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Damping Grease, Ball Bearings,.and the 2-Speed GSO focuser

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#1 Phaenomena

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Posted 05 December 2021 - 07:23 PM

I just acquired a GSO 2-speed linear bearing Crayford, and have tweaked it so it's reasonably smooth and the "clicking" is now much subdued in the two speed mechanism. But ... I'm curious if I can get it smoother.

I was considering coating the ball bearings in the two speed mechanism with damping grease to smooth out the motion. I have some Nyogel 767a that I've used on my rack and pinion focuser (and on an alt az mount) to great effect - I hardly have a reason to replace the plastic focuser on my Z130 anymore. Would damping grease negatively affect the ball bearings? The stuff is super thick, and I don't want to clog it, just smooth it out...

#2 markb

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Posted 05 December 2021 - 07:38 PM

I had a used GSO dual speed that had the click sensation. Disassembling and regressing didn't do the trick nor did careful adjustment.

 

IIRC I finally found tiny irregularities in the shaft.

 

I believe it had fallen or been overtightened, and the irregularities (flats?) caused the sensation. It went back to the seller (not an AM or CN transaction), and I sourced another.

 

I doubt grease will do it for you, bit I also see not reason not to try. If it reduces contact friction too much (I assume this could happen) it is easily reversed by cleaning.

 

My GSO dual speeds, including an older pre-dual with the dual knobs and rod added (the missing attachment screw actually can be ignored) are silky smooth.


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#3 Phaenomena

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Posted 08 December 2021 - 11:49 AM

Thanks for the insight. I tried the Nyogel, and it kind of worked, but how much better than the super lube I put in before I don't know. I briefly had it adjusted perfectly - it was super smooth. But with the stickier damping grease, I think the extra force required to turn the pinion caused the nut holding the two-speed pin to become too loose. I had to do a lot of tweaking to get the tension just right, and but it's mostly okay now. Coarse focus is a little rough, but the fine focus is really quite smooth.


Edited by Phaenomena, 08 December 2021 - 12:13 PM.


#4 Jon Isaacs

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Posted 08 December 2021 - 01:11 PM

My experience is similar to Mark's. I have worked on a number of focusers and when a two speed is notchy, it's because there is damage to one of the surfaces.  And I have tried all sorts of things, polishing the various surfaces, replacing the balls, nothing really worked.. 

 

The good thing about GSO two speed focusers is that they all seem to use the same two speed microfocuser and you can purchase a two speed upgrade kit that includes the micro focuser for $60 from AgenaAstro.  Of course they are currently out of stock but someday.

 

https://agenaastro.c...pgrade-kit.html

 

Jon


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#5 Phaenomena

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Posted 08 December 2021 - 01:59 PM

My experience is similar to Mark's. I have worked on a number of focusers and when a two speed is notchy, it's because there is damage to one of the surfaces.  And I have tried all sorts of things, polishing the various surfaces, replacing the balls, nothing really worked.. 

 

The good thing about GSO two speed focusers is that they all seem to use the same two speed microfocuser and you can purchase a two speed upgrade kit that includes the micro focuser for $60 from AgenaAstro.  Of course they are currently out of stock but someday.

 

https://agenaastro.c...pgrade-kit.html

 

Jon

Good to know. Again, I've got it functional, and with a mostly smooth fine focus it's better than the rack and pinion focuser with a peanut butter jar lid screwed onto one side that I was using before! I'll keep an eye out for the upgrade kits down the line.



#6 Phaenomena

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Posted 08 December 2021 - 02:08 PM

I had a used GSO dual speed that had the click sensation. Disassembling and regressing didn't do the trick nor did careful adjustment.

 

IIRC I finally found tiny irregularities in the shaft.

 

I believe it had fallen or been overtightened, and the irregularities (flats?) caused the sensation. It went back to the seller (not an AM or CN transaction), and I sourced another.

 

I doubt grease will do it for you, bit I also see not reason not to try. If it reduces contact friction too much (I assume this could happen) it is easily reversed by cleaning.

 

My GSO dual speeds, including an older pre-dual with the dual knobs and rod added (the missing attachment screw actually can be ignored) are silky smooth.

Can I ask which shaft had the irregularities? The main pinion, or the fine focus one?



#7 markb

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Posted 08 December 2021 - 05:47 PM

It was almost 2 years ago so I'm not certain.

 

I'm pretty sure it was the long fine focus shaft that is part of the dual conversion (I've done the GSO conversion using the Agenda one linked by Jon, the knob includes the thin shaft as I recall) OR an irregularity within the dual knob assembly itself. It was partially disassembled during the attempt to tune it.

 

EDIT I think the balls in the dual head had dinged the internal shaft assembly.

 

But it was bought used at close to full used price so I required a return by the seller instead of trying the dual kit shaft at my expense. My GSO conversion was with my west coast stuff so it was not around to try.

 

The GSO dual upgrade is a breeze to do IIRC, likely done 3 years ago on my west coast focusers.

 

The plain, 'just knobs' GSO knobs carried by Agena solved a couple of other focuser issues, incidentally. They offer a knob stalk length long enough to be compatible with a few uses Astro and nonastro, and come in 6 an 8 mm hole versions. Their machining is quite good. I am very happy with the duals, including my reflector dual speed sold under the Orion name.


Edited by markb, 09 December 2021 - 01:02 PM.


#8 Steve Cox

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Posted 08 December 2021 - 10:00 PM

Here is the best guide I know of on servicing and tuning up the GSO focuser - http://polluxchung.c...o_crayford_fix/ .  In it he mentions greasing the bearings, perhaps there's something in there that would help you.  Personally, it seems like if the grease is compatible with the parts and is stable enough not to flow to where it's not wanted, I can't see it hurt.  If anything, you could always clean it off if you don't like the result.




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