. The first indication on a winch may be when something breaks. For very large loads, e.g. electrics bridges and moveable ceilings, winches can be superior. Winch systems come in several forms. Counterweight/winch system: winch used primarily like a human operator. An arbor counterweights the load, and the winch is used to move the lineset the same way a flyman moves a counterweight set. The advantages to such a system are than the motors can be smaller and can be variable speed so that different flying speeds can be used. The speed can be independant of the load. As long as the counterweight is set properly, the motor only transfers cable rather than raising weight. HOWEVER, still necessary to counterweight load, and in fact the load may have to be more accurately set than for manual systems. The motor may stall if the load is too far out of trim. SYNCHRONOUS WINCH system: there is one winch for each line on a batten, all controlled by the same control signal. For the system to work properly, each motor must be EXACTLY identical in speed to the others or the motors will get out of synch fairly quickly, and pipe will become in crooked. These systems are usually single speed, as it is difficult to create a motor with variable speed and uniform lift capability. Running a motor at slow speed also lowers the power it can put out, so the motor will stall under load. The biggest drawbacks are expense of all those motors and the ease with which they get out of synch; even small variance accumulates over several runs. The most common place such systems are used is multi-use auditoriums where portions of the aud. ceiling can be re-configured for different acoustics. Work because loads are predictable and the motors can be carefully tuned. CHAIN MOTOR RIGS: a form of synchronous winch system commonly used for arena and theatrical show rigging. Consist of industrial chain hoists, typically one or two-ton models, rigged to run inverted, and used in sets to lift trusses or other loads. Most chain motors are designed to be hung from the ceiling, but theatrical chain motors are modified to be attached to the load, with chain hook attached to the ceiling. Really the same motor with the contactor inverted. These motors are fairly consistant in speed over their entire load range, and are single speed only. They are NOT identical, but they can work because: a) they are set up and taken down regularly so that the accumulated errors don't add up. b) they can be run both individually and together, so that single motors can be adjusted to line up with the others. Disadvantages; they do get out of synch quickly, are noisy, and are slow. BUT, they do allow you to fly heavy loads (in multiples of a ton) with a system that can be quickly set up anywhere overhead can support the load and accommodate the chain attachment points. SINGLE MOTOR AND SHAFT: another type of winch often used in theatres. Motor turns a long shaft which raises all the lift lines on a batten or truss. Used for most motorized lighting bridges. Also used to lift the large lineal loads. This system is big, heavy, noisy, and slow, and runs at one speed only, BUT Allows safe movement and of heavy loads without need for counterweighting. Other terms: SPOTLINES deserve special mention: special purpose temporary rigging sets, usually with one liftline holding a single object, such as a chandelier. Spotlines are often rigged as cable picks or pickups to carry a bundle of electric cables offstage. Spotlines may also be rigged for linesets in out of the ordinary positions, as for battens run diagonally across the stage. Spotlines are typically rigged using rope system rigging, but can be done with chainmotors, winches or counterweight arbors as well.

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Last modified: ***, 2002
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