Pete Alcock Posted February 14, 2006 Share Posted February 14, 2006 I have a project where a 7m span of truss is needed. To hang 2 speakers (32kg Total), 8 Par56s, a couple of disco FX projectors and an LCD projector (and cable of course). The ends will be very securely fixed to the walls and there is no loading issue there. Now the load ratings for all the various triangular truss makes are well publicised, but I really wanted to use ladder truss - partly look, but also economy. Penn or Prolyte maybe. Anyone get any charts for ladder truss or otherwise could indicate whether "yes, you're well inside" or "forget it - use tri-truss". Thanks, Pete. Link to comment Share on other sites More sharing options...
klimov Posted February 15, 2006 Share Posted February 15, 2006 INow the load ratings for all the various triangular truss makes are well publicised, but I really wanted to use ladder truss - partly look, but also economy. Penn or Prolyte maybe. Anyone get any charts for ladder truss or otherwise could indicate whether "yes, you're well inside" or "forget it - use tri-truss". Thanks, Prolyte has charts of ladder type trusses published on the website. The ones you need are x30l, h30l or, probably the best choice, h40l. The biggest span covered is 6m, thou.It seems possible at the first sight, but to be sure more info on projector's weight and distributed load of pars needtd since we are pretty close to the limits here. Also it's important where the speakers are supposed to be redarding hanging points and this is even more important if there is not going to be any.. Link to comment Share on other sites More sharing options...
paulears Posted February 15, 2006 Share Posted February 15, 2006 one thing - even if the rating charts show it is safe, the span is very large for a bit of ladder truss - you are going to have at least 2 joins, and each one is a problem. On high quality 3 or 4 chord truss, the spigot design pulls the ends tight, in other designs more common in 2 chord ladder, there is always a little play. This means that even without any substantial loading, the damn thing will droop down in the middle, looking unsafe, even if not actually, unsafe. Can you not get any centre support at all? Link to comment Share on other sites More sharing options...
Pete Alcock Posted February 15, 2006 Author Share Posted February 15, 2006 Paul, Thanks for that. I realise it's a long span for ladder truss. Probably not a goer. Unfortunately there's no possibility of ceiling support, as the (Church hall) ceiling is a 30's curved wooden rafters affair. Arches are not great at taking loads, and I've been advised against any sort of ceiling suspension by a structural engineer. My original proposal was for a ground supported "box" of lightweight truss, but that was rejected on the grounds that youngsters in the playgroup might climb up it(!). Back to the drawing board, and tri-truss I think. Pete. Link to comment Share on other sites More sharing options...
djw1981 Posted February 16, 2006 Share Posted February 16, 2006 If it is an install then surely your box truss idea would work if you then put padding (like goes round rugby posts) or a wooden box around the truss and fasten it to the wall?up to a height of say 5ft? Link to comment Share on other sites More sharing options...
Pete Alcock Posted February 16, 2006 Author Share Posted February 16, 2006 David, I suggested that, but then the older members thought it would look unsightly, and raised the issue that truss "legs" near the edge of the hall could be an inconvenience to wheelchair folks. Basically has to be fixed to the walls, hence the wopping span. These installation jobs are rarely straightforward! PLA. Link to comment Share on other sites More sharing options...
david.elsbury Posted February 16, 2006 Share Posted February 16, 2006 What about something like the following:(attempt at ASCII drawing follows)|\ /| | \ / | | \ / | | \ / | | \ / | | \ / | |===========================| As if you are able to have points on the sides, where you can fix to, perhaps you can go with a similar thing to a suspension bridge? David Link to comment Share on other sites More sharing options...
Pete Posted February 16, 2006 Share Posted February 16, 2006 At the risk of being frowned at... How about some ex rental lightbeam? Link to comment Share on other sites More sharing options...
Kaboom25 Posted February 18, 2006 Share Posted February 18, 2006 Also bear in mind that if using truss that is bolted straight onto two vertical walls at either end it needs to fit exactly. Couple this with the issue that when you start putting load onto the truss it will deflect and apply more force onto the top mounting than the bottom one - ie the top one will be getting pulled out of the wall (tensile force) and the bottom one will be getting pushed into the wall (compression force). You'll need to take this into account when designing the anchors to hold it all up. My advice would be some kind of shelf frame bolted into the wall then secure the truss on top and then use another mounting at the top to stop it rotating. Cant really say anything more without seeing the place. ttfnCC Oh in terms of truss have a look at Milos stuff. cheaper than prolyte with similar specs. it may mean that you can afford a 7m length of box or tri after all. Link to comment Share on other sites More sharing options...
Duncan Wood Posted February 20, 2006 Share Posted February 20, 2006 My original proposal was for a ground supported "box" of lightweight truss, but that was rejected on the grounds that youngsters in the playgroup might climb up it(!).You could "clad" the uprights with smooth tube over them Link to comment Share on other sites More sharing options...
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