Lifestyle: toy repair w/ J-B Weld

The tutor wonders about a pending toy repair.

My younger son has a toy he really loves that broke. Specifically, a pot metal part sheared off. It’s a toy out of production, so can’t be replaced.

Looking at the breakage, a repair seemed unlikely to work. I went to the hardware store and explained the situation. The man handed me J-B Weld: “If anything could work, this will.”

The J-B Weld label suggests a tensile strength of 3960 psi. The tensile strength of pot metal might be around 40 000 psi. In the toy, the strain on the metal part is not tensile, but rather shear. The shear strength of pot metal is around 75% of its tensile; if the same for the repair, it might be around 3000 psi.

I estimate the surface of the repair to be about 1/64, or 0.015625, inch2, suggesting a repair strength of 3000(0.015625) = 47 pounds.

The pot metal part stretches an elastic. Stretching the same elastic even further by a hanging mass, I’ve determined that the toy’s pulling force is less than 2.5 lbs. With estimated strength of 47 pounds, the repair should hold.

J-B Weld needs 24 hours to cure; the repair has had about 36. I guess we’ll know soon if it works. I’ll keep you posted:)

Source:

wikipedia

sciencedaily.com

jbweld.com

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.

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