Frame reinforcing

[holyford86]

So, as I've talked about briefly here and there, I'm going to be replacing the cab on my supercharged truck (cab currently in paint jail) and while the cab is removed I intend to replace all of the body mount brackets, and repair some minor holes in my frame here and there (428k mile rust belt frame)

I also intend to reinforce it through the center, roughly from where the transmission crossmember is back to the rear of the forward leaf spring mounts. I intend to use some frame sections I saved and had blasted from an 88 I had, which is pristine other than being effectively severed by corrosion directly forward of the radius arm mount (truck was used as a shed for about 30 years) It's perfect otherwise.

What I'm hung up on is whether I should either A: cut off the flanges and use the vertical section and secure it with some welding around the edges and all of the bolts for the miscellaneous brackets or B: cut off the bottom flange and drop it over the top, then adjust the holes as necessary (all rivets will be replaced with 1/2 grade 8 bolts) with no welding, or do something else entirely. I would prefer to not box the frame as it would create further complications and snowball the project further than I would like in both time and budget.

I'm open to any and all constructive criticism, haha.

 

[alwaysFlOoReD]

When I worked at RVHaulers they lengthened frames on class 8 trucks regularly. They would fishplate inside the frame with no flange or welding. Grade 8 bolts. The frames were cut on a 45°angle (thinking back it was probably closer to half way between 45 and 90° ), then welded, then the fishplate added. Iirc the fishplate was about 6 times as long as the height of the frame, with half forward and half behind the weld center.

In addition, I believe it's stronger to find bolts that the unthreaded portion of the shank is in contact with both the frame and the fishplate. Use extra washers where you have to in order to get the locknut on and tight (because the unthreaded part should be sticking out slightly).