tension wire grids

[tivoliproduction]

one of the local venues in my area has recently had a huge refurb which included the installation of the worlds largest tension wire grid. I was on a walkabout there before xmas and one of my staff who was with me at the time asked me because all the lamps are now above the grid do they still need safeties? I dont know the answer. does anyone else? effectively the tension wire grid has holes approx 3" square so im not sure. anyone any suggestions? :(

[Bryson]

I'd say that safeties actually present an additional hazard in these circumstances. They're small enough to fall through the mesh if dropped, whereas a lantern isn't. If it were my risk assessment, I'd say no. In fact, I'd go as far as to say that safeties were not allowed.

[AndrewR]

We also have a large cablenet instalation, I agree with Bryson about not using safetys (although I have never wasted my breath putting my point of view to my head of department).

 

As a matter of interest, how big is the net?

[tivoliproduction]

im not sure how big the actual cable net is, all I know is that they used over 35 miles of steel rope!! (6mm I think) :( I will try and find out the actual area when I speak to the bloke next.

[tour monkey]

As a matter of interest, how big is the net?

 

I would hazard a guess at this being a venue I have recently worked in as part of a visiting company. As for the size, the grid covers the stage area (up to 60 feet square I think) and the entire auditorium, which I believe can seat over 4000 people... So large would be an understatement!

 

Olly :unsure:

[Barney]

I agree with Bryson. My personal risk assessment would say that safeties are not needed on luminanires. Or indeed on anything that can be caught by the cablenet.

 

However, I would not go so far as to say they are 'not allowed' as I would justify their use on anything that can slip through the holes. For example, some effects projects lenses will fit through a 3" square (diagonally) and you would want to make sure that these were secured. Even if it was with a less 'robust' safety wire.

[robloxley]

My personal risk assessment would say that safeties are not needed on luminanires. Or indeed on anything that can be caught by the cablenet.

What about very heavy items? - is the tension wire grid designed for such a use?

[TomLyall]

I've thought this from the start, but not voiced my opinion until now.

 

How far below the lighting bars do these cablenets usually sit?

 

I see no valid argument for not using safeties, even with a cablenet. What even happened to "belt and braces"?

 

I disagree with the argument about safeties being another hazard, a safety is not much more of a hazard than a colour frame or iris. A safety could probably only fall during rigging, in which case, no-one should be below you anyway.

 

I'd be concerned about having a lantern drop, maybe 4 or 5 feet onto a cablenet. Also, what if said lantern was caught by the power cable first, it could easily rip the lantern apart, shower everyone below with hot bits of shattered lamp etc?

 

So, I'd prefer it if we reduced the chance of any lantern dropping any further than necessary.

 

Tom

[paulears]

well, unless the thing falling off is as much as a person - is that an issue? The extra from the item falling a foot at most shouldn't be a problem here - anybody know what the safe walking weights for these things are - two burly blokes together?

[Tomo]

If you are using captive safeties they can't fall off the lantern.

 

A lantern will usually survive a drop onto a safety - the bond dies, but you'll want to keep the lantern.

Will a lantern survive being dropped onto the cablenet, and many lanterns have fairly sharp edges - could it damage the cablenet?

 

And a moving head will definately die if dropped a couple of feet onto the cablenet, and may well smash into bits small enough to fall though the net - it'll probably be fine when dropped onto the safety.

[Rich newby]

another thought, if a lantern were to fall, and is then caught by its power cable,what would happen if the cable broke at the lantern end, and as the net sprung back up, the live ends of the cable we to contact the net, making the whole thing live! Sure it would be turned off almost immediately, but if there was anyone up there during the show, simply touching or leaning on the net would give them a shock.

 

Just a thought

Rich

[gareth]

Let's not lose sight of the original question in this topic - which was whether lanterns rigged above tension wire grids need safety bonds. Not whether or not the bonds are a problem, but whether they are actually needed as a secondary suspension.

 

And the answer, as far as I can see, is a resounding no. A TWG with a 3-inch mesh isn't going to let a lantern fall through, is it? And all the TWGs that I've ever been on have the LX bars at somewhere around waist height above the mesh, meaning that the noses of the lanterns, when rigged and focussed, were just a few inches above the mesh. (Or, as in one particularly badly-thought-out wire grid in a venue which uses narrow-angle Source4 Zooms FOH, the lantern noses were actually touching the mesh! See, now that's why we need theatre consultants! :P) So if a lantern did slip off a bar or separate from its suspension, it would bounce off the mesh before the safety bond had a chance to pull tight.

[AndyJones]

I know its a little :P and I aplogise to the mods **gets down on knees**

 

BUT

 

does any one know of any tension grids in the South UK I would like to have a little look at one just to be nosy and see what they are like

 

cheers

 

Andy

[AndrewR]

Firstly, as to the loading of the 'nets. We have two separate 'nets (one above the stage, one above the pit/forestage about 4 foot higher) And they are rated to 4 persons each. (although I am informed by the crew that during the installation a few more than 4 blokes were bouncing on it like a trampoline to fit hoists etc.)

 

As to belt and braces. clamp + bond = clamp + 'net.

I only use one bond per lantern, and the 'net will do the same job.

 

Any item that could fit through the 'net should be bonded (same as with scrollers not above a 'net) same as any tool should be attached to the person using it.

 

I agree that movers would be damaged by a fall onto a 'net. And there is always the possibility of damage to the 'net itself.

 

And finally; the 'net should be earthed, your equipment should have proper electrical protection and your lanterns should be rigged so that the bond (or 'net) takes the impact not the cables.

 

Oh and be very careful when hauling chains for hoists through a 'net :P

[Andrew C]

does any one know of any tension grids in the South UK I would like to have a little look at one just to be nosy and see what they are like

The Nuffield in Southampton have an early example.