Rigging lights on a pole grid

[moosch]

Hi there,

I have a couple of questions.

Firstly, could anyone please give me some advice on load distribution. We have a small pole grid around 10 x 4m, for a filming studio.

The weight load rating is as follows: 200kg SWL, U.D.L., no other information. 

I'm trying to figure out how to evenly distribute that weight per pole? Do I divide 200 by 4 (number of poles) and then divide that figure by meters of the pole?

Also, I'm assuming it's not good practice to rig anything on the corners or can I do that providing it's balanced?

 

Second question is, I'm looking for some good practice and legislation around rigging lights on similar grids. We're not likely to rig anything heavier than 27kg (Arri Skypanel S120), but want to create some guidelines for good practice around this. Any pointers would be much appreciated.

 

Many thanks!!

 

[Stuart91]

My first port of call would be the company who installed it (assuming you can track them down). 

Sometimes the weight rating is determined by the strength of the fixings (and the structure the fixings are into) rather than the bars and hardware themselves. 

[Brian]

19 hours ago, moosch said:

...around 10 x 4m...200kg SWL, U.D.L., no other information. 

That feels like a very low SWL for such a large grid but without the missing 'other information' any advice here is going to be guesswork.

[Bryson]

I was just thinking that sounded very low.  Some clarity from the original installer might help.  Does the sign have who installed it on it?  (We make them declare it on the signs on our jobs.)

[paulears]

I'm struggling to picture this - you have a 10 x 4m presumably aluminium or steel staff tube grid, ground supported on 4 vertical staff poles? 200Kg as a total for the whole top grid seems quite low, considering the actual metalwork is probably heavier than that - so the 4 support tubes are carrying a permanent higher load. A typical 10m steel tube with 3 supports - 1 centre, one at each end flexes quite a bit with a mid span distributed load - but 200Kg for the 10m length would be pretty normal. If your grid is based on 1m 'squares' then that's 1000Kg for the five 10m lengths is it not?If you only have three longitudinal tubes up top then you have 600Kg? Purely from the ones I have seen, 4 verticals for 10m length is a bit of a stretch. My studio has smaller dimensions and the longest unsupported span is 6m between the vertical ground supports and my just over 100Kg weight deflects it around just under 10mm centre span - as in not uniformly distributed. I'm not clever enough to calculate the capabilities of your system, but a second opinion could be worthwhile. 

I work with a firm of engineers quite often, and up in a roof, I asked him one day what could I hang from a useful point in the roof steelwork. He looked, then said how much do you need? I asked for 300Kg - a random figure I thought sensible. Immediately he said no problem - did I want a piece of paper? I asked why he was able to say yes so quickly. He pointed to the junction of the steelwork - with bolts and said if you'd asked for 2 tonnes I'd have said yes just as quickly. The steelwork was even at first glance capable of much, much more. I don't even have the skill to roughly assess in this way. Seeing them in an aircraft hanger with scissor lift and water bags is an interesting thing to watch.

Your 27Kg panel seems to be a non-issue - but is that 200Kg a total support capacity for the entire thing, or just on each length of tube?

[kerry davies]

A word of caution; there is far too little information for anyone on an open internet forum to make any kind of guess at an answer to this. Brian and Stuart are exactly right, we can't tell you but the installer/designer might be able to. Failing that it needs examination in situ by a structural engineer.

This is life safety critical stuff and as the warning on the Safety thread says; If in doubt, consult a qualified professional.

[Jivemaster]

Ask the right questions, in detail, and in writing. 200Kilos wouldn't hang the cable in most shows or venues.