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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Lighting Forum => Topic started by: Bradford "BJ" James on December 15, 2018, 02:57:10 PM
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I am renting out some ST-132's to a customer. They're planning on using 4 sticks of 6' Global 12" box truss to hang some lights. 24' span. The lifts are adequate, but I'd rather see them using 3x 8'(...and also would prefer to rent that to them). Any dangers using the 6' sections other than a little more deflection? The weight will be within the rated maximum for the ST-132's.
Cheers. BJ
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How much weight are they hanging?
How is it distributed?
Is it within the rating of the truss?
Admittedly, having a joint at the center is not the best scenario.
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It all depends on the loading, in my somewhat limited experience. I have 2 m and 1 m segments of Global Truss, and have gone out to span 13 meters (43') for front lighting presentations in a meeting room, without problems. 2 meter (6.5') lengths of truss are easier to deal with than 3 m/10' sticks for lounge level folks like me and my rental clients. YMMV.
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4 x 6' sticks of F34 truss weigh 124lbs alone, another 12 lbs for the truss adapters, another bit for pins and such. The ST132 is 220lbs each, so 440lbs total. That means remaining capacity of 300lbs roughly at best when evenly spaced (e.g. not heavier over one lift). Are you certain that this customer is going to be able to rig this all appropriately and within capacity? 300lbs disappears really quickly depending on the light fixtures and cabling used.
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I am renting out some ST-132's to a customer. They're planning on using 4 sticks of 6' Global 12" box truss to hang some lights. 24' span. The lifts are adequate, but I'd rather see them using 3x 8'(...and also would prefer to rent that to them). Any dangers using the 6' sections other than a little more deflection? The weight will be within the rated maximum for the ST-132's.
Cheers. BJ
We regularly use three sections of 2m (6.6') F33 triangle truss over two ST-132s and adaptors. Let's see, the weight is 3 Chauvet movers (27 lbs.), 4 Blizzard Q12s (24 lbs.) eight Blizzard Rokspots (16 lbs.) and the various cords, clamps and bar hangers don't add more than another 35 lb. so total hang weight is around 100 lbs., excluding the truss and adapters. All symmetrical, so no added weight on one end. We have plenty of capacity by the specs and from the feel after it is assembled, and wouldn't hesitate to add another stick if it was as lightly loaded and symmetrical as the remainder of the truss. Especially if all the pins and safeties are correctly used.
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I'm with Dave that having the joint in the center isn't ideal. But for those crank stands max weight (440lbs) when compared to an 8m (26ft) span weight capacity of over 1100lbs I seriously doubt it's an issue. One sec while I do some napkin math.
When in doubt email Global Truss' engineers; they've signed off (verbally) on designs for me.
http://www.globaltruss.com/downloads/Load%20&%20Deflection%20Charts.pdf