Bronze bearing lubrication?
Posted 28 November 2012 - 04:31 AM
Obviously there is massive stiction and getting round stars with the C9 is a big challenge.
I decided to see what I could do to improve the declination axis - it runs on plain bearings (i.e. bushings).
There is a lower bushing made of PE or some similar plastic, and an upper bushing that looks like its bronze
And this is the declination axis..
Co-axial forces on the declination axis (e.g. when the scope is pointing close to the horizon) are carried by a steel sleeve and some hard plastic washers... like so:
I was able to significantly reduce the friction (and stiction) of the thrust surface by sandwiching some super-thin PTFE film between the white plastic washers. Although a better solution would be to replace the washers with PTFE equivalents (they are 2.5mm thick).
However the challenge is, when the scope is pointing close to zenith, a lot of the weight is carried by the bronze bushing on top and the plastic bushing at the bottom of the axis - and there's a very significant amount of stiction.
I tried wrapping the PTFE film around the dec shaft - the film is 1 mil thick (0.025mm) but it's too thick, the axis basically got stuck.
So what would be an alternative solution to reducing the friction? I think if even the top - bronze - bushing could be improved, the declination guiding performance would be much better.
I have tried superlube, white lithium, and silicone grease prior. None of these solutions was very good - the PTFE film on the washers is the best solution so far, but it doesn't help when the scope is pointing up.
Posted 28 November 2012 - 06:23 AM
Posted 04 December 2012 - 03:49 AM
Perhaps a local machine shop or aquaintance could give you some.
Posted 04 December 2012 - 07:15 AM
Posted 04 December 2012 - 07:33 AM
Just a thought,
Posted 04 December 2012 - 01:06 PM
But Delrin-AF costs $$$, about the same as Teflon. Ready-made polymer sleeve bearings equivalent to Delrin-AF are available from www.igus.com . Type J (?) or (?) M-250.
Or replace the PE( ?) sleeve with self-lubed bronze sleeve or tee-sleeve ? McMaster-Carr, Reid's, etc.
Posted 16 January 2013 - 08:50 AM
I got this anti-stiction Kendall 80W90 gear oil and used that. It has done nothing for the stiction.
I did notice that I am getting line contact on the bearing. Found this out because I tried polishing the bearing by putting metal polish on it and fitting the two parts together. After turning the bearing a while I noticed that the polish had been removed from a line around the bearing.
I really should not be futzing around with this mount because I got a Mach1, but it seems a waste to have it just sitting there, and selling it is out of the question due to very high shipping costs.
Posted 16 January 2013 - 04:32 PM
Posted 16 January 2013 - 05:36 PM
Cool! I just ordered some.
You could replace your plain thrust washers with thrust needle bearings for not a lot of money
Not sure what might work best on the bronze bushing , my SB lathe uses a Teflon grease in the cone assembly
Posted 16 January 2013 - 07:41 PM
It would require machining and would permanently modify / disfigure this classic AP mount.
What I've done (slightly less heretical) is ordered a scraper and some Prussian blue. hopefully I can scrape off the high parts of the bearing sleeve.
Let's see where this goes...
Posted 17 March 2013 - 03:59 PM
Posted 17 March 2013 - 06:40 PM