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Lighting bar rigged from roof truss


Charlotte_R

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The amateur dramatics group that I'm a part of work in a church hall and have a front lighting bar which is a piece of scaffolding hung on (long) double ended hook clamps which are hooked over the roof trusses - there's no fastenings.

 

I know this is vague, but I'm just a little concerned that I haven't seen any paperwork with SWLs, etc and that the lighting bar rocks significantly. Can anyone offer any advice as to whether this is acceptable?

 

If not, what are the (preferably cheap) solutions to this?

 

Thanks,

 

Charlotte

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What sort of lanterns are hanging from the bar? The solution required will vary significantly depending on the overall weight.

 

There are lots of different kinds of girder clips and clamps which might give a more secure fastening, but that won't solve the doubts about the capacity of the trusses. If you're hanging a handful of lanterns off a massive girder, the additional weight will be trivial, but it's hard for anyone to pass judgement without seeing the arrangement in the flesh.

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I suspect that if it's the usual lighter weight older fashioned roof steelwork in typical church halls, it's essentially two inch 90 degree angle. Hanging a double ended hook clamp on this suspending a bar with a few lighter weight bits of equipment suggests that the only unknown is the weight capacity of the original steelwork. The real risk in practice is more likely what happens when somebody wheels a lightweight zip up tower across the floor, hitting the bar and potentially knocking it off. If you can stop that happening, then that part of the risk is covered.

 

Every non-engineer will have their own experience based 'stop point'. Trying to think what my own on is, for when I've done things like this, I think its down to if I can lift the bar off the floor to hang it up. As in I could do the job on my own. Something that was heavy enough for me to have to start to use ropes and pulleys and get additional people in would concern me because that kind of weight is hanging on things I don't know how are fixed and anchored. If I could support it safely on two or three chairs, then walk one end up a step ladder and hook it over, then do the same to the other end, then add another clamp in the middle, I'd be comfy. To be honest, proper scaff poles are so heavy that one 6m length of that would push my system - but a piece of ali tube with bar type thinner walls would be a one hander. Hanging a few 650W Fresnels wouldn't then concern me. Like all these things, you just need to keep the consequence and responsibility thing in the back of your head. The point when enough is enough. As I have got older, I've noticed my limit gets lower. I saw some photos of things I did in the early 90s, where now I suspect I would not do the same thing.

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Hi Charlotte, I work for a rigging company based in Birmingham also. The best thing to do is have a competent person take a look at it. I have dropped you a private message if you would like to arrange for me to come down and take a look, and help you weigh up your options. Cheers.
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Thanks for the replies so far.

 

To clarify, it's a substantial wooden structure that I'm personally not too concerned about - it seems well engineered and has been up for about a hundred years.

 

The load is some fresnels, PCs and the occasional profile - so all relatively light point loads (no dynamic loads like moving lights, but I'd like to be able to hang some if productions merit it).

 

My main concern is that the bar is hung from 3 long hook clamps that can't be tightened around the roof truss.

 

Also, it would be nice to remove the requirements to work at height quite so much.

 

Thanks,

 

Charlotte

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I would be very wary about putting anything that moves on the insecure bar. If nothing else, when there is a movement the bar will tend to move and your other lighting on the same bar will be affected as well. It will also highlight to the audience that the bar is not properly secured. These are just my common sense reactions, personally I would have someone who knows what they doing in to check (but then Andy Jones is a personal friend!)

 

 

You have to consider the worst case. Is there anything which could happen which would dislodge the bar? As has already been mentioned this might be ladders or similar moving below it, or anything else tall enough to reach the bar. When you move the tabs or anything else physically on the stage, does the bar swing? Same applies to trains/traffic nearby?

 

I have to admit that like probably most LDs who have lit in similar environments, I have sometimes had to do things that I wouldn't do if I owned the space and could rig something permanent. However, depending on your company's relationship with the venue owners, you might mention to them that a lighting bar is needed at a particular place and a permanent solution, especially without permanent wiring, could probably be put in place fairly cheaply (although you also have to keep in mind any other users of the venue, such as badminton players). If your company made a contribution towards it that might make it happen more easily - and this would probably take movers provided they are included in the planning.

 

The space I had to take shortcuts in (which my company was a stake holder in) was approached in this way and the suggestion triggered some thought into making the venue more usable as a theatrical venue which was supported by cash from the local council. Not only did lighting bars appear, but permanent dimmers and the venue's own lighting inventory!

 

EDIT: This took several years by the way!

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Village halls are replete with this sort of homespun structure and like Paul I have become more wary of them. If I was still active in such things I wouldn't touch anything held in place by gravity like this particlarly as everything to do the job properly is so readilly available now.
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It wouldn't be hard to purchase the bits and do it yourself or possibly get the bits from doughty

Probably just two bits of studding threaded through either angle iron or uni strut in front and behind the wooden beam, with a strut top and bottom to sandwich the bar.Then something similar on the bottom to locate the scaff bar.?

That won't resolve the access though

Any hoist needs inspection which might, be an issue

I am not a structural engineer though!

I assume that you use safety chains? As a temporary measure you could buy some strops of a suitable length and wrap them over the beam, then over the bar, so that if something gets knocked, the strop is a failsafe

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