John Woodgate wrote:

I read in sci.electronics.design that pest3125
wrote (in . com) about
'The PEST project - completed.', on Tue, 11 Oct 2005:

It needs to be made of hardened steel for ball bearings to work well.


Try aluminium with a smear of oil. It's a little-known fact that Al/hard
steel is a non-wearing combination. See Austin 7 crankshaft main
bearings. Ball and roller races directly inserted in an Al casting(;-)

That will only be true if the balls aren't smacking into the rails with
enough force to punch through the film strength of the oil. In this
case they're probably hitting hard enough to deform aluminum directly,
I'd guess.

But yes, steel on aluminum makes a decent bearing with the right
lubrication -- take the Cox 0.049 engines as an example.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com