Re: [ATM] How to Reduce Bearing Friction

["Arjan te Marvelde" <arjan.te.marvelde@hetnet.nl>]

Don,

> Some facts on friction:
> Friction is the force (F) necessary to move an object on a surface in a
> direction that is tangent to the surface.  The Coefficient of Friction
(CoF)
> is the ratio of F to the force (W) normal to the surface (CoF = F/W) and
in

This describes the kinetic friction, i.e. the friction force you experience
when in motion.

There is another force component called static friction, or stiction. This
stiction exposes itself as a threshold you have to overcome when changing
from steady to moving state. The user experiences this as a jerkyness in
movement: the force to set the scope in motion is higher than the force
required to keep it moving.

What you ideally want is to have zero threshold, i.e. equal static and
dynamic friction. This prevents the jerkyness and increases pointing
precision. Teflon based bearings have a static to dynamic friction ratio of
almost one, the trick is to get rid of that final bit.

Ebony star apparently fits the bill. Getting the ratio down to 1 does not
require a  different placement, however it will still change the friction as
such.

 AtM

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