Tsm flying bridge

Brief

The aim of the game here is to rig a 7metre by 1metre bridge which is suspended 4 meters above the stage floor. During the course of this project I hope to illustrate how to suspend a bridge in the New Athenaeum theatre or indeed any theatre.

The Bridge Itself

The bridge could be made from many different materials, wood, steel, aluminum, titanium if you really wanted to. In this case it will be constructed from aluminum. It will be constructed in two sections each of 3.5metres by 1metre this is simply for the ease of construction and transportability. I was originally going to have the bridge made out of box steel but this material is a lot heavier then aluminum, so I went for the lighter option.

The look of this bridge is to be industrial like the bridges that use to be in factories. So it will keep its metal look and to hide the drifts they will be dressed with long link chain.

I know I am no an engineer but after a bit of research of gangways and access walkways this is how I think the bridge would be constructed

This picture shows how gangways for ships are constructed, depending on the designer the diagonal supports can be replaced but vertical ones. The hand rail will sit at a height of 1.5metres high.the floor will be covered with a 3mm aluminum sheet.

Rigging Equipment

I was having trouble calculating the exact weight of this bridge for 2 reasons.

I am no completely sure of how to construct the bridge, therefore how much aluminum would be required. Secondly how many people would be on this bridge at one time?

So for these reasons each of the 8 points suspending this bridge will take at least one tonne. You would think this would affect the cost of rigging by a fair wee whack but it doesn’t really. For example 5mm 7x7 wire core has a MBS(minimum breaking strain) of 1.62tonne costing (insert one I get a quote) compared to example 3mm 7x7 wire core has a MBS 0.58tonne costing (insert one I get a quote).

4 motor chain hoists- sm10 508V2-V capacity 500kg

8 lengths of 8 meter drifts, 5mm, 7x7 wire core, which have been threaded thru long link

2 lengths of 5 metre drifts

18 shackles at 1.50 tonne

4 beam clamp at 1 tonne

4 clutch chain 1 tonne 3 metres in length

4 round slings 2 tonne at 1metres

2 two Leg Bridle 2 tonne 12mm 6x19 (thimble termination)

8 M20 eyebolts

Note motor chain hoists could be replaced with the academy’s new automated winches.

Rigging process

First things first is to get the hardware up to the grid.that is 4 motor chain hoists 4 beam clamps 4 clutch chains 4 round slings

the challenge here is getting the motors up to the grid. Easiest way to do this is to take the motors up the lift the the prompt side fly floor then lower a line down the ladder and pull the motors up onto the grid. Once they are on the grid they will be put into position. the power for the motors will come from the dimmer room were there is an free 200A supply, so cables will have to be ran from the grid down to the dimmer room on the prompt side fly floor.

once the motors are in place the two sections of the bridge will be bolted together. the sections will be held together with 6 bolts, M10 ,and nylon lock nuts.

The chains will be dropped down to deck level, thru rhe gaps were the pick ups for the bars run.once the chains hook is at working level the attached the hook to the 8m drift which has been dressed with the long link chain which in turn is shackled to the bridge via an eyebolt. This is repeated for each motor. Then the slack of the drifts is taken up but the bridge at this stage does ot leave the deck. Now the hemp pick up lines would be droped in for the drift pick ups.to the hemp pick up the 5m drifts will be attached, then the 8m drifts dressed in long link chain which are then attached to the master link of the bridle then the bridle legs shackle on to the eyebolts of the bridge.the slack is then taken up.

Now that the bridge is rigged up, lets get this bad boy in the air. So on the 4 motors we bring the bridge towards the grid, past the 4m mark so there is enough slack to rig the drift pick up lines so they can be attached to clutch chains on the grid. The clutch chain will be rigged onto the beam clamps on opposite sides. They will be joined together with a master link, which will sit above the desired positioon of the pick up which will be shackled onto the master link aswell. Once the drift pick ups have been attached to there anchor points the 4 motors will be lowered untill the drift lines take the weight of the bridge.A spotter must be used because if the motors lower too much past the fix pic up hieghts this will add more tension than they are meant to take!!!! Because the drift pick ups are a posific size this should mean when they are all takin the tension of the bridge, the 4 motors should be all at the same height, in theory. If this is not the case it should be esay to see which motor needs to be lowered because the drift nearest that motor will have slack on it.

To make sure the bridge is completely level a spirt level can be used and by fine tunning the length of the chain hoists.