Counter Weight Flying

This type of flying allows scenery to be counter balanced by a vertically travelling cradle which is attached to steel wires which run over a series of pulleys in the grid which all terminate on a fly bar. To operate the system control lines are tied off to each end of the cradle, this allows the operator to move the bar either in or out. By pulling the rope down the bar will move towards the stage and by pulling the rope up the bar will move towards the grid.

Single Purchase

“Single Purchase” simply means that to lift a certain load the same amount of “effort” is required.

With a single purchase counterweight set the same amount of weight is loaded into the cradle as is placed on the bar in order to “balance the set”, the weights become the “effort” required to lift the load rather than your arms which is good news for us compared to the hemp sets.

Note in the diagram below that the scenery is supported by 4 steel wires, which are attached to the top of the “cradle” which we now know holds an equal amount of weight.

The set is considered to be correctly weighted (balanced) when an operator can, let go of the control line and neither the scenery nor the cradle move.

The control line ( or "hauling line" as marked in the diagram) allows the operator to control the movement of the cradle, and therefore the scenery. The rope is moved in the same direction as the travel of the bar, i.e. when the rope is pulled down the bar will travel down toward the stage floor and vice versa. The cradle also moves exactly the same distance as the bar but in the opposite direction i.e. when the cradle moves up 6m the bar will travel down 6m, towards the stage floor.

I realise this is fairly hard to understand on paper but you will have the opportunity in the first weeks of term to try out the flying system and then refer back to these notes. I hope they will then become clearer.

Double Purchase

The reason for using a double purchase system is usually lack of vertical space. A Double Purchase system does not need as much height for the cradle, frame and runners as a single purchase system. In the Single Purchase set the cradle, frame and runners need to be the same as the full travel distance of the flying bar, in a Double Purchase system the cradle will only move half the travel distance of the flying bar.

The Double Purchase sets in the New Athenaeum are located above the dock doors into Room1. Since the runners could not come down to the floor level due, to the door, Double Purchase sets were installed.

In a Double Purchase set two lines support the load through a pulley on top of the cradle. Since each line has the full weight of the bar, double the weight must be added to the cradle to balance the set.

The simplified diagram below will, hopefully, begin to illustrate the relationship of weight and travel in a double purchase set.

Rigging

This is the Safe Sytem of Work for Rigging of Countwerweight Sets re-written September 2010. The term "floor manager" is used for clarity but this will normally be the Technical Stage Manager.

1. Personnel must include 1 floor manager, 1 fly person on flyfloor and 2 persons to unload cradle. A member of staff must be present in the venue.

2.. Hard Hats & Steel toe capped shoes must be worn by all onstage during this procedure.

3. The floor manager will instruct the fly person that the stage is clear to bring bar in until it is at a suitable height for attachment of scenic item. The floor manager watches at all times and gives clear vocal instructions to the fly person as the bar approaches the floor. Walkie Talkies should be used where possible.

4. When the bar is at rigging position the flyperson applies the brake and applies a rope clip. Once this is done the flyperson will inform the floor manager that they may proceed with the task.

5. The floor manager may then instruct the attachment of the scenic item, checking all equipment, attachments and fixing points.

6. Once the scenic item is attached and checked, the floor manager will request that the correct number of weights will be loaded into the cradle. Stage crew may be required to maintain downward force on the bar to act as a counterweight against the loaded cradle either manually or by ropes slung over the bar depending on total weight of the scenic item.

7. Once the cradle is loaded the loading gallery will inform the floor manager and flyperson that the cradle is loaded.

8. The floor manager will then instruct the flyperson to remove the brake and clip and fly the bar. Again the crew may be required to act as counterweight until the weight of the scenic item is fully hanging on the bar. This will be the decision of the floor manager.

9. Once the scenic item is hanging on the bar the flyperson will adjust the weights if required i.e. add or remove a couple of weights at the flyfloor to ensure that the counterweight set is “balanced”.

10. Once the bar is balanced the flyperson will inform the floor manager who will then instruct further work plan.

Grid

The highest area in the fly tower, this is where all the loft and header blocks send the steel wires which are attached to the cradle down through the grid floor to the bar.

Loading Gallery

This is where the cradle is at its highest point of travel and so is weighted here.

Intermediate Fly Floor

Level between fly floor and loading gallery this area is used for balancing out cradles and giving assistance with heavy hemp lines.

Fly Floor

Where all the fly bars are operated from.

Flying Bar

Metal bar onto which flown pieces of scenery, lighting, speakers, pyrotechnics etc. are attached to.

The steel lines which are attached to the flying bar, tavel up to the grid, go through a series of pulleys and attach to the cradle via Short, Short Mid, Long Mid, Long steel wire rope.

Cradle

Sometimes referred to as Arbor

A metal frame into which counterweights are placed to counter-balance the weight of a flying bar.

Weights

Weights used to balance out heavy scenery which are placed into a cradle usually in two sizes 'whole' and 'half' weights. Whole weights in the New Athenaeaum Theatre are 12kg and Half Weights 7.5kg. Don't ask :-)

Control Line

The line which is hauled either up or down to move the cradle and move the flying bar.

Brake

The brake has the control line passing through it and when applied is designed to stop any movement in the cradle or bar however they are not designed to, and should never be, holding any of the weight.

Rope Clips

Metal hardware peices used as a secondary safety device when working with counterweight bars on stage. They are used by the flyman to grip the control line to itself. Commonly used during a fit-up or LX rig, the bar in question will usually be flown in to working height, then "braked and clipped" before the weight on the bar or in the cradle is adjusted.

Loft Blocks & Header Blocks

The header block is always the first block on the grid which the lines will pass through (directly above the flyrail), the pulley blocks which sit on the grid are loft blocks.

Hardware

Drifts

These are lengths of steel wire rope which are used to hold scenery to fly bars.

Barrel Clamps

Double sided clamp with circular hole designed to fit round fly bar and hold scenery in place. These can be with the ring attached as in the picture or without.

Turnbuckle

Double ended twisting screw which allows small altertions in the height and level of a flying piece by either raising or lowering it.

Shackles

Used as a joining piece between drifts, turnbuckles and barrel clamps. Usually in two different types:

D-Shackle Can only have force applied on each end of shackle. Good for straight up/down rigging.

Bow Shackle Can have force applied in several directions. Good for multi-angle/directional rigging.

Flying Irons

Attachement between the scenery and the drift, usually bolted to back of flat and then turnbuckled and shackled to drift.