I recall doing this for one of the other lists a few years back. The short
answer is don't worry about it. Use grade 8 bolts, and don't bounce up and
down a lot removing fasteners.
The long answer is simple math. Let's say that you have 4 5/16" bolts to
hold the motor to the stand. The motor weighs in at about 425 pounds. Now,
I should walk over to the shelf and look this up in one of my Carroll Smith
books or a strenth of materials text, but I am somewhat lazy. Let's say that
the bolts your friend is using have a 25,000 psi (at the thread) rating.
This would be a good hardware store SAE grade 8 bolt. I could be wrong by
a factor of two on this, but bear with me.
So, 25,000 psi means that one square inch will support 25,000 pounds. A 5/16
bolt has an area of 0.07 square inches, using the good old "pies are square"
formula. So 0.07 times 25,000 is 1,750 pounds, per bolt. So 4 of our 5/16"
bolts can support 7,000 pounds. But since I may be off by a factor of two,
let's say 3,500 pounds or only about 8 TR6 motors.
So like I said, don't worry. Now, if your friend wants to get some AN bolts
at 125,000 psi ...
mjb.
|