Do aluminum c-clamps require safety cables?


A few months ago, an installer told me that The Light Source Mega Clamps had some kind of rating and hence didn't require a safety cable. Now of course, personally I safety cable every piece of equipment I hang. However I wanted to know if this advice was a bunch of malarkey or if there was something to it. I know that cast iron fails catastrophically at its yield strength while aluminum deforms before failure. Aluminum is also more elastic which I presume makes it better suited for clamping to things. I think aluminum is also "stickier" when it comes to bolts coming loose over time due to vibration and temperature changes.

It was fun looking up stress/strain curves for cast iron and aluminum. Any thoughts?

And for any newbies out there who wader across this thread, just play it safe and use a safety cable. You don't wanna be responsible for someone's death.
Safety cables are a good practice regardless. Yes, cast iron clamps can fail unexpectedly like soft butter, but in a calendar year, I'd bet the number of incidents where a fixture falls or almost falls are much higher when someone doesn't tighten something down than when a cast iron clamp fails.
I've always been of the opinion that you always do it because you don't know what kind of dynamic loads that fixture could take if it strikes something while moving. I've also been of the opinon that a failed C clamp falling would do the same damage as a falling fixture.
Aluminum is actually not that elastic compared to steel or iron. Most cast c-clamps are rated for “one fixture” and that’s due to the nature of the casting process. The aluminum ones are not only much stronger mechanically, but tested and marked with the load rating.

As far as to safety or not, if I was short safeties for fixtures hung with rated clamps I wouldn’t loose sleep over it.

What I find really interesting is the use of a safety with an unrated dog clip on a 100lbs moving light with two rated clamps, and the safety running in a giant loose loop so that if the unit were to fall your are generating a giant dynamic load on the unrated safety.


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