Figured someone here might find this interesting. Here’s a galvanized steel flatbed I built for my truck the summer before last.
The truck used to have an F350 dually box on it, but I had a recap drive tire come apart and destroy the box floor, box side, plastic dually hip, rear bumper, tailgate, mudflap bracket, etc. I got a decent check from the insurance company and used it to purchase a complete rear frame cut from an International 4300 with air suspension, a used wheel lift from a rollback, and the materials required to build this flatbed.
Lots of head scratching went into this build to eliminate the possibility of warpage. You can see how the tiedown rails, front bulkhead, wheel tubs, and toolboxes are separate elements that bolted into the skirts after all the parts had been hot-dip galvanized. I knew if I welded everything into an assembly prior to giving it a bath in molten zinc, the stresses would concentrate in certain areas and cause the flat panels to bulge and ripple. Allowing the 12ga skirts to expand and contract unencumbered seems to have allowed them to return to their original dimensions when they cooled.
You can see in a few photos the holes I left in certain parts of the the body to allow air to escape and molten zinc to enter the forms, as well as the holes I punched for the extruded U-nuts that hold the Apitong decking. These were punched with my old Strippit Sonic 15 thin turret punch, prior to forming the crossmembers on a press brake. Again, lots of head scratching went into the design.
I also pulled the engine out of the truck and replaced the flywheel housing with another that would accommodate an OEM Wabco gear-driven air compressor, then built an onboard air system with a couple of Freightliner tanks and an AD-IS dryer.
This F650 was a regular cab 24ft box truck in a previous life; I rescued it from a Copart lot in 2014 and turned it into what it is today, but that’s a story for another day and probably a different subforum.
I’ll throw a few photos of the original build in here: