Rigging guys... a question

[Bradfo69]

I am getting ready to potentially buy some trussing. It's not exactly what I want but, it's what I can afford right now and, I have some parts already so, I sort of need to stick with what's been started since I've got about $500 into it already.

My question is, how much weight can this theoretically support safely.

This is using Global Truss parts. It's two ST132 crank tripod stands rated for a 220lb vertical lift. The cross bar will consist of F-32 I-Beam. There will be 6 pieces. The two in the center are the 8.2 foot long sections. Then, working out from there it will be two 1.6 foot vertical "T"'s which are going to hold a baseplate that either a projector or moving head could sit on top of. Then, extending from the T to the tripods will be 6.5 foot sections.

Overall length I guess is around 32 feet. According to Global Truss - assuming I read correctly - the rated load for a section of I beam truss that long is around - we'll say - about 900 pounds with about a 2.2 inch center deflection.

Now, I know there are calculations for de-rating and percentages you should be under... yadda... yadda... so, what I'm trying to estimate is just how much I can hang or place on this set up. I'm leaning towards perhaps 4 Martin SCX600's at about 30 pounds each, two or three lasers between 30-40 pounds each and maybe a couple Chauvet Intimidator Beam 350 moving heads that I think are perhaps 20 pounds or so.

Not my ideal setup but can buy me a year or two until I can get box truss and stands with outriggers or... just use box truss for the uprights as well, which I know will limit my height to a fixed amount and always require a ladder.

See illustration: Thanks!

[Mlenox]

Invest in real truss. Tomcat is pretty much the industry standard in the US. 30' is the maximum distance between two points. and if you're using global truss, you'll have deflection with just the weight of the truss. L-16 crank stands are rated to 500 pounds each. I own 6 and love them. Try usedlighting.com if you're on a budget.

[Bradfo69]

I sorta need to stick with Global since that's what I have already. I don't tour with the stuff so, it's not like I need a top of the line arena show grade but, I'm not going cheap like On Stage or Odessey. I have a large company (Light Action) that builds the stuff about 10 minutes from my home and have thought about talking with them since it would save shipping. Just haven't gotten over there to snoop around.

(I do want to look at the crank stands you mentioned though.)

[The_Doctor]

I'm not sure how similar truss is to square tube, but playing with this thing might help get some gaugeing of it:
http://metalgeek.com/static/deflection.php

(I used it to work out what size of stainless square tube at 6m length was needed to hold six 80W solar panels safely when it was supported at each end and nowhere else.)

[norty303]

Hi Brad

I estimate 32 ft to be about 9m which is too long to use F32 (or any ladder truss) supported between a pair of stands. Global only rate up to 4m in this way, but 6m is ok I've found.
The ratings for longer spans are when the truss is suspended with supports every 1m on the compression chord. Check the Global China site for better load tables, the US site seems to pick the best ratings but doesn't state the 1m support of the compression chord, which I find dodgy.

The big issue you will have is actually not the loading, but the fact the truss will start to deflect forward or backward, as it basically has no strength in that axis. I'm talking from experience of an 8m span here, that started oscillating back and forth under very minor shocks through traffic on the stage.

There is nothing wrong at all with Global Truss, it is properly rated and works well when used correctly, but you will really want to be using F33 or F34 for a 32ft span.

I have quite a bit of F32 and F33, and it is compatible with a few other popular brands over here.

The ST132 are also good stands and fantastic value for money. If you aren't going to tour them hard then they will also be just fine.

I'm just uploading a video showing an F33 8m span on ST132 lifts that was near the lift load limit, but nowhere near the truss limit, and you'll see hardly any deflection

http://www.youtube.com/watch?v=HChmJ...ature=youtu.be

[Bradfo69]

Thanks. I was a little afraid of that.

I made the possible mistake of buying some brand new Global truss parts from a DJ friend of mine and found what I have to be useless without buying more and, trying to find the most cost effective solution to make use of it. Your video illustrates basically what I want to do and, as I said in the OP, I really want the ST157 stands (think that's the number) someday, with the outrigger style legs. They lift 330 pounds and can go up to 15' but, they're also $1100 more money. They weigh more than I do and the legs are a lot longer than what I may have room for at 84". Very similar to the L-16 mentioned above. Plus, ideally I'd like the box truss (F-34 I think) but again, to span that distance it's another $1700 and doesn't use a thing from the $500 I've already spent. I know I'm going to have to bite the bullet and spend decent money for this stuff but, I don't use it enough to recoup the investment unfortunately. It probably holds resale value if well cared for though.

I do think the ST132's are going to be adequate and may still go ahead and get a pair and, then have to wait on the truss for awhile. I hate to wait....

[norty303]

If you were able to use a 3rd ST132 in the centre of the span you'd be able to use 32ft of F32. So only a little more expensive than the original plan. Which truss adapters do you have?

[Bradfo69]

I thought about that. That may actually be the solution. Or at least SOME type of center support.

One of the things I am trying to avoid though was having a stand of some sort be directly behind a bride and groom when they are sitting at a head table on stage. It just doesn't look nice from a picture perspective. As it is now, when a wedding has a head table, I only use the lasers in the corners of the room - or at least spread pretty far apart. Our dance floor is positioned directly in front of the stage/head table.

If you look at photo 12 in this gallery: http://www.executivebanquets.com/jessicaanthony.htm you'll see what I have to deal with. I can't have a center projector particularly well with that setup. Truss isn't a much better alternative but, at least it's less obtrusive than a stand positioned directly behind them.

As a side note, those speakers aren't normally there. That's where the ST132's would go. The DJ at this wedding insisted on bringing his own in.

Lighting is a lot easier when they don't have a head table or, when it's positioned somewhere else in the room. Usually then the DJ is on the stage.

Truss adapters? You mean the conical connectors between sections of truss or, the "moose ears" on top of the ST132's for the truss to lay in?

[Bradfo69]

Some of the pics from this gallery show it too:

http://www.executivebanquets.com/jacquelineamner.htm

[norty303]

By truss adapters I mean the bits that go on the top of the lifts that hold the truss. For F32 you need vertical ones, for F33 and F34 you need horizontal ones.
Have you thought about getting a rigger to come and put a couple of points and chain hoists in if it's going to be used regularly? No unsightly stands then