Analysis of Pulley/Sheave Pins Question

[IngenieroSuarez]

Can the pins in pulleys/sheaves be modeled as fixed-fixed?...if so, what standards must be followed for hole sizing? Is their a standard to follow?

I have always modeled them as pinned-pinned(symply supported), but I was asked this question and not sure about it.

I also found this info on the engineersedge website, but not sure if it would apply:

http://www.engineersedge.com/general_tolerances.htm

 

[Co]

Why are you modeling the pins as simply supported or even fixed-fixed? Are you performing some kind of deflection analysis? Otherwise I would suspect that the pins you need for a pulley/sheave should be designed based on the shearing separation planes and von Mises stresses.

cheers,

 

[IngenieroSuarez]

Coppola,
I am also doing shear stress calcs, I just thought I needed to include bending calcs as well.

So based on what your saying the worst case for pins is shear stress.....Right?

 

[Co]

Well, I don't know your exact case. However, in the vast majority of cases what you said is right and it would be customary to design the pin based on shear stress. What kind of system is it?

cheers,

 

[IngenieroSuarez]

Actually this is more of a pin clevis design, the reason I mentioned sheaves was that I assummed similiar analysis. The current design is a two clevis design (one inside of the other).

I have referenced "Schaum's Machine Design" for clevis design and he includes bending caculation for a clevis pin.
Here is the link to his book:

http://books.google.com/books?id=ee...haum's+Machine+Design+clevis+design#PPA140,M1

 

[Co]

Understandable. Have you determined what mode of stress defines your system design?

 

[IngenieroSuarez]

I found this thread:

http://www.eng-tips.com/viewthread.cfm?qid=81231

This should of been the question I asked in the first place.

I am still debating what mode of stress defines my system.
I am leaning towards doing simply supported and design for shear stress and make sure that the bending stress does not go over yield strength.