ididieseler
Registered User
i'm looking to cut out about six inches a little ways behind the cab, how should I reinforce it when I splice the frame back together?
What he said.You can simply cut a straight line, weld it, then fish plate. The important part is to make sure every thing is clean and true before you put it back together. Stick, wire feed, flux core, tig, what ever you prefer to weld it with as long as you or the person welding is competent. The frame you are altering is not some special alloy that involves any particular process. It is only a higher tensile strength than mild steel (around 70,000psi). I do recomend the fish plate be cut as a diamond shape more than rectangular, or miter the corners generously on the rectangle. I have a vast amount of experience in modifying frames from 1/4 ton to class 8 trucks. Not all are going to require the same technic.
I have a welding tips book I bought long ago, and something that is preached in the book but has not been mentioned in this thread yet; They say if you are going to plate the frame, do not weld the plate all the way around and close it in with welds. Only weld parallel to the longer sides of the piece you are welding. In other words on a truck frame, if you are going to weld a plate on the side to help re-enforce your splice, only weld it on along the top and the bottom, do not make vertical welds and close it completely in.
They say as you weld the piece heats up and expands, and when it cools off, it shrinks back and creates stress. It's easier for the frame to expand and contract on along the top and bottom edges as you are welding, and then shrink back. If you close the sides in, it's very difficult for the frame to swell up and then contract when it cools, and it's also almost impossible for the plate to swell up and then contract back when it's already welded on the top and bottom. All looks good when you are done, but you don't realize all the stress the area is in just sitting there, and then when it's put in service it usually eventually cracks somewhere along one of the welds.