Re: [ATM] Public Terrestrial Telescope: Focuser Materials &Lubricants?

["Bob May" <rmay@nethere.com>]

I'd use plastics  very sparingly outdoors due to the poor weather
resistance of most plastic materials.  Better to use sintered
bronze bearings which iwll last for a long time.
The only problem with bronze is that it has a high theft
probability and it is best to use cast iron for most of the scope
mount parts as this is the cheapest metal which won't be stolen
by some nitwit druggie.
All old materials for doing things for the outdoors but still
quite usable.
If you want to do plastic bearings, the acetel plastics like
Delrin are about the best plasticcs for the job.  Don't go for
the reinforced plastics as these  generally have glass fibers in
them to improvbe their rigidity.  Acelel plastics also do fairly
well in outdoor usage providing that the sun doesn't hit them and
degrade the plastic.
Good luck and have fun with the project.
Bob May
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