Re: ATM Aluminum, Split Ring, Astrograph

[Ak55c@aol.com]

Dave,
My personal suggestion for the highest quality split ring mount is to use 
mild steel plate with a stainless steel ring welded to the edge for contact 
with the rollers.
     The steel plate can be very thin (3/32" to 1/8") because the stainless 
ring
(1/4" to 1/2" thick by 1"+ wide), acts  similar to the flange on a steel I 
beam
and resists deflection.  Large holes can be drilled in the steel plate to 
further 
reduce the weight of the unit without significantly affecting stregnth.  The 
stainless flange provides a wide contact area to the rollers which will 
minimize 
deformations to the contact surfaces.  Rollers should be 1" or larger 
diameter and
preferably a harder stainless alloy for best wear characteristics.  The ring 
can 
be ground round  by setting up a temporary bearing point in the center of the 
ring and using a grinder.  I am currently in the final grinding stage of a 
62.5" diameter split ring and would be glad to share more information with 
you or any other members.  A great book for info on these types of mounts is 
"robotic observatories" by Genet and Hayes.  These type of mounts are used at 
the Fairborn observatory for remote astronomy.  I can get  the web address if 
anyone is interested. They have some good photos.

good luck,
Scott Seickel