ATM Roller bearing material

[Chris Westland <westland@uxmail.ust.hk>]

Hi Mel & Bob:

I am in the process of starting a stepper driven Dobsonian, with Hurst
steppers (initially using a Dob Driver II that I purchased, but
ultimately moving to a computer controlled setup) and am interested
again in eliciting your experiences and thoughts (and those of the list
members) on the bearing material.

I am planning on using 1.5" stainless steel rollers on stainless steel
bearings 24" in diameter (both Alt and Az).  Bob Pfaff in an earlier
correspondence had suggested that he liked Nylon on Stainless best.  I
had even considered using roller skate wheels, but someone on the list
thought these made a scope feel "mushy."  My one concern with stainless
on stainless is that when hand slewing the scope, whether the metal on
metal will make a noise somewhat akin to fingernails on blackboard.  I'm
presuming that you position your scope simply by dragging it by hand to
where you want it to point, and then fine positioning with the computer
(am I wrong??).  I was afraid that with nylon, I might get a mushy feel
also, as well as have the problem of a sticky sort of bouncing when I
had slew.  Not having used a scope like yours', I'm not sure what to
expect.  I have also found a nylon composite here in HK that I am told
is a rigid as steel ... perhaps with composites I might get the best of
both worlds.

Any words of advice before I finally commit myself to a particular set
of materials.

Thanks

-c



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Chris Westland
Hong Kong University of Science & Technology
Clear Water Bay, Kowloon, HONG KONG
Tel:                 ++852 2358 7643
Fax:               ++852 2358 2421
E-mail:          westland@uxmail.ust.hk
WWW:           http://home.ust.hk/~westland/westland.htm
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