best way to mount body to frame

[Richrad]

I'm ready to mount the (mostly completed) body of my trailer. My body has a plywood floor and the frame is 2X2" 1/8" wall steel tube. Best to use u-bolts, weld on brackets, or drill right thru frame? Or something else that hasn't occurred to me

[working on it]

• I bolted/screwed my plywood floor to the metal frame, in two stages. I used PL Premium adhesive to seal between frame and floor, then sealed any open spaces from underneath, with spray-on (rattle-can) undercoating (goes on dry, absorbed by the wood). http://www.tnttt.com/viewtopic.php?f=35&t=68349&hilit=+tek#p1202710

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  carriage bolts and tek screws.jpg (131.65 KiB) Viewed 1825 times

[Pmullen503]

I'd avoid drilling holes through box tubing.

Long carriage bolts on either side of the frame member with a strap connecting them would also be an option.

[Aguyfromohio]

Use self-drilling, self-tapping deck screws about 1 inch long. The technical name for the head is "wafer head".
The heads pull down flush to the plywood nicely.

[Tigris99]

I'd avoid drilling holes through box tubing.

Long carriage bolts on either side of the frame member with a strap connecting them would also be an option.

actually drilling through is not a bad idea because chances of welds being perfectly sealed are rather slim on a production trailer. That's why most things made out of tubing like this have drain holes.

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[Andrew Herrick]

Unless you're dealing with a particularly top-heavy or portly camper, I'd highly recommend choosing self-drilling TEKS trailer decking screws or self-tapping trailer decking screws (no wings). Attach the subfloor firmly to the trailer by fastening the subfloor every 6-8 inches along the perimeter and interior cross members, and then securely attach the walls to the subfloor. The most important connections are the subfloor to the main rails and the two end cross members.

My second recommendation would be to weld 2x2 angle onto the cross members, like you suggested. You can either use carriage/elevator bolts with a hex nut, or you can use weld nuts with a hex/socket bolt and opt. counterbored hole. There are other fastener combinations, but those two are the most practical.

Remember: A run-of-the-mill 1/4-inch dia. self-drilling screw can carry almost 1,000 lbs in static shear. I once had a wheel almost pop off my 6,000-lb truck; it rolled for a good 1/8th mile on a single stud. So don't overthink it