Bearing problem

[cancsco]

Hi,
I have a crankshaft which rotates with a 6000 rpm speed.
This crankshaft is driven by a motor and I have a setup where in the crankshaft is loaded both sides( motor in the center)
I have installed 2 bearings on each side to support the shaft. The ball bearings that I use are 12X24X6 on both sides.
Now the problem is with the bushing. I am using an aluminum bushing clamped to the motor assembly and the bearing is glued on its inner race to the shaft.
The problem is whatever I try to do, the bearing gets its outer race spun and gets damaged soon.
The temperature conditions is around 70 degrees Celcius.
I suspect it is because of the difference in thermal expansion of steel bearing and aluminum bushing.
My question is what is the regular practice in choosing the bearing and bushing materials.
Should I be using the same materials or of different kind.
Any help or suggestions is greatly appreciated.

 

[diamondjim]

How much heat is being generated?
Is the outer race pressed fit into
its housing? You might want to post
this to the bearing design forum.

 

[Cockroach]

"...bearing gets it's outer race spun..."

I suspect that the bearing and housing are not proper fits. Excessive wear on the outer ring would be exactly what I would expect. Download the NTN bearing program off the website and review your fits.

With respect to material differences, it depends on the particular application. In your case AND should there be temperature differences I would expect thermal effects to aggrevate your problem. Remember that housing/bearing thermal expansion can also increase fit tolerances since the expansion coefficients are material dependent.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada