Chassis Shortening. Need Advice.

I am certain that this has to have been covered but I couldn't find it for the life of me so I apologize if I missed something.

I am going to be shortening my frame by about 2.5 ft. My plan as of now...

Sawzall the frame w/ straight cuts(because I am going to be cutting just to the outside of two cross members.

Separate the rails and have channel bent to fit inside of the stock rails 1.5 ft on each side of the cut.

Weld in the channel and piece together the two halves.

Box the rails.

Build front and rear cross members and re-connect the rails.

Any help would be much appreciated. Thank you.

 

Some pic's would help. What chassis are we talking about? Do you have it in a jig or on the floor?
Scotty

 

How well can you weld? with proper weld technique all you need to do is reweld and box.

 

you can also weld a 3/16 plate 5 or 6 iches long over the joints in the inside of the rails before you box them to add strenght........

 

Sorry for the vague description. I haven't done a lot of welding but I can run a decent bead and I have some pals that are certified. The frame is a 1918 Studebaker. I'll get photos up asap. As it sits it is on sawhorses. For connecting the two halves I was basically going to use a level to try to make sure they were straight. No jigs... I might try to rig up a jig for building in the cross members to try to make sure the frame is square. I hope that helps. Thanks

 

i would have the buddies weld it. no offense, but not having much time under the hood can be bad when it comes to a frame, or anything for that matter. welds can still "look good" to the un-trained eye. and have hardly any penetration, which is a bad deal. hope i dont offend, just think of the worst case scenario of working on a frame or other drive-train components. its like having the guy at taco bell rotate your tires, or fix your brakes!

 

I agree that 3' of inside channel is overkill. only the joint itself needs to reinforced and that could easily be accomplished with the boxing you propose. Also, as the frame gets shorter it is, in effect, strong as the beam loading is reduced in the center. Nonetheless, I would still box it to ensure strength.

Ray

 

wouldn't the welds be stronger if you cut the frame on a "Z" instead of chopping it flat ??? I know that's how we did it on tractors at the dealership that i worked at ... and maybe fish-plate the welds .. might be overkill ,,, but it works on loader arms ,,, and i would be sure that it won't come apart at better than 100 mph ...

 

Use your best welding buddy, If you can establish some sort of a fixed line on the frame, tack a piece of nice straight angle stock to the frame rails on each side, let them run out 2 feet or so in each direction of the cut, do your math on the cut and tack your shortened section to the tacked angle iron, do some nice tight fitment tacks and some dimension measurements, check your planes on the frame rail, properly weld your butt joint on both sides, go to the inside of the rail and properly weld in an elongated diamond shaped piece of stock to the frame rail over your butt joint, watch your heat and warpage, you'll soften your frame and ruin it, I highly recommend a TIG, Make yourself a boxing plate about 18 inches long, use a decent material, you can put in some punched holes in it and some finish work to it to make it detail nice. Attach the box plate, polish out the butt weld on the exposed side.
You would like to practice this on some junk plate, make your welds and try to master your heat sync and distortion, practice a butt joint, polish it out and look at it close for inclusions and deep pit spots that dug in too deep. perfect the technique on some junk first. Have fun.

 

It sounds like you are just taking a chunk out of otherwise straight sections of a frame? You aren't 'Z'ing or anything else? Just chopping a piece out, right? Then you make your cuts at an angle, like 45deg. This gives you greater surface area to reweld to. You don't want to make your cuts across from each other on the rails either, that just creates a natural weak spot. If they are directly across from each other then make the diagonal cuts opposites.
I don't know about studebakers but a ford frame changes its' heigth quite a bit in a couple feet. This is for good reason, it allows the frame to flex and 'work'.
Remember, it is always more complicated than it looks.

 

Wow. Thanks for all the great advice. I agree with having a buddy weld it... I don't feel like learning how good I am at welding by whether or not my frame falls apart while driving... I can't cut at an angle because there are cross members on either side of the cuts. The Studebaker frame is flat for quite a while. It only changes at the very front and very back. Francisco: thanks for the very detailed step by step. This should be a fun process.

 

If you have enough frame width this method works pretty well for a lot of guys.

This is borrowed from another board and was actually about shortening a pickup frame but the concept is the same. You will have to use your own measurements.



One of my buddies has shortened several frames on rigs from half ton pickups to 2-1/2 ton trucks with this method.

I can't see cutting any frame and not matching it side to side, that doesn't really make good sense and I don't think it would add any strength to the job.

If you aren't sure of your welding skill, I'd suggest doing the cutting and fitting and aligning and then tack it together and make sure it is right and then have your welder buddy do the finish welding. I used to do that when I was building my T bucket.

I'd for sure box the frame and might cut down and use a short section of the original frame inside the splice to add a bit of strength rather than using angle iron.

 

That is the best way to shorten the frame, it will keep it nice and strong.

 

Ok... So I think I will try the method above. I might have to take a couple rivets out first but it seems like it will be the strongest and ultimately that is what I want to end up with. Thanks so much for all of the advice and help.

 

Just a thought but have you considered using new 4x2 RHS. 90 year olds steel is still 90 year old steel.

Fish plates are a great idea too. You only need them on one side and making them as long as twice the depth of the rail is what is prescribed here. ie using 4x2 RHS the fish plate would be 8" long. Curve the ends as well.

If you do go the RHS route there is some info on making a frame in the link in my signature. Its actually quite easy.

Either way make one rail and replicate it exactly for the other side.

 

RHS? I could just build new rails. How could I replicate the curves? Seems somewhat involved and complicated. The above photos show where I am planning on cutting and the cut lines.