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longest length between couplers with box truss


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looking to fly some box truss using 2 couplers /bolts attached to ceiling beams at each end

length of this truss is 7m

load on the truss is just under 100kg


could truss take this load without snapping in the middle or do I need to get the drill out and dead hang the middle?






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We really hate these kinds of posts because in most cases, the poster has determined that this is what they wish to do, and simply want corroboration of their decision. The truth is we simply cannot.

The main reasons are that you haven't given us any details of the truss? The manufacturers have all the engineering information that can be used to determine if the structure is safe. 100Kg load could be safe or maybe not. Where is it? One huge load in the centre, or evenly distributed? So many questions, that without information we just cannot answer.


What will happen is that people will jump in and tell you that if you don't know, you shouldn't be doing it - which while true, isn't that helpful.


Tell us what it is, provide us with some drawings, and detailed loading information - then people might be able to pick up points you've not thought about.


We do this so often, we can almost predict what happens. Some people will just suggest you don't do it - which is in reality the only answer a complete stranger on a forum would sensibly say.


After all, if we all say it's fine - and then it fails (keeping in mind the death reported on this forum very recently when there was a failure) what will you say in court? "but your honour, I was told it was safe" - Who by? No idea!


See the problem.




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I see your point ... I wasnt looking for a definitive answers just suggestions


I havent chosen the truss... im wondering whether there is truss out there strong enough to do this with only 2 anchor points


the load is 2par 64s 1x 30kg head 2par 64s 1x 30kg head (centre) 2par 64s 1x 30kg head 2par 64s

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There are a few things about your plan that worry me a bit. Firstly, you're talking about chucking up some fairly heavily loaded truss in the biggest nightclub in the city. You then go on to talk about just using "2 couplers/bolts at either end"


There are a lot of people in and around Derby that'd be able to come down and advise on the situation. I'm sure someone who's flown truss in nightclubs before will be able to give you a hand.


It's better to be over cautious than to be picking up the pieces when/if it comes down over a few hundred punters.


You've got truss in the venue already, I'd be looking at going for the same stuff.



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The real problem with doing this kind of thing is what Josh touched on.


Let's say you choose some truss that over 7m, with your 100KG hanging off it only droops in the middle by an amount small enough to be within the manufacturers deform spec. Your support at either end needs to be able to safely manage the load AND the truss. Can you determine that the fixings and whatever you are supporting it on can manage to keep the thing up? I'm happy myself with understanding the specs, but I'm not an engineer. I work with some quite often, and they always determine the suspension system, and carry out the installation of the parts that need knowledge and skill to put together. They're happy with me hanging truss that I have selected from their suspension system - usually just checking what I'm buying. Sometimes I find the spacing between drops is less and the steel wire rope thinner - other times there will be less drops, and I'll have to have stronger truss to carry the loads. On a few of these, the manufacturers published material didn't quite fit - so I sent the engineering drawings of the suspension system available and details of what I wanted to hang on the truss to the manufacturer and they suggested the next range up.


I am happy working within my limits, and when I don't know, I know who to ask. I do not have the correct skill set to look at a wall, a ceiling or a steel beam and know what I can hang off it - that's why structural engineers earn their pay (and carry excellent professional indemnity insurance).

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As everyone else has stated there are too many unknowns for a definitive answer from any of us.


However, as a starting point you might be interested to look at Thomas GP 30.5 Truss purely as an example of load tables, where it talks about length, suspension, centre point loads, uniformly distributed loads etc. etc.


While you can see from reading the tables that the truss is capable of large amounts of weight over long spans, this of course means nothing if you A) you don't really what your doing with it. B) Don't really know how to hang it. C) You don't know if the suspension points are rated to take it. D) many, many other factors.


Like I say, might be a good starting point and something to think about.

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