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I know what follows seems like a HW problem, but it's an actual problem I'm trying to solve with some equipment I will be using.

I am concerned that a bolt I am using will be unable to withstand the forces that it will face, and so I am trying to solve the problem out mathematically as I cannot really do an actual test with the equipment.

I need to find the shear stress that is being put on a bolt.

The bolt is 0.5 inches in Diameter, and joins 3 bars. Each bar has a thickness of 0.375 inches. There is a 1.125 inch gab between one of the plates and the other two. The force on the lone bar is 25,000 lbs. The opposite force on each of the paired bars is unknown, but all the forces balance out to zero.

Please see the attached diagram I've illustrated.

http://postimg.org/image/50ouq73sd/

What I've tried:

Since the bar with F3 is not centered, this problem is unlike any previous ones I remember doing in class, or can find examples of online. None the less, I took the approach of assuming that force was inversely linearly proportional to the distance along the bolt. So F2 has most of the load (75%) of it, and F1 has 25% of the load from F3. I don't know if this is correct (If the relationship is a simple linear one), but it seems like it should be.

Then I tried to calculate the shear stress. Here I confused myself as I found I perhaps did not need to do the previous step at all - even though it struck me as necessary to know each force acting on the bolt. Following the equation for Shear Force of tau = F/A, I ended up just using the force F3 (25k lbs) and an area of 0.3927 in^2 (The x-sectional area of the bolt, times two, since there are two plates attached).

This gave me an answer of 15,900 lbs/in^2... I have no clue if I did it right, or if that answer is reasonable for me.

Any obvious fault in my work? Anyone know what I am missing here, and how to find the shear stress of this bolt? Did I *gasp* do it right?