Are offset shear pins able to bear more load?

[Jake2465]

I was wondering about this and did an internet search. But as usual, my searches are so specific that I did not really find anything on it. Let's say I have this shaft that is 0.750 radius and has a tube it applies torque to by means of a cross pinned bolt. Would the setup be able to transmit more torque with the bolt in a perpendicular position, or would it be able to apply more torque if offset before it shears?

 

[T Bredehoft]

The half-essed engineer in me says it would average out, neither would be stronger. what you'd gain in thickness you'd loose in torque.

 

[Latinrascalrg1]

I cant say for sure but i would think the offset pin would allow more torque before shear failure. When offset from center the rotational force would need to shear through slightly more of the pin material because its at a point where the cut would go diagonally through vs being on center where the rotational shear force only needs to go through the thickness of the pin at a 90°cut. So Thats my theory and only my theory as i never actually thought about this until your post.

 

[higgite]

Hi Jake,

I don’t know the answer to your question, but even if the offset will allow more torque to be applied before shearing the pin, why would you do that instead of using an appropriate shear pin on centerline?

Tom

 

[Jake2465]

That was my thought as well. My thought is that the diagonal load would basically equate to a change in vector direction. Some load is trying to shear the bolt and some of it is now trying to push the tube out of the way so the inner shaft can round itself out.

 

[Jake2465]

Hi Jake,

I don’t know the answer to your question, but even if the offset will allow more torque to be applied before shearing the pin, why would you do that instead of using an appropriate shear pin on centerline?

Tom

Curiosity mainly . I always ask these kinds of questions to gain insight into practical applications. One example that comes to mind for me is around tube welded frame and a square tube welded frame. There are tradeoffs to both and the project parameters determine which one would be better. I found that the weight savings I would get from the increased efficiency of the round tube was not worth the extra work in the proper fitment of those tubes to make sure the weld seams were ideal.

So, everyone had told me to use round tube because it was superior to the square tube. But, I found that with my limited skill and equipment, the square tube was ideal for me and taking a slight weight penalty was worth getting the frame welded together.

 

[silence dogood]

I'd stick to the known shear pin ratings. A shear pin is like a fuse. Too big of a fuse, you burn the house down. Too strong a shear pin, you break something major on your lathe.

 

[silence dogood]

I'd stick to the known shear pin ratings. A shear pin is like a fuse. Too big of a fuse, you burn the house down. Too strong a shear pin, you break something major on your lathe.

 

[silence dogood]

Sorry about the last two repeats. Have no idea how that happened.

 

[Bi11Hudson]

Most of my mechanical experience has been on large bridge cranes, where everything on a shaft is keyed instead of pinned. BIG cranes, 25 to 300 tons, not a "budget" hoist. I see what your question is, and concur with most responses, stay with the center factor rather than the offset.

For my thinking, a pin would be more useful in a high speed application. There would be far less imbalance at center. The offset that you show would be badly imbalanced at speed. Although I have seen those before, on electrical gizmos of negligible speed, where an imbalance wouldn't be a factor. And like most responses, no "book larnin' ", just common sense and experience with old equipment.