J.R. Clancy Provides Design, Manufacture and Installation of Theatrical Equipment Worldwide                                      1-800-836-1885
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                         
 
Printer Friendly Page
  
   
  Counterweight Rigging Backstage Tour  
 
 
           
     
   
         
Counterweight Rigging Backstage Tour "Automatic Fire Safety Curtain" - A curtain that closes automatically in the event of a fire to prevent heat, smoke and flames on the stage from reaching the audience. "Round Weights" - One weight set tensions the fire line to compensate for normal linear expansion and contraction, while the other exerts pressure against the clutch lever in the opposite direction. If the tension is lost, the second weight set trips the clutch lever, allowing the traction block to spin. "Traction Drive Winch" - Winch with a v-grooved drum that uses friction between cables and the sides of the grooves to engage the pulling cables. Increasing the cable tension causes the cables to jam tighter in the v-grooves. "Safety Chains" - (1) A secondary support line, usually of chain, that supports a fire curtain or other device when the primary support cable become slack for any reason. (2) The extra weight of fire curtain safety chains helps the fire curtain accelerate at the start of its travel. "Lattice Track" - The lattice track in which the fire curtain's counter-weight arbor rides is attached to the front wall of the stage and is totally separate from the counterweight arbors used to control movement of other elements on the stage. "Lattice Track Arbor" - The lift lines supporting the fire curtain are attached to counterbalance weights sliding in their own arbor, thus using gravity to control the curtain's descent. "Fire Lines" - The 1/8-inch wire or 3/8-inch manila rope lines sense the presence of fire and release the curtsain if temperatures rise above a predetermined level. "Fusible Links" - Sections of fire line are joined at half a dozen points along their length by flat pieces of steel that have been soldered together with a low melting-point (165 degrees F, 74 degrees C) metal mixture. If the temperature at any point along the perimeter of the proscenium exceeds this level, the fusible link gives way and releases the curtain. "Sure Guard" - Sure-Guard(TM) is an electro-mechanical device that can be connected to fire detection systems or rate-of-rise temperature sensors. When the Sure-Guard(TM) circuit is broken, it de-energizes a simple electromagnet and releases the fire line. "Dashpot" - Attached to the stage floor, the dashpot is a simple hydraulic braking mechanism that acts as a safety device by slowing the curtain before it reaches head height. "Manual Release" - For added safety, each end of the fire line is held by a steel pin running through a loop in the line. Simply pull the pin, and the fire curtain falls. "Smoke Pocket" - A slot, usually of fabricated steel, that supports a guide system at the edges of a fire safety curtain and that helps to prevent smoke passing around the edges of the curtain. "Pipe Batten" - Usually made in 20-foot lengths, our pipe battens have 18-inch iron splices that slip into the pipe to stiffen and strengthen the joints, thus offering full confidence to support hundreds of pounds of fixtures, scenery or other equipment. "Batten Clamp" - A device from which a load is hung, the batten clamp attaches to the flange of a steel beam without altering the beam in any weight. "Trim Chain" - A length of chain placed between a lift line and a pipe batten or scenic element to connect them and to facilitate minor height adjustment of the load. "Lift Lines" - The wire rope lift lines that support the pipe batten act as the muscles that hold the rigging system together. Galvanized steel aircraft cable is preferred for its strength, flexibility and free-running nature. "Hand Line" - A line, usually a rope, that is pulled by hand to lift or control the movement of a load. "Floor Block" - The hand line runs over the head block and under the floor block. The floor block is adjustable to keep the line taut. "Loft Block" - A pulley mounted to the griiron or support steel that supports and changes the direction of a lift line cable between the load and the head block. "Head Block" - A pulley mounted to support steel that changes the direction of lift and operating lines between the loft blocks and an arbor or winch. "Idler"- A pulley designed to support one or more cables but not to make direction changes. "Loading Gallery" - A gallery above the stage floor where technicians add and remove counterweights from the arbors. Usually located so technicians have access to arbors when battens are at their lowest positions. "T-Bar Guide Track" - Attached to the back of each counterweight arbor is a guide shoe that lets the arbor slide up and down between two T-shaped guides, but prevents it from swinging from side to side. The guide shoe is Ultra High Molecular Weight (UHMVV) polymer backed by a steel plate so it stays rigid while still sliding smoothly and quietly. "Outrigger Batten and Bracket" - Fastened to the wall with a triangular bracket, the outrigger batten is a convenient rest for ladders, scenery, etc., so they won't interfere with the handlines and counterweight arbors. "Rope Lock" - A cam operated device that clamps the hand line that is attached to an arbor in order to prevent movement. Designed to hold the unbalanced load in a set. "Locking Rails" - Rope locks are attached to the locking rail. Erasable plastic index cards that can be used to label the set's purpose are also often attached to the locking rail. "Counterweight Arbor" - Counterweight arbors should be built like a tank, featuring a heavy welded steel top and bottom (with brittle castings avoided at all costs). Threaded 3/4-inch steel arbor rods are attached to the top and bottom plates with double sets of nuts. Spacers should keep the weights from resting on the bottom nuts to prevent stress and wear. "Index Light" - A series of lamps in a special housing designed to illuminate the locking or pinrail area.
           
