Re: [ATM] Encoder roller -help

["Bob May" <rmay@nethere.com>]

I'd not run a roller but rather a rack and pinion setup as this
wil keep accuracy over the night.
The problem with a roller is that it can and will slip.  If you
put an oring on it, the radius will change, changing the rotation
rate and thus losing accuracy.
Gears and so forth are available from Boston Gear and Berg
amongst others.  Spring loading the contact so that the gear
rides firmly in the rack orother gear will tend to insure that
the slop will be at a minimun although you will thus gain a bit
of cyclic error on the order of a few arcseconds.
The best is to direct drive the encoders right off of the axis of
each axis.  The az is pretty easy as you just need to bring the
shaft up to the inside of the box and then hang the encoder above
it.  Elevation is a bit more difficult butg enclosing one side of
the bearing will allow the encoder to be hung over the axis and
thus provide the direct drive.
Bob May
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