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From: Hank Dozier
Date: March 17, 2002
Brian....First of all, I will not fundamentally disagree with using chain if you can get it around the springs and hold it in place. But..... I do disagree that coathanger or welding rod is unsafe if the ends are affixed correctly so as not to allow sliding action. The same would have to be said of chain as well. This aspect is VERY important! For standard coathanger, it is essentially mild (1010) solid steel rod of about 0.090" diameter. The Yield Strength of 1010 is about 75,000 ksi (psi in TENSION). The tensile strength is about 100,000 ksi. If you assume the spring rate of this car at 750 #/inch displacement, with a displacement of about 3 inches, this will result in a force of 750 x 3 = 2250 pounds. If we divide this by the cross-sectional area of the wire [PI*(0.090^2)/2], we get the following. Stress = (Spring Rate x Displacement)/Cross-sectional area, or 2250#/0.0127in2 = 176838.8 psi. Divide that by the 3 wires holding this force, and the force per wire is 58,946 ksi. This is WELL below the yield strength, much less the tensile strength of 1010 steel. That is why we have 3 wires holding it to equalize the stress. So coathanger or welding rod is safe. Chain is safer, so if you have chain, AND can clamp it in place properly (aircraft clamps??), then by all means use chain.