Fly system
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A fly system is a system of ropes, counterweights, pulleys, and other such tools within a theatre designed to allow a technical crew to quickly move set pieces, lights, and microphones on and off stage by 'flying' them in from a large opening above the stage known as a flyspace, flyloft, fly tower, or fly gallery.
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[edit] Types of fly systems
There are many types of systems that are made of different materials and operated in different fashions. The most common type in permanent theaters is the counterweight system. Other types include the pin-rail system which relies on sand bags as counterweights and uses a single main pulley to hold the control line, and motorized system which use electrical motors to move a load. Some older theatres use traditional non counterweight systems, referred to as 'Hemp' houses this refers to the material of the ropes. Hemp houses are 'muscle' powered and need a very skilled fly crew to safely fly scenery in and out.
[edit] Counterweight fly system
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[edit] Structure and operation
In a typical counterweight line set, a counterweight-carrying arbor moves up and down a track parallel to a wall. The arbor is attached to several steel cables which weave around a series of pulleys at the very top of the fly tower (above the stage) and attach to a long pipe, or batten that is the length of the stage. The combined weight of the arbor and the counterweight inside it initially matches that of the batten, so both are equally balanced on the series of pulleys above the stage. A long rope or operating line, attached to both the bottom and the top of the arbor feed through two pulleys underneath and above the arbor's entire movement track, allowing an operator to pull the rope up or down and move the arbor and pipe batten with ease.
As more weight is added to the pipe batten (in the form of curtains, scenery, lighting equipment, and rigging hardware), it is counter-weighted by adding more steel weights to the arbor. This enables an operator to "lift" the load on the pipe off the ground and fly it "out" (meaning "up" in theatrical terms) sometimes as high as 70 feet (clear above the stage and above the proscenium). A typical counterweight fly system will sometimes have 50 or more individual parallel sets of lines running up the length of an off-stage wall in a theatre.
[edit] Arbor
An arbor is a steel frame which holds counterweights and is moved vertically opposite of the batten. The bottom attaches to the purchase (control) line, which runs around the tension sheave, through the lockrail, up over the head sheave and back down with the hoisting cables (or lift lines typically made of galvanized aircraft steel cable) to attach at the top of the arbor. The hoisting cables run from the top of the arbor, up around the head sheave, across the stage to the loft sheave (attached to the gridiron (grid) over the stage) and down to the batten. When the arbor is raised (via the purchase line) the hoisting cables slacken, which causes the batten over the stage to lower. Complementary to this process, when the arbor is lowered, it pulls the hoisting cables down causing the batten over stage to raise up.
[edit] Weights
Counterweights are a key part of the fly system. They are placed on the arbor and balance the load being flown; they counterweight it. Weights are usually made of lead or steel and vary in thickness from 1 to 3 inches. Weights are usually loaded from the loading bridge, but can also be loaded from the fly gallery or locking rail. It is customary to paint the weights that counterweight the batten (pipe) yellow; these weights should not be removed. When draperies are flown permanently, their respective weights are also painted yellow. Finally, weights usually have a a flat corner for easy removal. It is customary to stack weights in an alternating manner, with the flat corner opposite to the opposite side as the previous weight.
Counterweights are generally made of flame-cut steel and come in various sizes. The footprint of each weight is approximately identical, but they typically come in thicknesses of .5, 1, 1.5, and 2 inches. Counterweight systems are generally built to use either 4 or 6 inch wide plates. Counterweights are sometimes also knows as 'bricks' or simply 'steel'. Often a rigging worker will simply be asked to load a number of inches of steel, which correlates to a specific weight.
[edit] Batten
A long steel pipe which moves up into the flyspace and down onto the stage, usually parallel to the proscenium arch and to the stage floor.
[edit] Locking rail
A locking rail is located on the stage deck, or on a backstage catwalk, usually perpendicular to the proscenium arch, generally extending from the proscenium line to the back wall. It has a rope lock for each lineset, a built in lever-operated clamp which keeps a balanced load from drifting, as well as a safety lock. There is also usually a headset system or a cue light system to signal the flyrail crew. It is possible to load (add counterweights) from this rail, but it is considered more proper to load weight at the loading bridge.
