Spacers between the Wheel Bearings [Motorcycle wheels]

[ElephantInTheRoom]

I am trying to understand what the dimension of the spacer between the wheel bearing should be. I believe because the axle tightens the middle spacer onto the inner races of both the bearings the spacer should be slightly larger than the nominal distance between the bearings so that when the axle is tightened the spacer compresses such that lateral load on the bearing goes to a minima and least bearing resistance is seen.
Question - how is this bearing toleranced, when tightening the axle is there a standard torque that is applied or is the axle tightened until the wheel is free?

 

[Tmoose]

Ball bearings?
I'd shoot for spacer length equal to the hub shoulder-to-shoulder distance within 0.001 inch. Until proven otherwise.

Is there no spec for your axle torque?

 

[ElephantInTheRoom]

Yes, these are ball bearings.
The thing is that I am actually changing the bearing off set for the wheel so I need to provide my own tightening torque and Spacer dimension.
The torque question comes because I have typically seen mechanics put together a wheel torque the axle until the wheel is free.

 

[GregLocock]

If I were designing it then I'd set the tube on the short side of the neutral length, and then specify a high torque. This turns the ball bearings into angular contact bearings.

Tolerancing such a scheme needs to consider things like camber stiffness, temperatures, and bearing life. It is non trivial, and is not a well defined calculation.



Cheers

Greg Locock


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

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

 

[ElephantInTheRoom]

I was actually more inclined towards making the spacer on the long side of the neutral length, to make sure that when the torque comes the bearing gets unloaded laterally and the ball bearing indeed function line ball bearings.

 

[GregLocock]

That will have very poor camber stiffness. That is, if you grab the rim and shake it, it'll shake. However I have never designed a motorbike axle system, I could be wrong.

Cheers

Greg Locock


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

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