No Longer A Member 210514 Posted March 6, 2008 Share Posted March 6, 2008 Hi, I'm looking for some rigging advice if poss please! I've been asked by someone to construct a ground supported "box" truss which has two sides of 18m spans, and 2 sides 7m span with a centre 18m span. approx 3.5/4m high. The truss needs to be able to support approx 45 x 1k fresnels evenly distributed plus TRS. I think the self-weight of the truss might be more of an issue. Does anyone have any reccomendations on appropriate Truss to use which is strong enough to have an 18m span only supported by an upright at either end? Also, this is gonna weigh a lot... so if anyone has any suggestions on how to get the structure 4 m in the air, I'd be very grateful. The venue is an art gallery, so not particularly well technically equiped, and apparently has no flying points... Thanks! Link to comment Share on other sites More sharing options...
adamharman Posted March 6, 2008 Share Posted March 6, 2008 Assuming you're hiring the truss in, I'd start by telling the hire company what you want to do with it. They may be able to advise you, or point you in the direction of somebody who can. It probably is achievable using a large square truss, but it's going to be big, heavy and expensive. I wouldn't like to try getting it up there without some sort of proper ground support system and chain hoists. I suspect the total weight will be too much for the smaller truss lifts. Could you not persuade them that to put legs in the centre of the 18m span would be a better idea? Bending moment (and therefore the stress in the truss) is proportional to the square of the span so, roughy speaking, half the span = quarter of the stress = much smaller truss. On a different subject, if the venue is poorly equipped, do they have sufficient power for 45k of lighting? Link to comment Share on other sites More sharing options...
No Longer A Member 210514 Posted March 6, 2008 Author Share Posted March 6, 2008 Assuming you're hiring the truss in, I'd start by telling the hire company what you want to do with it. They may be able to advise you, or point you in the direction of somebody who can. It probably is achievable using a large square truss, but it's going to be big, heavy and expensive. I wouldn't like to try getting it up there without some sort of proper ground support system and chain hoists. I suspect the total weight will be too much for the smaller truss lifts. Could you not persuade them that to put legs in the centre of the 18m span would be a better idea? Bending moment (and therefore the stress in the truss) is proportional to the square of the span so, roughy speaking, half the span = quarter of the stress = much smaller truss. On a different subject, if the venue is poorly equipped, do they have sufficient power for 45k of lighting? Power wise, yes - I have been promised a 125A 3P so hopefully that'll do the trick. I would much prefer to have a central leg, but the designer is adamant that he doesn't want to impair any audience view... Can anyone reccomend a hire company that stock large square truss...? Thanks Link to comment Share on other sites More sharing options...
trussmonkey Posted March 6, 2008 Share Posted March 6, 2008 first you said you wanted a groun support truss then you mentioned flying it etc. which is it as the two are very different. a ground supported truss would not need any flying points. as for which truss you need thomas supertruss 52cm square over a 18m span has a maximum unifform loading of 1000kgs more than enough for your lights but it will deflect a little under its own weight. I would reccomend on the long sides adding an extra leg to take the belly out of it. tm Link to comment Share on other sites More sharing options...
No Longer A Member 210514 Posted March 6, 2008 Author Share Posted March 6, 2008 first you said you wanted a groun support truss then you mentioned flying it etc. which is it as the two are very different. a ground supported truss would not need any flying points.Hi Tm, Thanks for the reply, I would prefer to be able to fly the entire structure, but as there are no suitable flying points in the venue, it has to be ground supported. Do you have any reccomendations for raising the structure up the legs? Chain hoists etc... thanks Nick Link to comment Share on other sites More sharing options...
Ynot Posted March 6, 2008 Share Posted March 6, 2008 Hmmm... Personally, though I have limited experience with truss, I'm using general logic & physical principles here, I'd be tempted to tell the designer to back off and think a little more carefully. 18 metres is a HECK of a span in anyone's money - and no matter what you build it out of, it's almost certainly going to sag in the middle. OK some of the heavier duty truss MAY support the weight better than standard kit, but you're going to be paying significantly more to hire the bigger units. The designer is going to have to make a trade-off on a number of issues:Single span = almost guaranteed belly down on the long span and a lot of stress on the structure. Also higher cost.Mid-supported span = tidier looking truss, sturdier construction and cheaper overall. Link to comment Share on other sites More sharing options...
