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Videos of backlash adjustment for Losmandy with in-line motors?

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#1 gnarayan

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Posted 25 January 2021 - 12:57 PM

I picked up an old CG11 on CN with a bunch of upgrades. After relubing the needle bearings and cleaning up some of the old gummy grease, it's working OK in that everything functions, but its performance isn't where it should be.

 

Specifically, the Dec axis doesn't respond quickly during calibration when moving South (it's fine moving North, and seems fine when guiding), and the RA error is in the 1.5-2.5" vicinity, which is too high for this mount, and too high relative to the Dec error at 0.4-0.6".

 

I'm still waiting on the new high precision worms, having ordered them in November, but since they don't look to be shipping anytime soon, I figure I might as well clean and adjust the mount with the old stainless steel worms and see if I can improve the performance.

 

Are there any videos of backlash adjustment for Losmandy mounts with the in-line motors (not the new tucked in motors)? I've seen the new videos on the Losmandy channel, but they have a very different design for coupling the gearbox to the worm gear. I don't have a good sense of how freely the worm is supposed to rotate, and how well aligned the Oldham coupler between the worm and the gearbox needs to be. I'm hoping there's a video out there to give me a sense of this.

 

Thanks!

 

 



#2 jp071848

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Posted 25 January 2021 - 01:12 PM

I picked up an old CG11 on CN with a bunch of upgrades. After relubing the needle bearings and cleaning up some of the old gummy grease, it's working OK in that everything functions, but its performance isn't where it should be.

 

Specifically, the Dec axis doesn't respond quickly during calibration when moving South (it's fine moving North, and seems fine when guiding), and the RA error is in the 1.5-2.5" vicinity, which is too high for this mount, and too high relative to the Dec error at 0.4-0.6".

 

I'm still waiting on the new high precision worms, having ordered them in November, but since they don't look to be shipping anytime soon, I figure I might as well clean and adjust the mount with the old stainless steel worms and see if I can improve the performance.

 

Are there any videos of backlash adjustment for Losmandy mounts with the in-line motors (not the new tucked in motors)? I've seen the new videos on the Losmandy channel, but they have a very different design for coupling the gearbox to the worm gear. I don't have a good sense of how freely the worm is supposed to rotate, and how well aligned the Oldham coupler between the worm and the gearbox needs to be. I'm hoping there's a video out there to give me a sense of this.

 

Thanks!

You might want to inquire over on the Losmandy and/or Gemini II Groups.io user groups, well worth joining.  Lots of very experienced users over there who may be able to point you in the right direction.

 

https://groups.io/g/...dy_users/topics

https://groups.io/g/Gemini-II/topics


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#3 gnarayan

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Posted 25 January 2021 - 01:18 PM

You might want to inquire over on the Losmandy and/or Gemini II Groups.io user groups, well worth joining.  Lots of very experienced users over there who may be able to point you in the right direction.

 

https://groups.io/g/...dy_users/topics

https://groups.io/g/Gemini-II/topics

Yes, I'm on those boards and went through their archives, and actually mailed Tanya and Scott back in Dec (no response, sadly). I did pick up a 12V - 15V transformer from Michael Herman based on a post there as well, to eliminate power supply being the issue with the tracking. Figured I'd try posting here because of the larger audience.



#4 SMigol

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Posted 26 January 2021 - 06:45 PM

For dec backlash issues, look at these things:

 

Remove the cover on the dec worm and do centering moves - look to see where the backlash may be.

 

It can be between the gear box and the worm which can be overlooked:

 

1. make sure the set screws are tight on the oldham coupler - these can work loose over time.

2. make sure the nylon insert is tight inside the oldham coupler.  These can also age over time and work loose.

 

The worm can have end-play which can be seen by the gear sliding back and forth in the bearings. 

 

This can be compensated somewhat by running with the dec run off balance to introduce a bias.

 

The mesh of the worm to the ring gear can be out of adjustment, allowing the ring gear to slide back and forth.  This may need to be adjusted seasonally as the metal expands and contracts with temperature.


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