How Counterweight Rigging Works
A simple counterweight system is based on the principle of establishing a balanced set of weights that allow a stagehand to raise and lower various loads with minimal effort. Complete rigging systems consist of one or more counterweight sets. Each is comprised of a pipe batten suspended from lifting cables which pass over loft block sheaves, then over the head block at one side of the stage and down to the counterweight arbor. Netscape users and older browsers (pre IE 4.0) must click on each callout for a definition.  
Back to Drawing
 
Automatic Fire Safety Curtain
Out of sight? Always, we hope, but never out of mind. The straight lift automatic fire safety curtain system, first patented by J.R. Clancy in 1904, is designed to block the spread of an on-stage fire until the audience can be evacuated. And it should do it without human intervention or electricity. The best curtains are made from ZetexPlus®, a coated fabric that spreads the heat laterally and prevents "hot spots" from forming that could burn through and allow the fire to spread.
 
Back to Drawing
 
Round Weights
Two sets of round weights in the motorized fire curtain system are in a continual tug-of-war. One tensions the fire line to compensate for normal linear expansion and contraction, while the other weight set exerts pressure against the clutch lever in the opposite direction. If line tension is lost, the second weight set trips the clutch lever, allowing the traction block to spin.  
Back to Drawing
 
Traction Drive Winch
The fire curtain lift lines pass through a V-grooved traction block that grips them. The block is connected to an electric drive winch through a clutch mechanism that keeps it from turning. If the fire line slackens suddenly, a lever opens the clutch, the traction block spins and the fire curtain falls.  
Back to Drawing
 
Safety Chains

These heavy steel chains attached to the stage structure will support the curtain should the lift lines fail during a fire. Their extra weight also helps get the curtain going once it has been released.

 
Back to Drawing
   
Lattice Track
The lattice track in which the fire curtain's counter-weight arbor rides is attached to the front wall of the stage and is totally separate from counterweight arbors used to control movement of other elements on stage.  
Back to Drawing
   
Lattice Track Arbor
The lift lines supporting the fire curtain are attached to weights sliding in their own arbor. The weights counterbalance much, but not all, of the curtain's weight, so the curtain's descent is powered by the most reliable force of all - gravity.  
Back to Drawing
   
Fire Lines
The real role of the 1/8-inch wire rope line, or 3/8-inch manila rope fire line is to sense the presence of a fire and release the curtain if temperatures rise above a predetermined level.  
Back to Drawing
   
Fusible Links
Fire lines are not solid pieces of wire or hemp rope. They are sections of line joined at half a dozen points along their length by flat pieces of steel that have been soldered together with a low melting-point (165°F, 74°C) metal mixture. If the temperature at any point along the perimeter of the proscenium exceeds this level, the fusible link gives way and releases the curtain.  
Back to Drawing
   
Sure Guard™
The fire line also can be released by a J.R. Clancy system called Sure-Guard™ . Sure-Guard™ is an electro-mechanical device that can be connected to fire detection systems or rate-of-rise temperature sensors. When the Sure-Guard™ circuit is broken, it de-energizes a simple electromagnet and releases the fire line.  
Back to Drawing
   
Dashpot
A fire curtain in free fall can be dangerous, so the dashpot attached to the stage floor is a simple hydraulic braking mechanism that starts slowing the curtain before it reaches head height.  
Back to Drawing  
   
Manual Release
When lives are at stake, redundancy is man's best friend. Each end of the fire line is held by a no-nonsense steel pin running through a loop in the line. Pull the pin, the fire curtain falls.  
Back to Drawing  
   
Smoke Pocket  
The vertical, guided edges of the fire curtain ride inside the smoke pocket, a wide, but shallow, steel box. Regardless of which way the air in the theater is moving, the curtain is forced flat against the structure sealing the edges of the proscenium opening.
 