[edit] Single vs. Double Purchase
Single purchase systems are simpler and more common than double purchase systems. The difference is that instead of the lift lines (wire rope) and operation line (fiber rope) terminating at the arbor, they run through an extra set of blocks and terminate at the head block (above) and tension block (below). This has the effect of giving the arbor a mechanical disadvantage of 1:2 as compared to the batten. The arbor must carry twice the weight of the batten to remain balanced, but only travels half the distance. For every foot of hand line the operator pulls, the batten moves two; this allows for balanced systems to move in and out much more quickly. Because the travel of the arbor is half that of the fly tower, the loading rail could be placed only halfway up, but it is more common to raise the operating rail to that height and leave the loading rail at the top. This allows for open space underneath the entire lineset wall, so that the operating rail can be just offstage but the amount of useful floorspace is not reduced. Note: The operating line is not actually required to pass through the extra blocks for the arbor/batten relationship to change; it is still helpful since it gives the operator a 2:1 advantage over the effective weight of the arbor, which is likely to carry more steel than in a single purchase system.
[edit] Hazards
Conterweightfly systems can be very dangerous if not operated by a competent and trained technician. Runaway situations can occur when the weight on the arbor is not equal to the weight of the batten and its load, especially since it is not uncommon to unbalance the bar to facilitate quick flying in one direction. When this happens, gravity could lift a person off the ground and up several feet in the air, creating both a drop and collision risk. Communication and inspection is key to maintaining and operating a safe fly system. A standard practice in theatre is for the flyman to always call out a warning before flying anything in. This alerts any rehearsing performers or working technicians on stage to be aware that an object is being flown in and to be alert. People on stage generally acknowledge the operators warning by yelling out a confirmation that the warning was heard.
[edit] Hemp Systems
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[edit] Construction
A hemp system, so named for the type of rope that was once used for rigging, is another type of fly system. A purchase line (rope) is run to the grid, with one end dangling for the operator and one end holding sandbag counterweights. A trim clamp, commonly known as a 'knuckle-buster' is attached to the purchase line and the lift line(s) which attach to the scenery or batten. Because there is no rope to pull the sandbags up, the batten is kept a few pounds heavier than the counterweight, so that the scenery can be flown in. A pin rail is used to tie off, or belay the hauling end of a rope. A knot keeps the scenery in place when the set is not moving.
Many theaters have permanent pin rails installed along the edge of the loading gallery, or have mobile pin rails which can be bolted down. the pin rail consists of a large horizontal wooden beam or steel pipe, pierced with vertical pins. the pins are either made from hardwood, or smaller pipe, and may either be fixed to the rail or removable. The pins provide a quick and safe way to tie off the rope. There is a specific way to tie off the rope which puts friction on the rope both from itself, and from the pin rail. this creates an extremely safe knot which is very hard to undo without the specific intention to do so.
[edit] Advantages
Hemp systems are generally cheaper and easier to install in a theater. They can be more easily configured for spot rigging, where the lift lines have to be reconfigured frequently. Some also argue that they are safer for use in theaters because it is much more difficult to get the line set out of balance, causing a dangerous runaway. Sand bags are not able to rust and have no sharp edges.
[edit] Disadvantages
Hemp systems can be more difficult to operate, requiring stronger and more massive fly workers. Some also argue that they are less safe than their counterweight counterparts because it is easier for a misguided technician to disassemble an important part of the system. Sand bags can occasionally fail and spill sand over the stage.
[edit] Motorized fly system
There are two varieties of motorized fly-systems. One incoporates the above arbor and lineset group through use of a winch motor located below the locking rail. The other is more similar to an elevator winch using a cable drum between it and the counterweights with no control rope involved. The first can be attached or detached from the linesets depending on use. Winches are helpful when it comes to moving linesets that are extremely heavy, such as an electric, which with the pipe, circuit raceway, and lighting instruments can weigh close to 1,500 lbs. However, many motors can only move the linesets about half as fast as a flyman at a decent pace, and thus are not used without need of horsepower or remote operation. Additionally, a chain winch can be hung from the grid or a pipe and uses lengths of chain to fly objects out without using an entire batten.
Many modern large theatres use motorised system without the aid of counter weights at all. The batten is connected via wire rope directly to the drum which is powered by geared motor sets. Speeds in excess of 2000mm/s with loads, again exceeding, 1000kg are possible and only limited by the availability of power, current and space for larger motor gear box units.
Computerised or PLC control systems have become quite common place. Millimeter accuracy, safety and repeatability are amongst the advantages of such systems.
