Wheel Bearing Race - how much interference 1

[DavidMartin]

I'm designing a wheel hub for a 4500lbm. off-road prerunner truck with 37in diameter and 110lbm tires. I would greatly appreciate any feedback on the limits of interference recommended between the hub bore and bearing race. Based on the Force and Shrink Fit table by the American National Standard there are 5 classes of fit. At first glance a FN 2 or FN 3, having .0014"-.0037" and .0021"-.0044" Interference limits respectively, seem ideal to me. The OD of the rear bearing race is 3.715 inch. The hub material will be 6061-T6 and I'm going to guess the race is some high alloy steel, but unsure the exact grade. Thanks for any help.

 

[desertfox]

Hi DavidMartin

Probably not the answer your looking for but if it was me I would contact the bearing company and ask them for a recommended fit based on the application.

desertfox

 

[thruthefence]

There's a wiki for everything.

http://tinyurl.com/3fxvxzv

Machinery's handbook has a ton of tables for this sort of thing.

http://tinyurl.com/3vxpfm2

 

[Tmoose]

bearing races are usually 52100 steel, through hardened or close to it.

Keeping a race tight in an aluminum housing that gets warm or hot in service is difficult. At least with standard "Timken" bearings the clearance is adjusted at assembly, so a heavy interference does not use up all the internal clearance

 

[DavidMartin]

Thank you all for the great resources and info!

 

[tbuelna]

DavidMartin,

The degree of fit depends upon many things. Type of bearing, loading conditions, temperatures, relative CTE of shaft/bearing/housing materials, etc.

While you didn't mention the type of bearing, I'll assume it's a pair of tapered rollers. As Tmoose notes, it's important to install your steel cup races into the aluminum housing with a significant interference fit so that they do not become loose at operating temps. The best approach would be to thermal fit the races based on what you can safely heat the 6061 housings to without affecting the heat treat. You should be able to get at least .005 to .006 inch of interference with your 3.715 OD steel race and aluminum housing.

Also, with thermal fit races, it would be a good idea to design your hub with some provisions that will allow you to remove the race with damaging the race or hub.

Good luck.
Terry