Repairing cracked frame rails
I am slowly restoring a 1952 International L-112 pickup and need some advice on the proper route to take with a repair item.
The frame rails are cracked on both sides, the driver side has just started to crack and the passenger side is almost completely separated. Both cracks are located several inches forward of the front bed mounting points under the cab. From the looks of the bed and tailgate this truck was overloaded many times, as both are bowed. The bed droops in between each cross-member and the tailgate is pushed out about five inches in the center.
Since I do not plan on completely loading down the truck once it is back on the road I have considered just welding the cracks. I have also thought about getting a steel plate cut to fit the outside frame rail, welding the broken frame rail then drilling holes through the plate and frame and bolting them together, except then the running board mounts wouldn’t fit correctly. If I did the same thing on the inside of the frame rails, I would have trouble remounting the gas tank on the driver side. What are your thoughts on this issue?
You obviously have to repair the cracked chassis if you intend to drive the truck at all. I always like to go beyond just welding the actual cracks when a chassis develops cracks that are as extensive as the ones you describe. That means either putting plates on the outside or sleeving the rails internally.
As a starting point, you will need to get the chassis properly aligned. You state that the passenger side frame rail is cracked almost all the way through and when this happens the sections of the rail on either side of the crack usually move out of alignment with one another. You can normally manipulate the rail sections into the correct position using floor jacks, some sort of a strong pulling device (a winch, come-along, ratcheting trailer tie-down, etc.) and/or a portable hydraulic ram setup. You can buy low-end hydraulic ram kits for under $200 and you can rent better ones for considerably less than that.
If you’re going to internally sleeve or internally plate and then weld the cracked rails then you need to get your sleeve or plates inside the rail. I can’t tell you how to best do this without seeing your cracked chassis so you’ll have to figure out the best way to do this yourself.
If the rails are fully boxed you may have to separate them enough to get your sleeve or internal plates into position before forcing the frame rail back into position.
A benefit of using internal plates or sleeves is that you can achieve a very strong repair and simultaneously cosmetically finish off the outside of the frame to completely hide all evidence of the fix. This would also address your concerns about the running boards or fuel tank not fitting properly if you attached plates to the outside of the cracked rails.
To secure the internal plates or sleeves, drill holes or cut slots in the original rail on either side of the crack. Once the internal pieces are in place and the frame rail is correctly positioned weld through the holes or slots into the new steel and build up the weld to fill the hole or slot.
If you’re not concerned with the appearance and clearance for the gas tank, and running board mounts can be taken care of, it is certainly easier to strengthen the damaged area by plating the outside of the rails. I would manipulate the rails into their correct position, weld the actual cracks shut, and then weld rather than bolt steel plates over the repaired cracks. The reinforcing plates should be at least 1/8-inch thick, with 3/8 or even 1/4-inch being better, and should extend at least several inches beyond both sides of the crack.