welding to truck frame?

The question of whether you can weld to it or not is more to do with age of the truck. The newer the truck the less advisable it is.

It also depends where you are welding it.

If it can be bolted then bolt. Maybe you could weld up some saddles that wrap around the frame and clamp to it. That way, no holes and no welds.

But if the frame were just HR/CR mild steel (no tempered alloys), it shouldn't really matter, should it?

Point is, a '90s GM truck frame is very unlikely to be mild steel. Ernie has spoken, anyway. That settles it for me! - GWE

Right you are, Ernie is the master! Besides, if it were my truck I wouldn't let you weld on it "just in case"; better safe than sorry. Lane

Greetings Grant, I know that newer vehicles use heat treated frames. This allows lighter frames to be used. I don't know what year this became universal for American auto makers but it has been several years. The reason that welding is a bad thing is because the heat affected zone will get weaker. If I recall correctly the actual alloying elements were present in minute quantities and the heat treat was not done the way normal steel is. The thing that makes this steel so attractive is the low amount of alloying elements and the lighter gauge. Apparently these two money saving features more than offset the cost of heat treat. I betcha Ed knows. ERS

"Grant Erwin" wrote: (clip) He wants two (or maybe four) pieces of heavy flat bar to be attached to the truck frame rails so that they stick up on either side and guide the bed rails down dead onto the truck frame rails. (clip) ^^^^^^^^^^^^^^^ Would it be possible to weld the guide bars to the rails of the dump bed, instead? They would wind up in exactly the same position, but attached at the top instead of the bottom.

This is a good idea, I'll check it out. - GWE

You still have to be very careful HOW you weld to it or you can distort the frame.

From what I reacall from my materials classes, most modern frames (and unibody designs) are made from so called HSLA (High Strength Low Alloy) steel. The great strength they have is from a very tightly controled alloy mix. If you get the alloy ratios even slightly wrong, you loose most of the strength. The problem with welding is that you are melting the metals and adding some other filler metal. There is no telling what the alloy will be at this point, but I can almost gaurantee it won't be right. As a result, you have a weak weld and as far as the frame is concerned, any place you welded, you might as well have cut. Of course, it is possible to weld the stuff, if you know the alloy compositions you are working with and use the proper techniques and fillers... that is how the factory does it. Then you get into heat treating and the like. Keep in mind that the frame was probably cold worked (which makes the material tougher) and possibly tempered (to keep it from cracking). A weld is a casting, so you are not ging to have any kind of desireable (or really controlable) microstructure compared with the rest of the frame. Again, with the proper techniques, materials, and information, it is doable, but odds are you won't be able to get that info or equipment. I think you are better off bolting rather than welding.

-- Joe

-- Joseph M. Krzeszewski Mechanical Engineering and stuff snipped-for-privacy@wpi.edu Jack of All Trades, Master of None... Yet

Not a good idea at all, as any malalignment as the body comes down causes wear to the truck chassis. Standard practice is to bolt such guides to the vertical side of the truck chassis.

Tom

Don't forget to provide a lead-in taper on the guides so that you don't have to exactly mate them when the dump is closing. I'd also put a U section over the frame of the truck so that the frame doesn't get rubbed by the dump doesn't directly rub on the truck frame.

-- Why isn't there an Ozone Hole at the NORTH Pole?