 
Back to Drawing  
   
Pipe Batten  
Hundreds of pounds of lighting fixtures, scenery, sound equipment - anything - may be hung from the pipe batten so it had better be robust and rigid. Usually made in 20-foot lengths, ours have 18-inch iron splices that slip into the pipe to stiffen and strengthen the joints.  
Back to Drawing  
   
Batten Clamp  
A device which attaches to the flange of a steel beam without altering the beam from which a load is hung.  
Back to Drawing  
   
Trim Chain  
With multiple lift lines attached to each pipe batten, it is inevitable that their lengths will have to be adjusted to keep the batten parallel to the stage. There are several trimming devices, but the most common is the trim chain.  
 
Back to Drawing  
   
Lift Lines  
The wire rope lift lines that support the pipe batten are the tendons, the muscles that hold the rigging system together. Galvanized steel aircraft cable is preferred for its strength, flexibility and free-running nature.  
 
Back to Drawing  
   
Hand Line  
The flyman uses the hand line to raise and lower the batten. Traditionally made of ¾-inch manila rope, polyester hand lines now provide greater durability, dimensional stability and operator comfort.  
 
Back to Drawing  
   
Floor Block  
The hand line runs over the head block and under the floor block. The floor block is adjustable to keep the line taut.  
Back to Drawing  
   
Blocks  
If the lift lines are a rigging system's tendons, then the loft, head, floor and idler blocks are its joints. Loft and head blocks can either be hung under structural members or mounted upright on a grid.  
 
Back to Drawing  
   
Loft Block  
Mounted overhead at grid level, the loft block is a simple pulley that runs the lift line 90° toward stage left or right. Sealed precision ball bearings allow the sheave to turn smoothly and quietly on the shaft. The groove in the sheaves should be machined or molded precisely so it supports the line through at least 150° of its circumference. This minimizes deformation and wear. Better sheaves have double depth grooves so the line feeds into the sheave securely when the head block is offset.  
 
 
 
Back to Drawing  
   
Head Block  
Individual lift lines are collected by the head block and turned downward in their own groove toward the floor. There also is a separate center groove for the hand line. Head blocks are muscular because they carry the entire load attached to the batten. Tapered roller bearings are a must.  
 
 
Back to Drawing  
   
Idler  
Despite the weight they carry, lift lines will sag as they cross the stage unless they are supported by small idler blocks attached to the loft block sideplates. The closer a loft block is to the head block, the more idlers it carries.  
 
Back to Drawing  
   
Loading Gallery  
The gallery's function is simple - it provides a place to stand while adding weights to or subtracting them from the arbor. It must be ruggedly designed since it has to be capable of storing all the weights in all the arbors, often several tons.  
 
Back to Drawing  
   
Counterweight Arbor  
Counterweight arbors should be built like a tank. Look for a heavy welded steel top and bottom. Avoid brittle castings - there is too much at stake. Threaded ¾-inch steel arbor rods are attached to the top and bottom plates with double sets of nuts. Spacers should keep the weights from resting on the bottom nuts to prevent stress and wear.  
 
 
Back to Drawing  
   
T-Bar Guide Track  
Attached to the back of each counterweight arbor is a guide shoe that lets the arbor slide up and down between two T-shaped guides, but prevents it from swinging from side to side. The guide shoe is Ultra High Molecular Weight (UHMW) polymer backed by a steel plate so it stays rigid while still sliding smoothly and quietly.  
 
 
Back to Drawing  
   
Outrigger Batten & Bracket  
Fastened to the wall with a triangular bracket, the outrigger batten is a convenient rest for ladders, scenery, etc., so they won't foul the handlines and counterweight arbors.  
Back to Drawing  
   
Index Light  
In darkened wings these lights, attached to the outrigger batten, allow the flyman to see what he or she is doing. A reflector hides the light from the audience.  
Back to Drawing  
   
Rope Lock  
Once a batten is positioned “on its mark,” the rope lock holds the hand line in position. A handle-operated cam clamps the line between two metal “dogs,” one of which is adjustable depending on the rope's diameter.  
 
Back to Drawing  
   
Locking Rails  
Rope locks are attached to the locking rail. Erasable plastic index cards that can be used to label the set's purpose are often attached to the locking rail, as well.  
Back to Drawing