[ATM] roller bearing vs Slider bearings

[Arjan te Marvelde]

Some thoughts about contact deformation.

The contact "singularity" does not exist in reality, but is depending on the
excerted force and the strain/stress curve (i.e. Youngs' modulus, E). The
contacting surfaces will deform until the contact area is large enough to
establish an equilibrium. As long as you stay away from the yield strength
of the material the surface shape will restore itself.

As Don suggests you might want to go for a hard, high-E material and get
little deformation for a certain pressure. This implies that the contact
pressure will be large and a high yield strength is required. This is the
steel on steel route, which will indeed serve well as a stone cruncher.

As an aternative, you can go for a low-E material, such as rubber. You get a
lot of deformation but also a low contact pressure. Therefore the
requirements on yield strength are relaxed . No stone crushing either, but
as a consequence less positioning accuracy.

Some design issues:
What would be the accuracy required in an azimuth bearing?
How much will the contact forces vary?
What is the amount of deformation related to bearing diameter?

Cheers,
   Arjan

> Even hard-anodizing is only a few mils thick and does not always stand up
to
> extreme stress of the line or point contact "singularity" of a roller
> bearing. I prefer to use hardened stainless steel strip bonded to aluminum