anti-slip "stop rings" on 1968 Newt hardware

My stock of 1968 Optical Craftsmen vintage supplies includes two "anti-slip rings" or stop rings. These prevent the tube from slipping forward or backward.

They are a bit trickier than they look. They don't make 100% contact against the tube rings; they only turn against the nylon screws that stick out from the tube rings.

yesterday I got everything balanced just right and tightened the stop rings down with each one touching the tube ring above/below it.

This turned out to make it very difficult to rotate the tube. If two rings are making contact against the nylon screws you have twice as much friction.

So I had to put a little play into the adjustment. Now the rotation is easy but the tube is capable of about 1/4 inch movement. I might be able to narrow down the play but the stop rings are not 100% in the same plane.

Anyhow I think this is a very antique consideration. I'm not sure anyone will know what I'm talking about....

Greg N
(similar post on CN)

Attached Image:

I'm not very familiar with OC. What contacts the telescope
tube at the main rings? Are they mounted with felt? Rollers?
Or is there an inner metal ring screwed to the tube like
the Cave rotating rings? Cave had inner and outer rings with
Teflon plugs between them running in a machined track.
It worked pretty well, once the tension on the plugs was
set properly.

I expect if things weren't in the same plane, the stop rings
could be squeezing the main rings as it rotates. Probably
the 1/4 inch "play" is a complete non-issue.