Re: Slight Slop in the RA Axis of My Mach2



Thank you, success! Although it appeared that the pivot bolt was too LOOSE. At any rate, I jockeyed the pivot bolt around so that I got good mesh while still allowing the gears to come slightly out of mesh when pushing down on the back of the motor. With everything back together, there is no longer any “slop” in the axis.

And thank you for the quick response.


David C. Finch


From: <> On Behalf Of Roland Christen via
Sent: Friday, September 17, 2021 6:20 PM
Cc: george@...; howard@...; marj@...; karen@...; dave@...
Subject: Re: [ap-gto] Slight Slop in the RA Axis of My Mach2


Hello Dave,


Your pivot bolt might be too tight which is preventing the worm from pivoting fully into mesh. It's an easy adjustment.

Remove the outer motor box cover and set it aside with its 4 screws.

Remove the 4 screws that hold the inner cover and put those screws aside in another place, but do not mix them with the outer screws!

Now slide the inner cover back and out of the way to expose the worm assembly. You don't need to remove it entirely.


First make sure that the 3 Allen screws that hold the motor assembly to the RA axis are fully tight. If they are, then proceed with the next step:


Referring to the image below, loosen the locking screw #1 (5/64 Allen Key). Then with a 1/4" Allen key loosen the pivot bolt #2 about 1/2 turn ccw while gently pushing on the counterweight shaft in the RA direction. Gently! not with guerilla force please. It should stiffen up as the worm mates with the worm wheel teeth. Once it is in full mesh, tighten the pivot bolt a small amount and again feel the RA axis to make sure that it is meshed. You can then push down on the top back of the motor to bring the worm slightly out of mesh, then let go to allow the springs to pop the worm teeth back into mesh. The motor assembly should be able to rotate slightly in and out of mesh when you apply force to the back of the motor.


If everything feels right, re-tighten the locking screw. Then replace the inner motor cover with the shorter 4 screws (very important that you do not use the outer cover screws!!) Finish by replacing the outer cover.


Roland Christen

Astro-Physics Inc.





-----Original Message-----
From: davidcfinch9 via <DF121819@...>
Sent: Fri, Sep 17, 2021 2:07 pm
Subject: [ap-gto] Slight Slop in the RA Axis of My Mach2

Hello Ray,

I have a slight "slop" (similar to backlash) in my RA axis when I apply light pressure in rocking the telescope back in forth, which I believe is due to insufficient mesh between the worm gear and worm wheel. The "slop" amounts to about 1/64" of play at the end of the counterweight shaft. All of the RA and DEC clutch knobs are fully tightened. I removed the RA gear box cover and everything appeared to be "normal." There is no such "slop" in the DEC axis.

Is there anything that I can do to tighten things up?


David C. Finch











Roland Christen

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