[edit] Parts of a Fly System
[edit] Grid
A grid is a steel lattice or slotted (wood or steel) beam floor at the top of most flyspaces, which allows technicians to walk over the fly loft, and configure lift lines and loft-blocks (the final pulley which lets the horizontal lift line coming from the head block to hang vertically and move a batten.) Not all fly systems have a grid due to height limitations. In these theaters, the battens are generally in permanent locations.
[edit] Loading bridge
Specific to a counterweight system, the loading bridge is a catwalk located directly above the locking rail(s) at grid level and allows a technician to add or remove counterweights from a line set to keep the arbor and batten balanced. The floor of the loading bridge holds a large number of counterweights stored for use.
[edit] Fly tower
The fly tower is a large space above the stage where fly lines are raised to, putting them out of the audience's sight. In a full flyspace, the tower is at least as tall as the proscenium, allowing a full-height set piece to be stored. The grid and/or loading bridge are located at the top of the fly tower.
[edit] Deck Rail
The place at stage level where a locking rail or pin rail is built to allow a fly crew to operate the rail. Also sometimes called a flyrail.
[edit] Mid Rail
A locking rail or pin rail located above the level of the stage allowing the fly crew a better view of the stage and also conserving space for actors and sets.
[edit] Common fly system uses
[edit] Electrics
Electrics are special battens with raceways built across them allowing lighting instruments to be hung and connected to remote dimmers. These battens often can also support microphones or special effects equipment. Electrical battens are permanent fixtures with cables hanging from the grid. There are normally 3 to 4 with the last one being the cyclorama. Additional battens can be used as electrics as well, although this can create a problem with wiring, as there are no circuits permanently run to most battens. Multicable is one solution to the problem of wiring to these battens.[1]
[edit] Sets
Soft painted drops can be flown in to depict a background. Solidly constructed sets can also be flown in and hung above the stage or set in contact with the deck. It is not uncommon to see an orchestra shell being flown using the fly system. Larger, multi-use theatres that must convert the stage from a drama theatre to a concert hall make use of the fly system in this way. A batten could also be used to hang pieces of a set, such as a moving stairway or bridge.
[edit] Drapery
Teasers, travelers, legs, cycs and scrims are all commonly flown in drapery used to mask the stage or provide a background.
[edit] Safety
Because fly systems involve such large amounts of weight, and particularly because the weight is usually over people, there are a number of common precautions taken to ensure safety and reduce injuries in rigging.
[edit] Calling Movement
In most theaters, when a line set is moving the operator is expected to inform everybody (with the obvious exception of performances and some rehearsals.) The rule for what they call depends on the theater, but usually includes what is moving and which direction it's moving. A particularly verbose call may sound like "Line set #3, first electric flying in to the deck, downstage." This is shouted so that everybody on the stage can hear it. In many theaters anybody working on stage is expected to respond with "thank you." Furthermore, some operators will call again, "Line set #3 locked," letting everybody know that the set has stopped moving and it is safe to be under it.
[edit] Runaways
In the rare event that an unbalanced line set is allowed to gain too much momentum for the operator(s) to stop it, a specified runaway procedure is to be followed. Typically the venue has established a standard call for this event as well. It may sound something like "Runaway 47, upstage, heads." Operators are trained not to attempt to stop an out-of-control set but rather to call it and get away themselves. The reason for this is that it is unlikely that they will be able to stop it, and very likely that they will burn their hands or be lifted up by the line set, hitting their heads on structure above them. Furthermore, this would put the operator near the batten, arbor, or sandbag as it crashed into the floor. Spreader plates are used in counterweight arbors to keep the two pipes from bending and releasing the counterweights in the case of a runaway.
[edit] Loading Procedure
When loading a batten, or arbor in a counterweight system, it is imperative to control the balance of a set. The line set should be balanced before loading begins, then the batten flown in, the set added, and then the counterweight added from the loading bridge. The specific order is important because it keeps the set from being unbalanced in a position where it could runaway. When it is batten-heavy (after the set is added, but before the counterweights) the arbor does not have anywhere to runaway to as it is already at its grid stop (the upper end of the track) In cases where the set is too tall for the batten to be all the way in, it should be kept as far down as possible. It is always best to add the load in pieces as small as practical and counterweight them one at a time so the system can never get too out of balance. Improper loading procedure is a common cause of accidents in many theaters.
[edit] References
- ^ Gillette, J. Michael (2003). Designing With Light: An Introduction to Stage Lighting, Fourth Edition". McGraw Hill, 84. ISBN 0-7674-2733-5.
