Light fixture safety cables

In short: no. No no no no.
I have never seen a safety cable rated for overhead lifting. Many do have a published safe working load (WLL) but they virtually all come with disclaimers stating they are only to be used for their intended purpose.
For example from ETC:
Disclaimer: The ETC Safety cable P/N 7060A1022, is to be used as a safety device for ETC lighting fixtures only. It should not be used for rigging or lifting any items or people and should not be used under tension.
 
Someone texted me the other day asking what the WLL of a lighting safety was. I had 2 answers.

1) The legal answer is one lighting fixture.
2) In my destructive testing the clip fails before the wire rope and that force is more than one lighting fixture, even the big wiggly ones.
 
I totally agree with that main use of a lighting safety and only use it for that purpose but to debate
" rules that are acceptable to be broken "

I read tests have shown that lighting safetys on a straight pull will break ~ 1500lbs (5:1 ~300lbs)
and in basket it breaks at ~2900lbs (5:1 ~590lbs)

So if the object to be hung is within those numbers can it be argued that it is okay to to hang of safetys.
 
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Haven't we agreed that "overhead lifting" applies to things that move?

I agree, though might add "vertically". I don't consider a dead hung curtain track to be overhead lifting by virtue of the movement. Any load that is raised and lowered at anytime over heads of people.

I have made a case that a load that is moved vertically is not overhead lifting when the space under it is not occupiable. An acoustic banner where people are prevented from being under it.
 
Someone texted me the other day asking what the WLL of a lighting safety was. I had 2 answers.

1) The legal answer is one lighting fixture.
2) In my destructive testing the clip fails before the wire rope and that force is more than one lighting fixture, even the big wiggly ones.

Putting on my stupid hat here. I don’t think I have seen this discussed.

If a clamp failed catastrophically, it seems there would be a shock load on the safety that could apply more force than the clip could handle.

Is there any data that supports a double wrap of the safety for heavier fixtures? If so is there a definition of heavy enough to double wrap?

By double wrap I mean go twice around the pipe/yoke so the shock load would be reduced.
 
Here's what I teach:
For conventionals, single wrap, enough slack to focus any direction.
For movers, double wrap, and/or as little slack as is practical, to shorten shock load distance.
A twelve pound Leko falling one foot may not exert much shock load, but a fifty pound mover might.
While not proud of it, I've used lighting safeties to hang fast-fold screens, provided they're in good condition and the clips are working properly. Beats tieline. Or zip ties.
 
Here's what I teach:
For conventionals, single wrap, enough slack to focus any direction.
For movers, double wrap, and/or as little slack as is practical, to shorten shock load distance.
A twelve pound Leko falling one foot may not exert much shock load, but a fifty pound mover might.
While not proud of it, I've used lighting safeties to hang fast-fold screens, provided they're in good condition and the clips are working properly. Beats tieline. Or zip ties.

Properly swaged aircraft with verlocks?


I noticed lighting safetys are swaged differntly than normally would on aircraft cables.
Reason?
 
Putting on my stupid hat here. I don’t think I have seen this discussed.

If a clamp failed catastrophically, it seems there would be a shock load on the safety that could apply more force than the clip could handle.

Is there any data that supports a double wrap of the safety for heavier fixtures? If so is there a definition of heavy enough to double wrap?

By double wrap I mean go twice around the pipe/yoke so the shock load would be reduced.

A safety that is in a loop already has double the capacity that if it was in a strait line.

Properly swaged aircraft with verlocks?


I noticed lighting safetys are swaged differntly than normally would on aircraft cables.
Reason?

the tool used to make the compression is a wide jaw that requires only one compression. more like what you see on a flemish eye. thats why it looks different.

I totally agree with that main use of a lighting safety and only use it for that purpose but to debate
" rules that are acceptable to be broken "

I read tests have shown that lighting safetys on a straight pull will break ~ 1500lbs (5:1 ~300lbs)
and in basket it breaks at ~2900lbs (5:1 ~590lbs)

So if the object to be hung is within those numbers can it be argued that it is okay to to hang of safetys.

1/8" wire rope has a MBS of 2000lbs. I break a lot of it, domestic and imported. Almost all of the time it fails over the MBS. For a lighting safety it's the clip that is the issue. Want the ultimate lighting safety? replace the clip with a shackle.
 
For argument of right wrong when see someone use lighting safetys on jobsite. It isnt wrong if within load capacity . - It is " perfectly and acceptable rule to be broken "
 
How to calculate shockload?

It's not too difficult IF you know the weight (fairly easy to determine), the distance it falls (fairly easy to determine), and the stopping distance (tougher to determine - not impossible but probably not info that you have at your fingertips either).
For a fixture that falls onto a safety cable the stopping distance is very small, so more shock load than you might think.
 
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Sure. Imagine if the safety cable was a giant rubber band that could stretch out four or five feet before the fixture gradually came to a complete stop. Less shock, no? Same principle as shock-absorbing fall protection.

Um, @JAC, I think you're missing an important point about fall arrest lanyards - they're sewn with "shock loops" (for lack of a technically correct term) that break and increase the length of the lanyard, thereby absorbing energy and trying to lessen the eventual shock of the 'arrest' from the harness wearer.
A safety cable, as you might note, is simply a piece of wire rope. When the end of the travel is reached the load is arrested and all force is taken immediately by the connection points.
So, since F=ma, and our mass is constant, the only way to lessen force is to reduce acceleration. Acceleration is reduced by reducing the distance traveled (you can't go as fast from zero traveling 10 feet as you can traveling 100 feet) so the shorter you can make the travel of the fixture falling the less your shock load will be. The analog to this in fall arrest would be the retractable lanyards which lock travel after an inch or two. They don't try to brake and slow the travel over 6 feet, they lock within inches. less travel = less force.
 
Longer the free fall distance the heavier the object?

Example A 5/ 8 nut falling from 10ft vs 50t.
50 ft fall will generate more force . ..

Am i thinking completely wrong here?
 

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