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Question for CPC1100 owners with bearing mods.

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#1 Escher

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Posted 16 January 2013 - 01:50 PM

I was imaging last night and getting jerky images, which cloud be tied to what sounded like a jerky axis - which I believe is due to the cold last night (around 10F).. My scope lives outside... so I assume the grease is gumming up and/or the gear train is a bit tight.

So - I'm considering a teardown and re-grease.. and figured I may as well do the bearing mod while I'm in there.

I'm looking at bearings and was wondering if anyone has used Silicon Nitride Ceramic bearings? Looks like most folks just use chrome - but since I'm only planning to do this once and really want it to be as smooth as possible, the ceramic bearings would be even better.

Anyone do this? Your thoughts? Overkill?

Ive also read that the bearing channel is pretty rough - so I'm considering polishing that a bit if I can as well... At least some steel wool or something..

#2 herrointment

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Posted 16 January 2013 - 04:16 PM

I hope you get some replies as I've had some of the same issues although tracking has been fine.

I found the AZ motion on my CPC 11 to be disappointing. With the clutch loose a change in direction produces a binding action when it appears the bearings "get back in line" so to speak.

Anyway, I could make two pieces of wood rub together with smoother motion.

#3 astrovienna

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Posted 16 January 2013 - 04:40 PM

I did the bearing mod about two years ago, and have been very happy with it. My images were showing uncorrectable drifting in RA, and that problem vanished immediately. Tracking is now very good - in good conditions (ie, good seeing and no wind) I can get stars with an HFR of 1.1 arcsecs. To get much better than that I think you're looking at close to $10K in mount.

I didn't do anything fancy on the bearing replacement. Stainless steel ball bearings with machine oil, and Superlube on the gear teeth. I cleaned the groove but nothing more. I don't think the high end bearings are a bad idea, but from the results I'm getting now I don't think you need them. And I wouldn't try to buff the groove. Mine was a bit dirty but not particularly rough otherwise. If it ain't broke . . .

The key is to make sure you don't overtighten the RA axis lock nut. And you really only get this by feel. Tighten, spin it, see what you think. You want the least tight you can get but still not be able to rock the fork.

I think Celestron finally figured this out with the new CPCs, since I hear they use at least some steel bearings. I have tested another CPC1100 and the bearings on it were just terrible. I actually had to give it a shove now and then to "unlock" the bearings.

Good luck with the upgrade. Take your time and it should be no problem.

Kevin

#4 cn register 5

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Posted 16 January 2013 - 06:44 PM

We replaced every other bearing with stainless steel, this is what Celestron do for the later CPCs.

My feeling is that high performance bearings are not required, it's not exactly a fast rotation rate, or a high load.

Chris

#5 Escher

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Posted 16 January 2013 - 08:55 PM

My only thought regarding the better bearings are that they have a much better surface finish even than chrome... possibly making an even smoother rotation.

Thanks for the input everyone - I will probably do some work on the scope next week..

#6 zippeee

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Posted 17 January 2013 - 11:13 AM

I work in machining as well was on high end road racing and triathlon bikes. I will say this with certainty . . . while ceramic bearings may be smooth and hard and almost perfect, the limiting factor is ALWAYS the other surfaces (I have many stories of people spending massive $ on special bearings only to have the races wear out!). The lower bearing track is nothing more than pretty cheap, stamped steel. Don't waste your money, use good 440V bearings and you'll be golden. After I did my mod I couldn't stop spinning my scope around, it was soooo smooth.

#7 Escher

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Posted 17 January 2013 - 12:41 PM

Thanks - Thats what I wanted to hear...






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