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ETX 125 RA motor bearing

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#1 EdIII

EdIII

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Posted 07 November 2019 - 07:29 PM

I have another ETX 125 jerking on right ascension movement. Many of us are accustomed to seeing this. The motor/bearing unit can no longer be bought. I know Andrew has been successful at disassembling these. I have repaired one or two, but most often I break the plastic bearing that is binding and causing the jerking. 

 

I was thinking it might might be possible to abrade and loosen the bearing in some way without removing that little plastic gear that is so difficult (for me). Anybody got any thought on how that might be done?

 

Ed

 

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#2 OzAndrewJ

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Posted 08 November 2019 - 01:52 AM

Gday Ed

Not sure what you mean here???

The big gear is a taper fit onto the worm shaft

Pulling it on too tightly can expand it and cause binding,

but i dont understand how you plan to abrade it if you cant move it out of the collar it is in.

I dont have the details, but another user was looking at using a 3D printer to make a new

collar, that could be glued onto the large flat area around the motor.

This would work for housings that had snapped the narrow collar/ring.

Never heard back if he had done it tho.

Andrew Johansen Melbourne Australia


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#3 EdIII

EdIII

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Posted 08 November 2019 - 08:23 AM

Gday Ed

Not sure what you mean here???

The big gear is a taper fit onto the worm shaft

Pulling it on too tightly can expand it and cause binding,

but i dont understand how you plan to abrade it if you cant move it out of the collar it is in.

I dont have the details, but another user was looking at using a 3D printer to make a new

collar, that could be glued onto the large flat area around the motor.

This would work for housings that had snapped the narrow collar/ring.

Never heard back if he had done it tho.

Andrew Johansen Melbourne Australia

Thanks Andrew. It seems many of these scopes came from the factory with the gear tight enough to cause fatal expansion over time. I would like to find a way to save these otherwise very useful scopes. 

 

I know you have been successful at removing these gears with your puller. I have not been so fortunate.  I think perhaps using heat and the puller, I might be able to do it. Still, the bearing/collar often breaks !! I fixed one by robbing parts and another by replacing the entire assembly.  I am getting “gun shy” with these because I know I am about to break a bearing in a scope that works, but jerks, thereby rendering it useless. In this case I just leave it jerking, but I know it is soon to break. At least I didn’t do it.

 

The 3D bearing/collar sounds good. It is out of my realm of expertise however. Perhaps someone can come up with a way to make something. If that were available, I would be willing to try to fix another one. For now, I am out of ideas since the parts are no longer available.

 

Ed


Edited by EdIII, 08 November 2019 - 08:24 AM.



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