Losmandy GM-8 Disassembly and re-greasing

I have owned my Losmandy GM-8 with Gemini 1 since the early 2000’s, probably 2005 as it was the “last big purchase” before buying my first house! 🙂 In that time I’ve cleaned the clutch plates a couple of times (to remove grease so they grip again) but otherwise not done major maintenance.

In 2022 I decided to buy a new Losmandy One Piece Worm block (OPW) and in typical amateur astronomy gear style it came with no instllation instrucitons! So, what was I to do? Disassemble until the point I could install it of course. And so ensued, a complete disassembly of the RA and Declination axis of my Losmandy GM-8, just to install the OPW. Perhaps I didn’t need to, but how was I to know without instructions.

You’ll also want:

  • lage flat works pace clear and clean of any dust, to lay out parts
  • disposable gloves
  • old toothbrush
  • at least a couple of old rags, seperate rags
  • grease for re-greasing, I use Super Lube Synthetic Grease

Below are some pictures of the Losmandy GM-8 disassembled.

The RA axis shaft removed from the housing, revealing the thrust bearing, worm cog and grease spread everywhere from the years of use.
All the parts of the RA axis of the Losmandy GM-8 laid out on the table.
The Losmandy GM-8 RA axis mount housing.
The Losmandy GM-8 RA axis mount housing shown from the pole side.Cleaned and ready to re-grease then assemble back together.

Once you have access to the inside of the RA housing you can use an old toothbrush and/or lint free rags to clean the bearings inside. The advice I read was to remove all grease so you can then regrease from scratch. I found it quite straight forward to do this.

When regreasing add only a small amount of grease. I really did use very little, probably about the same as small “serve” of toothpaste as you would put on your tooth brush.

Losmandy One Piece Worm Block

The Losmandy OPW is a single unit worm and includes the Losmandy High Precision Worm. This is an improvement over the two piece worm they previously had, but to be honest it’s not a major leap in improvement. I think the main advantage is having the high precision worm.

Being a one piece worm block it means there’s one less dimension to align when you’re getting the tension correct. But it also means it’s nearly impossible to adjust once it’s in place. I’m not quite sure how they intended adjustments to be done.

Was it worth it?

Well yes it was worth it:

  • The mount now freely moves when moved by hand, without stopping sharply due to excessive gunky grease
  • The gemini doesn’t complain about motor lag because it’s not working as hard.
  • The OPW is instaled

So, for me it was worth it, and I can see that once ever few years it’ll be sensible to do this again, though if I get around to it that often, is another thing! 🙂