Re: ATM Manual/motorized combination dobs

[Andy Saulietis <iss@pvtnetworks.net>]

Hi Colin,

>        Has anyone built, designed, thought of or have details of a
>Dobsonian built as a motorized unit ( following Mel Bartels principles)
>that could be changed quickly and easily in the field to a manual Dobsonian
>(following Kriege and Berry)?
>        I can see how Telfon pads could be shimmed up (following Chuck Shaw
>and others) or mechanically moved up to take over from the alt and az
>bearings and drive shafts. But how could the bearing contact  surfaces be
>changed from steel to Formica to get the correct 'stiction'? Or can you
>drive my size of scope directly using Formica surfaces or get the correct
>stiction using metal drive surfaces and  a slip clutch in the final drive? 
>        I am building a 14" f 5.3 at medium to light weight but not ultra
>lightweight. I am worried that on some occasions I may not have the
>facilites nor time to run the telescope fully computerised and motorised.
>Please forgive me if this is an obvious or oft asked question - I have
>tried a  search of the archives.

The system I designed and sell, in the visual version, uses 1/4" roller
chain wrapped around a metal edged plywood disk, engaged to a small sprocket
that is driven by the stepper via a small reduction gear. An adjustable idler
sprocket allows the friction to be adjusted. The alt/az bearings use ball
bearing
rollers/metal edged disks so the drive system sees only a small amount of
friction. The steppers I use are only for polar tracking, if higher speed
motors are used with the Bartels system the drive can be used manually or
fully motorized with no change in configuration.


Andy Saulietis
ISS Enterprises
39 Silver Fox Trail
Mayhill NM 88339
505-687-3067 voice
505-687-3021 fax, call voice or e-mail to set up
e-mail: iss@pvtnetworks.net