Zhumell Mod: Fix Altitude Bearing Nuts

Zhumell Dobsonian telescopes' altitude bearings are attached to the OTA (Optical Tube Assembly) by two bolts on each bearing. These bolts, however, do not have lock washers on them, and they frequently come loose, sometimes after only a night of observing. This can be frustrating and even dangerous if one of these nuts were to fall onto your primary mirror.

The solution to this of course is to add lock washers or Loc-Tite, whichever you prefer. I preferred both, so I used both. I don't plan on ever needing to remove these bolts. This is a really simple mod, and can be accomplished in less than an hour and costs nearly nothing.

1. Start by marking the tube and mirror cell with a Sharpie pen. This will ensure that when you reassemble the OTA, you will get the mirror cell back in exactly the way it came out.
   
   
2. Next, unscrew the screws at the bottom of the OTA. These hold in the mirror cell, so be careful. Once you unscrew them all, VERY carefully lift the OTA away from the mirror cell. You don't want to nick your primary mirror with the OTA.
   
   
3. This is the altitude bearing. Note the bolt I left sitting out a little bit. These are the bolts you need to remove. Once you've removed these, the altitude bearing will come off. Note on the inside of the tube, the lack of lock washers.
   
   
4. Okay, now that you've got the bolts out, simply add a lock washer in place of the stock washers. These lock washer can be found at any hardware store, such as Lowe's or Home Depot. Bring the bolt with you so you can properly size the lock washer. I had these laying around in the garage, so I didn't need to buy them. Don't put the stock washers in there with the lock washers, as that would defeat the purpose of the lock washer. You may also add some Loc-Tite to the nut if you'd like, but you'll have to wait for the Loc-Tite to dry before reinstalling the primary mirror cell. You don't want Loc-Tite to drip onto your mirror, and Loc-Tite can take a while to dry.
   
   
5. Now, reinstall the altitude bearings in the reverse order you removed them. Tighten the bolts, but don't overtighten them. This could distort your OTA. "Snug" is good enough here.
   
   
6. Reinstall the OTA onto the mirror cell, noting the marks you made in step 1 (you did do step 1, right?) Take the utmost of care not to bump your mirror with the OTA. This would be catastrophic at best. Then reinstall the mirror cell screws, and you're good to go!

This should take care of your wobbly altitude bearing problems on any Zhumell Dobsonian. The telescope shown here is a Zhumell 10" Dobsonian.

Disclaimer: I cannot take any responsibility for any damages, to you or to your property, occuring before, during, or after performing this telescope mod or resulting from any advice taken from this website. Do so at your own risk.

Clear skies!