RE: ATM Equatorial platform

["Bodor, Murray" <bodor.murray@aquila.com>]

The scope is 40lbs, and yes I am planning to start with the tangent drive rod design. I picked up a 5V/0.9 degree stepper yesterday - would this be considered low-torque for this application?

One other question, if it's not too much trouble: I had planned on a poncet-style single south axis. I haven't found much in the way of recommendations for bearing sizes/recycled parts to use for this axis...but I am guessing the larger the better, for stability? I've been considering using a small (3-4") lazy-susan style bearing for this (e.g. http://www.workshopsupply.com/mischardware3.shtml) since these seem to support both radial and axial load. Are there any other commonly-available items typically used for this? 

Thanks for your comments, much appreciated.



-----Original Message-----
From: Nils Olof Carlin [mailto:nilsolof.carlin@telia.com]
Sent: Thursday, December 12, 2002 11:04 PM
To: atm@shore.net
Subject: Re: ATM Equatorial platform



> If you are planning on driving your platform with a threaded rod,
and your
> scope is not REALLY heavy, having the CG a bit away from the virtual
polar
> axis will not be a problem.  The threaded rod tangent arm drive has
a lot of
> mechanical advantage.
>
> Balance only starts to get important for heavy scopes or if you are
using
> very low torque motors

Let me add that with low torque motors, it is likely more important to
ensure low friction and no binding between the threaded rod and the
moving sled.

Nils Olof