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Re: [Tigers] please vote on my thread repair decision

To: owain.lloyd@gmail.com
Subject: Re: [Tigers] please vote on my thread repair decision
From: drmayf <drmayf@mayfco.com>
Date: Sun, 06 Apr 2008 15:51:59 -0700
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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