The Stovebolt Site Forums The Parking Lot Big Bolts Boxing frames, tempered frames, etc.

I was planning on boxing a couple of sections of the frame of my 1959 Viking "Shorty" school bus, plus filling some non-factory and factory holes. I've heard that some frames are "tempered" and heat will weaken them. I don't think this is the case with mine, but I'd like to know before I move forward. Anyone?

My 48 Chevy frame had stenciled on the inside I presume from the factory something to the effect of "do not heat or weld on frame"
This same message is also found on many if not all large truck frames today.

I would avoid welding on your frame.
I would also not want to box it not only because it involves welding, but because it changes how the frame acts. It was designed to flex, boxing it in places can lead to a cracked frame at the transition from boxed to open.

Grigg

I agree that you will only weaken your frame by welding on it and boxing it will take away the ability to flex and it will find somewhere to crack. If you have a real urge to strengthen a frame, a glove bolted to the outside of the frame would be the way to go. Heavy haul frames are double and triple. Why are you trying to strengthen the frame in the first place?

The frames of today and for a long time often have stickers on them about welding. That is placed there because of the hi-tensile material used in the frames which may exceed 110,000 psi. Generally above that they are reinforced by adding L sections or by doubling or tripling the rail. Sometimes frame are increased to 3/8" material as in the case of aluminum rails. Just depends on what RBM the Engineers are going for. However there are no "tempered" frame rails in my experience. Your 59' schoolhack is pretty likely to have a std 50,000 psi frame. As for the holes, put bolts in them. I have to echo crenwelge on the "why" part.

Frame rails can be welded but it takes real knowledge and is generally discouraged which is why you see the stickers/stencils. There is also the liability issue which can be very real in todays litigious society. Messing with a frame is like having your spine operated on and having your neighbor do it IMO.

Frames CAN be welded, but it takes an experienced welder to do it... Some rules to go by:

1: Always weld the LENGTH of the frame... Never lay a VERTICAL weld..... It WILL crack right beside the weld... Welds create heat stress lines..... Those lines need to be at a right angle to the frame stresses.... Think about it, your frame sees very little stress trying to "stretch" it... But much strain trying to "bend/break" it.

2: Always weld in small random stitches about 1" long.... Let cool until room temperature before laying next set. Lay them evenly back and forth to avoid warpage.

I've welded many truck frames over the years and we did many every month in my business. Most were heavy class 8 trucks. All were welded vertically from bottom to top with a DC welder. Never had a job come back in over ten years but we did do a lot of amateur DIY jobs over. Proper reinforcement, knowledge, and using approved engineered techniques is the secret to a good frame job.