dunk_1984 Posted March 6, 2008 Share Posted March 6, 2008 Do you have any recommendation's for raising the structure up the legs? Chain hoists etc... Unfortunately you answer this yourself when you say there are no suitable flying points. If there are no fly points, no way to attach chain hoists. You will just have to put it to the client, BIG truss, a middle leg (or 2) or find a way to fly the rig. To get it up... Winch stands then replace with truss legs, or build truss then hang lights after it's in the air. Link to comment Share on other sites More sharing options...
danjshelton Posted March 6, 2008 Share Posted March 6, 2008 Do you have any recommendation's for raising the structure up the legs? Chain hoists etc... Unfortunately you answer this yourself when you say there are no suitable flying points. If there are no fly points, no way to attach chain hoists. Hi, I think that when Nick was talking about chain hoists he isn't talking about flying the structure (as he already knows and has stated that there is no flying in the venue), I believe that he is talking about if anybody can recommend a system to get the ground supported structure in the air, and one of these ways can be a self climbing ground support (which will incorporate the use of chain hoists (of some sort!)). Of course I could have completely misunderstood the topic! Cheers Dan Link to comment Share on other sites More sharing options...
trussmonkey Posted March 6, 2008 Share Posted March 6, 2008 as long as you put a third leg I the long span then what you propose is absolutly fine. as stated you could either use a self cllimbing ground support. where chain hoists are fitted to the legs of the truss and it climbs the legs. or you could use several superlifts (prob 6 ) to lift the box then you would add truss as the box gets higher until you reach the desired trim height. most suppliers dont differciate significantly between 52cm and 30cm truss. drop me a line and ill see if my company can help. Link to comment Share on other sites More sharing options...
Steve Cavill Posted March 6, 2008 Share Posted March 6, 2008 Get hold of Grant @ AC Lighting, and ask about the Litec Libera Truss. Its heavy duty stuff and will cope with 18m spans. Its not going to be the best looking solution, but 18m is a hell of a long way for a single span! Link to comment Share on other sites More sharing options...
Jivemaster Posted March 6, 2008 Share Posted March 6, 2008 Do a sketch of the truss you and the designer want, then ask your chosen hirer for a fully calculated truss system to do the job. Preferably get a assembly method and rigging method from them too. If they don't have the skill or inclination to do this for a charge, then move onto someone who does. If you do not have the full rigging design skills you need to buy them in or run un-necessary risks. Link to comment Share on other sites More sharing options...
Seano Posted March 6, 2008 Share Posted March 6, 2008 Can anyone reccomend a hire company that stock large square truss...? UK Rigging, Star Events Group and Summit Steel would all be able to do this, and all would be happy to offer you advice. There are a fair few other companies out there who could do it, but these are the first ones I'd be talking to about a project like this. 18m is a hell of a long way for a single span!Its a bit longer than average, but not that long, particularly as the OP isn't looking for an enormous load capacity. Total Fabs, Slick and Thomas all make standard trusses that will cope with an 18m span quite happily. If you do not have the full rigging design skills you need to buy them in or run un-necessary risks.Agreed. You (the op) don't mention how long the run is, a self-climbing ground support would undoubtedly be the way to go for a short run, for a longer run you may find a simple freestanding truss structure less expensive (more troublesome and costly to erect -vs- lower hire costs throughout the run). Again this is something you'd be better off discussing with a hire company than asking about on here. Best of luck.Seanx Link to comment Share on other sites More sharing options...
dave singleton Posted March 6, 2008 Share Posted March 6, 2008 I know Unusual Rigging may well be able to help as I have seen them do similar distances before. A custom designed hire solution may be your only answer. I can't promise it will be pretty but that distance IS possible with the weight you intend. Link to comment Share on other sites More sharing options...
Roderick Posted March 6, 2008 Share Posted March 6, 2008 Another thing you want to check is floor loading!It is going to be a heavy structure supported at 4 points, a lot of weight on a very small area. Link to comment Share on other sites More sharing options...
No Longer A Member 210514 Posted March 6, 2008 Author Share Posted March 6, 2008 Another thing you want to check is floor loading!It is going to be a heavy structure supported at 4 points, a lot of weight on a very small area. Very good point... TBH I hadn't even thought about what would be supporting the self supporting truss...! Thanks Link to comment Share on other sites More sharing options...
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