Interference fit required for a given torque

[Pipefreeze]

Hi there,

I am replacing a shaft in a large electric motor rotor pack. The old shaft is to be deep hole bored and removed. I want to shrink fit the new shaft into the lamination pack. However I am now concerned that the interference gained will not be enough to ensure that when torque is applied the two components will not separate.

How do I calculate the interference required for a given torque?

Also does the fact the rotor pack is made up of laminations affect how the interference fit will apply its pressure to the internal bore of the pack?

 

[GregLocock]

The torque is simply the contact pressure * surface area*radius.

The tricky bit is working out the contact pressure. There is an FAQ on this.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[dhengr]

Look at thread725-314067 in the welding forum. I don’t know exactly how your motor was assembled, but I would have several questions before I would start any shaft removal and boring out of the old shaft, and original assembly methods would be one of them. Can the laminations actually take whatever interference fit pressures which might be applied, I doubt that that was the way they were originally fixed to the shaft. And, I’d bet they can’t take those compressive stresses.

Why don’t you think about and explain what’s really wrong with the shaft at the moment. If it is in good shape in most respects can it just be built back up with something like a flame spraying method, and then refinished? Maybe you should talk to an outfit which rebuilds large motors for various alternatives.

 

[Cockroach]

This topic has been extensively covered in this forum. Look up past threads.

Also the web has lots of calculators and the necessary literature for you to write your own model. Pressure vessel theory is one approach, but I've seen Lames Equation in addition to University of Tennessee at Martin.

Good luck with it.

Regards,
Cockroach