ATM bearings, part II

[tkrajci@san.osd.mil]

>From: "Kreig McBride" <astroguy@nas.com>

>For my particular project, I am looking to mount an 8" refractor f/13.3 
>and
>wanting the mount to be ridged, accurate, smooth, easy to assemble for 
>some
>portability and esthetics.

>Pillow block mounted bearings
>should work will but agian, not fall into the esthetic category.

>So for now, I am looking at sintered bronze bearings and/or tapered 
>rolller
>bearings and 2"+ shafts for this project.

As you have said, mount stability/stiffness will be very important for 
this large refractor.  Do not forget to keep stiffness in mind in all 
mount components.  You have mentioned shafts, but don't forget shaft 
housings.  Mounting pillow blocks on a plate is easy and fast...but that 
flat plate is not anywhere near as stiff as a tubular (square or round) 
shaft housing.  Also think 'stiffness' where the dec. shaft housing 
connects to the r.a. axis, and where the dec. shaft joins the refractor 
tube, and where the r.a. shaft housing connects to the 
tripod/pier/whatever.  Don't forget to analyze drive stiffness (or brake 
stiffness) as part of your design...a small worm gear is not very 
stiff...especially for a big refractor.

If you get around to it...posting some drawings somewhere will help a good 
deal.

I hope this helps,
Tom Krajci