Don:I am curious if you have looked at any of the aftermarket frames made by The Roadster Shop, Art Morrison, Detroit Speed, Speedtech etc. It seems they all break the rules you mention but I don’t recall hearing of a single failure of any of these frames/chassis. Perhaps it is because typical performance cars don’t usually see anything approaching 100 thousand miles over their useful life? Curious to hear your thoughts.
Edit: Here’s an example of the sort of frame I mentioned. Made up from welded flat plate. It’s very common.
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I’ll also add that the factory frames I have experience seeing have some atrocious looking welds, but then I am not a welding engineer.
Thanks,
Don
I don't know how I made that photo go from my iPhone to the old Apple computer!
The thicker steel will need some solid form material, steel is the best but some thick aluminum could work.
I have hammer formed many parts. Depending on the material I have made the forms with steel, aluminum, hard wood and even polycarbonate.
View attachment 26704Here is a crude sketch of the cross section describing the hammer form Chis explained:
I would go about it in a simple way.
Perhaps plug weld in some fish plates inside.
The "KISS" method.
The only thing I might recommend for someone choosing to go this route is to extend the leg down on your top formed piece so it welds into the trimmed down frame about in the middle of that frame's depth. That's one of the "neutral axis's" of the frames cross section. It is here that the loading stresses change from compression on the top to tension below. Essentially--no stress from weight loading. Shear and torsion--another matter but not the bad actor. The Art Morrison frames Don H. mentioned earlier in this thread all have the electric resistance weld (ERW) seam of the tubing oriented here--for good reason. It is also harder to tube bend with that weld seam on either the tension or compression side of the bend and end up with pieces being the same length after bending consistently. The ERW seam weld is about 8-14% stronger and stretches less in power assisted bending on a typical Pine bender or the like.View attachment 26704Here is a crude sketch of the cross section describing the hammer form Chis explained:
This is something easily overlooked. It is also used in wide wood boards, such as floor joists. a small hole in the middle doesn't reduce its strength.The only thing I might recommend for someone choosing to go this route is to extend the leg down on your top formed piece so it welds into the trimmed down frame about in the middle of that frame's depth. That's one of the "neutral axis's" of the frames cross section. It is here that the loading stresses change from compression on the top to tension below. Essentially--no stress from weight loading. Shear and torsion--another matter but not the bad actor. The Art Morrison frames Don H. mentioned earlier in this thread all have the electric resistance weld (ERW) seam of the tubing oriented here--for good reason. It is also harder to tube bend with that weld seam on either the tension or compression side of the bend and end up with pieces being the same length after bending consistently. The ERW seam weld is about 8-14% stronger and stretches less in power assisted bending on a typical Pine bender or the like.
I spent a few years at Fords Dearborn Engine plant in my youth, and saw a lot of quality control issues wayyyy back then.I can't speak for older vehicle weld checks
I also saw them ship parts with bad Delta welds even though they were supposed to be 100% good.