Another case of questionable rigging?

S

Simon Coffin

Sophomore
Mar 2, 2011
133
1
18
State College, PA
www.medianengineering.com
While cruising Soundbroker.com I came across an ad for a Soundbridge Xyon rig. Its in all capitals, the spelling and grammar are iffy and the stated coverage makes no sense. Fair enough, some people can't write. Apparently some people can't fly line arrays either. I think this whole thing is hanging from two span sets? Each cabinet weighs 86lbs, there are 10 of them for 860lbs, plus another 50lb for the bumper and we have a total hang of 910lbs. What's the wll of those span sets? And shouldn't there be a safety cable as well?
Flown Soundbridge Xyon.jpg
Thoughts?

Ciao
Simon
 
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Re: Another case of questionable rigging?

Simon Coffin said:
While cruising Soundbroker.com I came across an ad for a Soundbridge Xyon rig. Its in all capitals, the spelling and grammar are iffy and the stated coverage makes no sense. Fair enough, some people can't write. But the rigging of the flown array is also scary.

View attachment 9493
Thoughts?

Ciao
Simon
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"What's right with this picture?"
 
Re: Another case of questionable rigging?

Greg Cameron said:
Crap. The rigging looks as good as the sound quality of those boxes.
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I was wondering how long it would take for someone to corrolate sound quality and rigging quality. The boxes themselves appear to have reasonable intercabinet rigging and a sizable bumper frame at the top, but how its hung from the trussing is beyond ignorant.
 
Re: Another case of questionable rigging?

Simon Coffin said:
I think this whole thing is hanging from two span sets? Each cabinet weighs 86lbs, there are 10 of them for 860lbs, plus another 50lb for the bumper and we have a total hang of 910lbs. What's the wll of those span sets? And shouldn't there be a safety cable as well?
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Simon,

Assuming two real purple Spansets in good condition, each choked with equal load, the WLL is 4240 pounds. Spanset uses a 5/1 safety factor, minimum breaking strength should not be less than 21,200 pounds. Some portion of the truss would likely fail before the Spansets.

Spansets may not be legal for support in some jurisdictions as polyester can melt and burn, if you see speakers on fire supported by Spansets, stand well clear of the fall zone ;^).

Art
 

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Re: Another case of questionable rigging?

But many people forget the angle of the load also matters. There is more to the tension story than just the dead weights.

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Re: Another case of questionable rigging?

Art Welter said:
Simon,

Assuming two real purple Spansets in good condition, each choked with equal load, the WLL is 4240 pounds. Spanset uses a 5/1 safety factor, minimum breaking strength should not be less than 21,200 pounds. Some portion of the truss would likely fail before the Spansets.

Spansets may not be legal for support in some jurisdictions as polyester can melt and burn, if you see speakers on fire supported by Spansets, stand well clear of the fall zone ;^).

Art
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How resistant to UV are spansets? Most of those synthetics can broken down over time. So, how much sunlight have they seen?
 
Re: Another case of questionable rigging?

frank kayser said:
How resistant to UV are spansets? Most of those synthetics can broken down over time. So, how much sunlight have they seen?
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Judging by the color of the purple casing the Spansets in the OP, they don't look like they have seen too much sunlight. The casing protects the load bearing strands from UV and physical damage, if it shows cuts or UV fading the Spanset should be retired from rigging use. UV exposure really varies, up here at 6000 feet everything, whether organic or synthetic, goes bad much faster than at sea level.

I have used faded, torn to crap synthetics to pull vehicles from ditches, remove dead trees and drag large metal objects around, though I'd never use them for rigging where a failure would cause bodily harm, have been surprised how much they still can take before failure.
 
Re: Another case of questionable rigging?

Tim McCulloch said:
The significant issue is WHERE the round slings apply the load to the truss. I'll give you a hint, the method in the picture is unforgivably wrong.
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Well that answers that question. I don't know enough about rigging to really have a certain opinion of most of it, besides that it simply looks dangerous half of the time it's posted.

Didn't you suggest a book on it to someone on this forum a while back? I should probably order a copy.
 
Re: Another case of questionable rigging?

Max Warasila said:
Well that answers that question. I don't know enough about rigging to really have a certain opinion of most of it, besides that it simply looks dangerous half of the time it's posted.

