Seemingly not addressed here is just how much load might be placed on
these motor mounts and the three bolts holding it to the frame. It has
been forever since I removed mine (pre 1974) so I don't remember if
these three bolts are 5/16 or 3/8. If they are 5/16 the cross sectional
area is 0.0767 sq inches. Published yeild on Grade 5 bolts is 120,000
psi and shear is taken to be 60% of that number. So shear for one bolt
would be int he neighborhood of 72000 psi. That works out to be about
5500 pounds per bolt to shear it off. The notor weighs about 450 pounds
per so and that is divided by two. So even with a 10 g load the max
loads would be around 2250 pounds per side. And there are three bolts if
I remember correctly. Plus this is a clamped joint with friction so that
makes it even more conservative.
So yeah, Owain, run a tap through the threads on the motor mount plate
to make sure you don't bung up any more threads or a bolt and put in a
bolt that will go at least flush with the through side surface.
Naturally if the bolts are 3/8 inch it is even better. So put a bolt in
it and don't worry about it.
Owain Lloyd wrote:
>the 1/4" longer bolt will not poke through by more than a fraction.
>the existing threads appear sufficient to hold it with this extra 1/4"
>On Sun, Apr 6, 2008 at 8:43 PM, <CoolVT@aol.com> wrote:
>>I would think that if there is room and you can get at it that you could use
>>a longer bolt and where it pokes through put on a lockwasher and nut. It
>>that will work it should be at least as strong as it was originally.
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