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CPC1100 Az Bearings Question

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#1 MarMax

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Posted 02 March 2021 - 12:46 PM

I have what I believe is a 2014 CPC1100 and I'm noticing a very slight hitch in the giddyup of the Az movement. Is there a way aside from taking the base apart to know if I have plastic bearings or the plastic/steel mix of bearings?

 

Based on what I feel in the Az movement I'd say that there is a few plastic bearings with flat spots, or maybe some debris in there. It's very slight but noticeable as you rotate the base and as you would expect, more noticeable with more weight.

 

Should I just go ahead and take the base apart and replace the bearing with steel?



#2 jl09

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Posted 02 March 2021 - 02:57 PM

Based on extensive internet research smirk.gif, my understanding is that the base model (CPC 1100 SCT XLT GPS) has the plastic bearings. Some of the other Celestron "higher end models" have the mix of plastic and steel. 

 

I don't know when mine was manufactured, but it was purchased new in 2019. It sounds like your model is the same as mine, probably just older. I'm not sure what year they started installing only plastic bearings.

 

I had the same concern that you have. The only way I could know definitely was to take it apart, unfortunately.

 

I ended up replacing the plastic ball bearings with all stainless steel, mostly as a pre-emptive measure / upgrade. 


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#3 MarMax

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Posted 02 March 2021 - 03:51 PM

Great response, so thank you jl09waytogo.gif

 

We have the same scope so I'll just go pick up some bearings at McMaster-Carr and do the swap.

 

I see you have a wedge so this was a "must-do" thing for the extra loading on the Az bearings. Did you notice the improvement after the plastic/steel replacement or was it more preemptive?



#4 jl09

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Posted 02 March 2021 - 04:43 PM

Thanks. To answer properly, probably a little more detail would help.

 

Last fall, I was noticing non-smooth motion from the mount (on the wedge). Especially noticeable when using PHD2 and guiding at long focal lengths. I was never sure if it was the onset of cold weather (lower temperatures), or a problem with the bearings. In any case, when I took the mount apart, I did find that the bearing raceway was "dirty", and what appeared to be some small specks of plastic that were embedded in the grease. Also, probably due to issues casting the metal base (the bottom piece), the bearing raceway had a few "ruts" with paint in them. When I cleaned them out, I could see that plastic balls running over those ruts would not be good, and they would eventually wear down. Also, the grease Celestron used seemed kind of "sticky" to me. I figured I'd try to address these problems. 

 

After another internet research project to figure out how to do it and what to use, I selected the ball bearings, and type of grease. I ended up ordering the "Tight-Tolerance Hardened 440C Stainless Steel Ball, 1/4" Diameter, 3 Packs of 50" from McMasterCarr, and I used the SuperLube Multi-Purpose Synthetic Grease. There are many opinions out there about these choices, hope I made the right ones! And, I'm hoping the newly installed stainless steel balls will be able to roll over the ruts without an issue. Also, adjustment of the main nut that holds down the top of the base and thrust bearing was more of a pain than I bargained for. It took me many iterations after the bearing replacement to get the tightness "just right". Oh, and I cleaned and re-greased the worm gear and the az gear. 

 

Anyway, it was an interesting winter time project. I've been able to use it a few times, and the mount operates much better; very smooth. Hard to tell yet whether I'm getting decent guiding performance, since the few times it's been clear this winter, it's mostly been windy. And, maybe the much colder temperatures have an effect as well. 

 

In any case, I'm grateful to the many people who posted about their experiences on CN, all that info really helped. 

Sorry for the long answer, hope that helps. 



#5 MarMax

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Posted 02 March 2021 - 08:30 PM

More excellent information so thank you!

 

I'm going to try the Tight-Tolerance Multipurpose 304SS ball bearings with a Rockwell C25 hardness. Not that it makes any difference but I'm thinking the scope is aluminum, which is soft, so I'll try the least hard stainless steel bearing. And I'll probably use the same grease as it has been recommended quite a bit.

 

It will be interesting to see how things look once I get the base apart. The paint filled ruts do not sound like a good thing if smooth operation for AP is your goal. I don't think my scope was ever used on a wedge so there should not be any abnormal wear on things. It's possible that what I can feel in the Az movement is more of those paint fill ruts. undecided.gif

 

This all has me wondering if there is some maintenance that the Alt system may need.



#6 jl09

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Posted 02 March 2021 - 08:58 PM

Right, there was nothing I personally could do about the ruts, except maybe fill them with epoxy. But I'm sure if I had done that, then the final finish would not have been smooth anyway. Anyway, my az motion is noticeably smoother now, so I'm hoping it will give me better performance than before. 

 

Actually, it ended up that one of my Alt fork arm nuts was a bit loose too, and one of the washers had slipped a bit out of position. So I had to make sure everything was lined up and tightened properly. 

 

Good luck with yours! 


Edited by jl09, 02 March 2021 - 09:16 PM.


#7 Michael_Swanson

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Posted 02 March 2021 - 09:21 PM

As far as the "how to", on this page of my website:

https://www.nexstars...OddsEndsCPC.htm

 

See Gary Bennett's article "Disassembly of the CPC Azimuth Assembly and Replacement of the Stock Nylon Bearings".

 

Best regards,

Mike Swanson
https://www.NexStarSite.com


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