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Kalun D · 07-21-05, 04:15 AM

""The problem is that the grip limit is very hard to predict.""

agree, and that's way too much camber gain. Also add to that the radial tire phenomenon of gripping up to a point and then suddenly breaking loose, compared the the more gentle transition of a bias tire.

""My question to the engineers is about the bracket design. What do you think. Its made of 5/16" thick plate and a 2 X 2 X 1/4" angle. All mild steel. I think it is stronger than the original simple "U" brackets. They were mild steel also and 1/8" thick.""

Your design looks good and I don't disagree with leaving it bolt on. You could find a skid pad or cone slalom and do some timed tests and try different camber gain settings. Eventually you might want to weld it but it's probably not necessary.

One thing that is maybe not optimum is your thickness. A bracket like this should be about 1/8" (.125") thick. A typical bracket with this amount of load on one of the original cars or a Mark V would be about 1/16" thick. Granted that's with a welded on doubler washer at the hole and flanged edges which are real labor intensive, but you get the idea.

You are getting some bending loads where the bracket bolts to the frame but I still think 1/8" would work. At this point though it looks like it sort of matches some of the rest of the frame and in order to save a meaningful amount of weight you would have to re-do all the too thick brackets, it's probably not worth it.

On another note I believe angle iron is usually weaker than most tubing, plate, bar etc.

What your looking for is 1018 or 1020,

Angle iron is usually 1010 or 1015 which is ok in this thickness for your application but you wouldn't want to use it in 1/8" in this situation.

Page 63 of Carroll Smith's "Engineer to Win" (1010) "is for lawn furniture, trailer frames and tooling only!"

07-21-05, 04:15 AM	#6 (permalink)
Kalun D Kalun_D 5 Tenths Join Date: Dec 2003 Location: Seattle GT40: Scratch build Posts: 589 Rep Power: 11	Re: GTD rear suspention mod ""The problem is that the grip limit is very hard to predict."" agree, and that's way too much camber gain. Also add to that the radial tire phenomenon of gripping up to a point and then suddenly breaking loose, compared the the more gentle transition of a bias tire. ""My question to the engineers is about the bracket design. What do you think. Its made of 5/16" thick plate and a 2 X 2 X 1/4" angle. All mild steel. I think it is stronger than the original simple "U" brackets. They were mild steel also and 1/8" thick."" Your design looks good and I don't disagree with leaving it bolt on. You could find a skid pad or cone slalom and do some timed tests and try different camber gain settings. Eventually you might want to weld it but it's probably not necessary. One thing that is maybe not optimum is your thickness. A bracket like this should be about 1/8" (.125") thick. A typical bracket with this amount of load on one of the original cars or a Mark V would be about 1/16" thick. Granted that's with a welded on doubler washer at the hole and flanged edges which are real labor intensive, but you get the idea. You are getting some bending loads where the bracket bolts to the frame but I still think 1/8" would work. At this point though it looks like it sort of matches some of the rest of the frame and in order to save a meaningful amount of weight you would have to re-do all the too thick brackets, it's probably not worth it. On another note I believe angle iron is usually weaker than most tubing, plate, bar etc. What your looking for is 1018 or 1020, Angle iron is usually 1010 or 1015 which is ok in this thickness for your application but you wouldn't want to use it in 1/8" in this situation. Page 63 of Carroll Smith's "Engineer to Win" (1010) "is for lawn furniture, trailer frames and tooling only!"