Re: [ATM] Split ring bearing surface

[Andy Saulietis <iss@pvtnetworks.net>]

Gref & Ron L write:

>I am looking at making a split ring mount and was wondering for the large
>diameter bearing surface has anyone tried putting a band of polished
>stainless over it in order to produce a smooth surface. I was thinking of
>having the ends tensioned to keep the band tight.

Are you going to install this strip over wood?If so how thick is the 
stainless to be,and how wide? Do you plan to route the wood prior to 
installation?That is providing you use wood.

---

I've done this with several Dob-type scope mount, this was part of the process
required to reduce friction for the alt-az drive systems I was installing
at the time, on scopes up to 36".

A few notes on doing this:

- the bearing surfaces need to be accurately round, smooth and square.
The cast aluminum D-shaped rings on some commercial scopes were
out of round, not very smooth, and had tapered sides..these were
trued on a motorized rotary table an a carbide tipped router.

- the steel bands should be 16 gauge or thicker..thinner ones
would dent from the pressure of the rolles bearings, especially when
installed on wood.

- I built a tensioning fixture to ensure good contact between the
band & trunnion surface. A thin layer of RTV an a couple of
flat head screws were used to attach the band. The bands were made a few
inches longer than neccessary to provide an attach point for the
tensioning jig, & the exces2s cut off after the band was secured
with screws.

- a couple of flush small nails near the edge were used to
prevent the bands from slipping off the disks under load.

- I used needle roller bushings to make the idler rollers..
these ran on drill rod stock and are available in many
sizes and diameters. About $5 each at bearing supply houses.

- my drive systems used roller chain & sprockets, these were
coaxial with the band/rolles.

-using a drive roller in contact with the band also works but
added contact pressure may be needed to prevent slippage.
I've been experimenting with finely knurled hardened steel
drive rollers on steel, aluminum, and HDPE plastic disks
with encouraging results - no periodic error, slippage,
or backlash.



Andy Saulietis
ISS Enterprises
10 Milky Way
Mayhill NM 88339


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