Didn't you suggest a book on it to someone on this forum a while back? I should probably order a copy.
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The definitive reference is "Entertainment Rigging" by Harry Donovan
Entertainment Rigging: Harry Donovan: 9780972338110: Amazon.com: Books

The next step up is a structural engineering curriculum, which includes such topics as statics, dynamics, strength of materials, etc. Most jurisdictions will let you do almost anything with rigging provided you can get a qualified (licensed) engineer to approve it.
 
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Re: Another case of questionable rigging?

Tim McCulloch said:
The significant issue is WHERE the round slings apply the load to the truss. I'll give you a hint, the method in the picture is unforgivably wrong.
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I'm not a rigger but for the sake of learning I'm going to go out on a limb and assume you mean the fact that the speakers are hung from the bottom of the truss. Shouldn't the hang be from the top of the truss?

Also looking elsewhere in the picture, I notice the black spansets that attach the lift line are choked around the individual rails of the truss. Is this considered acceptable? The rigs I have seen in the past, the spanset is long enough to go all the way around both bottom rails.
 
Re: Another case of questionable rigging?

The goal of rigging is to defy gravity for a relatively short amount of time, and not kill or injure anyone or anything in the process.

One of the basic concepts of rigging is that you want to apply a load so it will compress the "beam" rather than putting it into tension. That's the reason you would attach the load to the TOP chords of the truss, compression. In the picture you see the bottom truss chords in tension, and note that at the node (where the 2 diagonal "laces" form an apex, up or down) the lacing is all that holds the load, whereas if you load the truss from the top chords the lacing spreads the load to the bottom chords. This is dangerous and the roof technician should not have allowed it.

Also note that the speaker array is connected directly to the horizontal truss. The array should have its own hoist(s) rigged from the horizontal. It appears this is a sound bay that is part of a roof system (look in the upper left corner). That means an asymmetrical and unbalanced lift; it means that if the PA needs trimmed in due to weather the whole roof comes down with it. I won't say this is patently unsafe, but I will say we don't do things that way in our shop.

Shameless plug: check out the Event Safety Alliance. Really.

Shameless plug #2: get the Donovan book. Double really. Reading it won't make you a rigger but you'll be able to intelligently discuss your particular needs with a rigger. You'll be able to identify some dodgy practices and poor materials choices. Hopefully you'll never see those on *your* gigs. :)
 
Re: Another case of questionable rigging?

Depends on the manufactures design specs. Some allow using truss in tension rather than compression. Others don't allow it. Honestly it just looks tacky not so much gonna fail. Thats as far as I'd go with judging until I knew exact situation and exact manufacture of truss.
 
Re: Another case of questionable rigging?

Jordan Lahr said:
Depends on the manufactures design specs. Some allow using truss in tension rather than compression. Others don't allow it. Honestly it just looks tacky not so much gonna fail. Thats as far as I'd go with judging until I knew exact situation and exact manufacture of truss.
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Yes, but you can always safely load a truss in compression, but not the other way around. Aside from using the sound bay to do a dead lift, all they'd need is a pair of 3' spansets and shackles to fix this.
 
Re: Another case of questionable rigging?

Tim McCulloch said:
The goal of rigging is to defy gravity for a relatively short amount of time, and not kill or injure anyone or anything in the process.

One of the basic concepts of rigging is that you want to apply a load so it will compress the "beam" rather than putting it into tension. That's the reason you would attach the load to the TOP chords of the truss, compression. In the picture you see the bottom truss chords in tension, and note that at the node (where the 2 diagonal "laces" form an apex, up or down) the lacing is all that holds the load, whereas if you load the truss from the top chords the lacing spreads the load to the bottom chords. This is dangerous and the roof technician should not have allowed it.

Also note that the speaker array is connected directly to the horizontal truss. The array should have its own hoist(s) rigged from the horizontal. It appears this is a sound bay that is part of a roof system (look in the upper left corner). That means an asymmetrical and unbalanced lift; it means that if the PA needs trimmed in due to weather the whole roof comes down with it. I won't say this is patently unsafe, but I will say we don't do things that way in our shop.

Shameless plug: check out the Event Safety Alliance. Really.

Shameless plug #2: get the Donovan book. Double really. Reading it won't make you a rigger but you'll be able to intelligently discuss your particular needs with a rigger. You'll be able to identify some dodgy practices and poor materials choices. Hopefully you'll never see those on *your* gigs. :)
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This has to be far and away one of the most informative and productive posts I've ever read in any of our innumerable "trash the rigger" threads. I want to publicly and personally thank you for it.
 
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