The school where I'm taking welding classes has an old flatbed truck with recesses for "stake" sides. The recesses (22) are 1 5/8" by 2 7/8", which don't fit any available lumber or steel. The instructor wants to make low, easily removable stake sides so the truck can be used to haul sheets of steel and other material without having to tie it down. He's leaning toward using metal rather than wood.
The recesses aren't very deep (maybe 3"), and there's no place to put a pin or anything else to hold them in place.
What would be the best way to make the sides, and how should they be secured to the bed so they won't come off when the truck hits a bump?
Lightning should strike the truck designers who over the last century provided stake pockets that fit no standard sized expedient - a standard 2 x 4 for example or a dual use 2 x 4 and 1 1/2" IPS SCH 40 pipe.
I suggest if the pockets are designed so the stakes go through to provide them with tangs that accept a through bolt. If the pockets are blind, jig drill them to accept a 1/2" bolt or ball pin from the outside that engages a captive nut or a hole in the stake. I suggest using a 1 1/2" x 3" rectangular x 0.120 wall tube steel stake whose ends are deformed on a press to suit the stake pocket.
Better tie the load down anyway. At 60 MPH, even a 4 ft x 12 ft 1/4" steel plate will fly up off the truck bed and soar away under the right conditions. That's almost 500 lb gone airborne in traffic on your liability insurance.
And a double hex on them for putting three angles on them. I had a customer who installed outboard pockets on his bed rails -- really nice job. I got to torch them off for him because the pockets they used would only work inboard. The gates leaned out about 15 degrees in their new pockets. On top of that, forklifts running into the 1/2"x 4" rub rail they added would have bent those flimsy things to crap right quick.
It's not worth the trouble to make stakes. Call a truck shop and find your local dist. Make sure it's a dist, as the markup on stakes, hardware and apitong is huge. I would also recommend against the aluminum panels they sell. Go with wood. The aluminum are light and require no maintenance and don't hold up to the abuse that the gates receive. The recesses in them also don't line up with the screw holes in the stakes.
As to them falling out -- I just don't see it happening. They should all be latched together and to the headache rack. There is a bunch of friction to overcome to get one to fall out. Millions of trucks run around everyday without anything but gravity holding them in.
If you need to turn this into a welding project, climb underneath and see what a crappy job the factory did installing those pockets. It'll stretch your skills rewelding them in place. Ear plugs and a leather jacket recommended. While you're at it, throw some strap winches on there and weld up a tommy bar to tighten them.
If you guys do decide to weld some type of panels on, shim the stakes in the pockets so they'll fit after the welding twists them.
I have an old Army truck with a stake bed - the wood is an odd size and made from oak but the vertical pieces are a light (16ga) sheet metal box tube that goes into the pocket and has flanges to hold the slats. The vertical stakes have thru-bolts holding them to the bed and carriage bolts holding the wood to the slats.