C-Clamps for Moving Lights

[Catwalker]

This may seem like a dumb question, but better safe than sorry, right? So, I want to hang a Chauvet Rogue R2 Spot. I have the brackets that come with the fixture. The C-Clamp says Max 500# on it. The Fixture is under 50#. My math skills would suggest that is sufficient, but are there factors that I have not taken into account? I don't understand rigging to a high standard, and would rather look dumb on the Internet than make a mistake like that.

 

[Les]

Yeah, you're fine. That 500# limit should have a significant safety factor built in, but you're still well within the 5:1 ratio either way. Also if you're using two clamps (which is usual), you've actually got 950# of headroom. There are indeed some kinetic forces involved here, but not enough in this case for it to affect you.

 

[BillConnerFASTC]

It would be interesting to know what Chauvet testing procedure is and what the actual design factor. There is no standard and hardware seems to be labeled anywhere from 1/3 breaking strength to 1/10 or greater. Ford?

 

[Ford]

Well, since you asked....

All of our current moving heads use the same Omega Bracket design. So the brackets are designed with the heaviest fixture in mind. We have a safety factor already figured in on the bracket rating, and as alluded to in the earlier post, most of the fixtures have a greater than 10x safety factor to the listed rating of the bracket.

So... With a 50# fixture with 2 brackets you are at 20:1 to the listed load capacity. Add to that the fact that the brackets are already derated, and you can see that you are actually well in excess of 20:1.

You are totally safe.

If you are subjecting the fixture to forces that will exceed a 20:1 load ratio, you're probably going to rip the head off before you drop it.

 

[Catwalker]

Thanks for the info. As a side note, those fixtures are very impressive. I knew they would be punchy coming in, but it's different seeing it in person!


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[BillConnerFASTC]

Well, since you asked....

All of our current moving heads use the same Omega Bracket design. So the brackets are designed with the heaviest fixture in mind. We have a safety factor already figured in on the bracket rating, and as alluded to in the earlier post, most of the fixtures have a greater than 10x safety factor to the listed rating of the bracket.

So... With a 50# fixture with 2 brackets you are at 20:1 to the listed load capacity. Add to that the fact that the brackets are already derated, and you can see that you are actually well in excess of 20:1.

You are totally safe.

If you are subjecting the fixture to forces that will exceed a 20:1 load ratio, you're probably going to rip the head off before you drop it.

Do you have actual destructive testing data? Sure would be nice to see. The Mega clamp - our spec standard - has been tested and in a vertical load test fails - permanently deforms - over 5000 pounds. With a safe working load of 600 pounds, that's about an easy 8:1 design factor. A manufacturer's safe working load as a factor of the actual load at failure varies too much to rely on it in my experience.

 

[JD]

Just to be clear; I don't think anyone is talking about a generic "C" clamp. (Iron casting without rating, shaped like a C with a threaded bolt and a lock screw.) In case someone in the future happens on this thread, there are some problems associated with generic C clamps.
One, is the lack of rating.
Two, is using such a clamp on a soft metal truss where the bolt can actually deform the metal and cause the clamp to loosen.
Most of these clamps have found their way into the dust-bin of history, but there are still a few around.

 

[techieman33]

Just to be clear; I don't think anyone is talking about a generic "C" clamp. (Iron casting without rating, shaped like a C with a threaded bolt and a lock screw.) In case someone in the future happens on this thread, there are some problems associated with generic C clamps.
One, is the lack of rating.
Two, is using such a clamp on a soft metal truss where the bolt can actually deform the metal and cause the clamp to loosen.
Most of these clamps have found their way into the dust-bin of history, but there are still a few around.

There are still a ton of them around, most conventional fixtures still come with a generic c clamp if they come with a clamp at all. And most theaters still use them, there isn't much reason not to. I can't remember the last time I saw someone using them to hang fixtures on a piece of truss though.