Re: [ATM] roller bearing vs Slider bearings

["Don Clement" <don_clement@charter.net>]

 Arjan wrote:
> 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.

Exactly! In the real world there is no such thing as a rigid body or single
point contact. But then these are the basic assumptions of kinematics! One
can only hope to approach such idealizations.



A technique used by one bearing manufacturer to make large diameter thin
section four-point contact or "X" bearings was to use hardened wires or
"piano wire" set in slots in an aluminum ring.  The ends of the wire were
not welded or fused but left to float to make up for thermal differences in
expansion of aluminum and steel. IIR, there was an article in the old
"Gleanings for the ATM" in a '70s S&T about making large diameter thin
section bearings using hardened wire. Hardened wire could also be used
instead of hardened strip set into milled or routed slots in a telescope
mount.

John's use of polyurethane skateboard wheels was on the mark; only the
thickness of the compliant polyurethane skateboard wheels was to thick and
"squishy". A thinner layer of compliant polyurethane "tuned" for the
telescope mount parameters may just work.



Don Clement

Running Springs, California



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