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Thread: Looking for the right kind of clamp to put fixtures under an I-beam

  1. #1
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    Looking for the right kind of clamp to put fixtures under an I-beam

    I need to temporarily install some small overhead lights in a venue that isn't made for shows... and by "venue" I mean "my patio."

    The patio cover has a nice aluminum crossbeam. It isn't actually an I-beam though, it's more of back-to-back C shapes. I have seen a single "C" referred to as "channel beam," but I don't know what you call this.



    Surely there must be some kind of clamp that will latch on to the bottom of this beam, and provide a means to affix a light bracket... but I cannot find it.

    As second choice I am open to the idea of running speedrail under the beam so I could use MFL clamps. I'd need some kind of bracket to go around the posts OR beam and support the speedrail... Again I bet that part is out there somewhere, but I can't find it.

    I'd appreciate any leads!

  2. #2
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    That beam looks like a box in that pic so I don't see how a clamp would work, and if it's aluminum you may be better off permanently attaching a 1.5" or 2" pipe section to hang the fixtures from with a standard O-clamp.

    I have used beam clamps to hang fixtures, they have a threaded hole that will accept threaded rod or a bolt. These are designed to pinch the lip of a steel beam which won't distort like aluminum. Check these guys for a range of clamp styles McMaster-Carr


    Last edited by conanski; 09-28-2021 at 08:14 AM.
    Paul O'Brien
    Old Tech Guy
    www.Techott.com

  3. #3
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    Quote Originally Posted by conanski View Post
    That beam looks like a box in that pic so I don't see how a clamp would work...
    I guess you'd need a clamp that could pinch the bottom without putting pressure on the lip.



    Or, like you showed, something that pinched each side of the beam, with a crossbar underneath. The clamp you posted is definitely in the right ballpark. I'll look at more beam clamps. Man, there must be something that will work... I just need to hold up a couple of PARs and small moving head spots and I'd really like to do it without drilling!

  4. #4
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    OK, "universal beam clamp" was a useful search term, thanks. This stuff seems to be the right shape. Need measure the flange and see if I can get one of the right size to test.

    https://www.erico.com/category.asp?category=R387
    https://www.fastenal.com/products/details/44620

  5. #5
    I wouldn't use a standard beam clamp on that, I'd be worried about damaging the aluminum.

    I'd use two short sections of unistrut, one above the aluminum and the other below.. with two lengths of threaded rod to clamp them together. Then attach the lights to the unistrut. And some tape on the unistrut where it contacts the aluminum so it doesn't scratch it.

  6. #6
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    This is the right answer above.

    If it is a permanent install you could look into powder coating the strut channel and hardware to match your beams.

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    I see what you mean. That would definitely work.

    I did find a couple of clamps that might work -- applying pressure only to the flat bottom of the beam, and not applying any pressure or shear to the flange. If they fit as I hope they should clamp adequately in a way that is safe for the aluminum. If that doesn't work, then I'll look at enclosing the beam as suggested. In that case I might even use wood blocks instead of strut, as it is temporary.

    Time to order some safety cables too, haha.

  8. #8
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    OK, I think I have a winner. This is a Minerallac 602B. All the clamping force is applied to the flat portion. It holds tightly without marring, and the delicate flange isn't even touched. I think this will meet my needs.

    The real test will be to see if a moving spot wiggling around loosens it, I guess.


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