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Joined: Dec 2013
Posts: 28,392 Likes: 569
a.k.a. Dingle Johnson
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a.k.a. Dingle Johnson
Joined: Dec 2013
Posts: 28,392 Likes: 569 |
Hanging harbor freight electric hoist in the garage ceiling to lift the convertible hardtop using a unistrut trolley. The ceiling joists are 2x14 i-joists so I'm going to have to hang blocking between them to support.
The whole rig (hoist with hardtop) will be about 100 pounds. I'm pretty sure 2x lumber will support the weight with 2 attachment points, but does 2x give enough meat to drive lag bolts into? Should I consider 4x to make sure there's enough material for a lag bolt to grab into? I have also seen a guy use 4x4 and drill all the way through it to bolt through with a washer or plate on top, which may be overkill for my load. Tension capacity of lag bolts is as follows: 1/4 inch lag bolt - up to 100 pounds per inch of thread. 5/16 inch lag bolt - up to 200 pounds per inch of thread. 3/8 inch lag bolt - up to 272 pounds per inch of thread. However I would double check the weight of everything: Hardtop, Rigging, winch, attachment material, everything and then design the bolted connections for at least 150% of what you calculate. Personally I would have at least 4 attachment points to the joists and make a "H" shaped mount out of 2x4's with all 4 ends of the "H" lag bolted to the joists. Can you simply bolt through the flanges of the joists? How much Flange width do the joists have? Anecdotal engineering... I've personally seen porch swings mounted to ceiling joists with 1/4" lag screw eye bolts and those things routinely hold 2 adults, plus the dynamic loading of the swing going back and forth. Two mother in laws on that thing and you'd be going over 600 pounds. 
Last edited by Irishguy; 03/16/24 06:29 PM.
"When I say ever thing I mean ever thing." - Frankie
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