Re: ATM RE: atm pipe fittings

[Michael Juengling <mjuengling@worldnet.att.net>]

Kevin Bong wrote:
> 
> I am thinking of using pipe for my mount.  To add to Jack's question:
> 
> How smooth are threaded fittings when used in the mount.  Do the threads
> tend to wear out and get sloppy?  Is there any easy way to add variable
> friction when you are using the threads for pivots?
> 
> Kevin
> 

Kevin, I have been using a pipe mount for the last 7 years.  It has
performed quite well for me.  It has a very smooth movement and there is
little or no backlash that I can detect.  I use it for a lot of public
viewing sessions and can often keep the object centered without looking
through the eyepiece. The only problem I have with it is that it has a
little of the 'tuning fork' vibration after it is touched or slewed.  My
scope is an 8" f7 and the tube is a cedar strip/fiberglass construction
and relatively light. I used 1 3/4" pipe so it is quite strong.  

When I first constructed it I lapped the threads with some left over
grinding compound which smoothed the threads and the movement.  In
addition, dirt and dust that have got into the threads naturally (and
unnaturally) have helped to further polish the threads and the mount is
somewhat smoother now than when new. 

If the threads become loose you can just rotate the polar axis pipe to
tighten it up.  So I haven't seen any need for a variable friction
device.

It was suggested in an earlier post that a massive stand is necessary to
support the mount.  I downsized and adapted the mirror grinding stand
design I found in Texereau.  It is very sturdy and light.  I can fit it
in the  back seat of my car.  I don't have any vibration from it.

I think the main draw back is asthetic, it looks pretty crude.  Also, it
would be nice to motorize it and add setting circles.  But I haven't
come up with a good way to do either. (or even a crummy way)

I hope my 2c helps.  Good Luck.

Mike Juengling, N8ESK