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

The safe procedure for rigging a counterweight flying bar is as follows;

The bar number is called to flyperson by whomever is running/calling the rigging from stage level and asks for it to be brought in. In this example lets use bar 10.

Flyperson then calls bar in eg. "Heads on stage bar 10 coming in" brake is then released and rope is pulled down to lower the bar to stage, flyperson will be listening for a call to stop bar when it is at working height.

Flyperson will then apply brake and then attach rope clip which will stop any vertical movement in the cradle they will then call to stage that "Bar 10 is braked and clipped".

When bar is at working height flying piece is then attached, eg. a black gauze.

When all ties are complete on gauze the stage will then call to loading gallery "Can we have 4 weights in cradle 10 please" normally at this point the gallery may ask (if it's possible) for the bar to be brought right in to stage level so they can reach the cradle.

When loading gallery have loaded the cradle they will respond with "Bar 10 weighted"

The stage will then ask for the bar to be unclipped and for the flyperson to take the weight of the bar. The flyperson will then call the bar out eg. "Stand clear on stage bar/ black gauze going out". They must slowly let the brake off and let the rope slip through the brake as it will be cradle heavy. This can be assisted by some crew easing the weight off the cradle by applying weight to the bar. When the bar is to high off the ground for them to reach hemp lines can be thrown over and held to take the strain off the cradle heavy bar.

When the flyperson has flown the piece off the ground the stage will tell them that they are "Floating" and ask them how the weight is, if it is bar heavy then more weight will need to be added to the cradle or if it is cradle heavy then some weight will be removed. If the cradle is relatively light then this can usually be done from the fly floor if not then it should be done from the loading gallery or intermediate fly floor.

When the flyperson is happy with the weights and the bar and cradle are balanced then the bar can be gridded until it is next required.

Parts of the system

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.

Short, Short Mid, Long Mid, Long

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.

Cradle

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.

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.

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.

Blocks

The header block is always the first block on the grid which the lines will pass through, each block after that is known as a loft block.

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.