Shaft Coupling

[Zac H]

Hi

I am trying to design a coupling to connect an extension shaft to an existing shaft. The extension shaft will have a hollowed end section to sleeve over the existing shaft, and the two will be secured with one or more pins or bolts perpendicular to the shafts. I am having trouble sizing the connecting pins. The shafts will be in tension and torsion.

Can anyone direct me on the method to size the pins for these loads?

Thanks

 

[desertfox]

Hi can you provide a sketch of the shafts you are trying to connect and the tension and torsional loads involved.
You might be better trying to buy a shaft coupling off the shelf instead of designing from scratch.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[CouplingGuru]

in order to size the pins you need to use a combined stress formula. however being that you are using the bolts perpendicular to the shaft the stress in tension (axial) torsion (torque direction) will both resolve back to shear on the bolts. This shear will only apply once the friction carrying capability of the bolt is exceeded. First resolve these two different shear vectors into one (axial shear ^2) + (torque shear ^2) = (combined shear ^2) Solve for combined. Once you have combined shear you have to determine the friction carrying capability of your bolt. T=FDu T= torque, F= clamping force, D= major bolt/pin diameter, u=coefficient of friction typically 0.2 for non-lubricated joints.
Solve for F, once you have the clamping force take that off the shear stress. or better yet design the joint to hold all the shear stress and using the clamping force as your safety factor. Just depends how far you want to take it. With all that being said, you are better off buying an off the shelf coupling . . . depending on your horse power and speed it may only be $50.

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