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Astrola Clock Drive removal question

classic equipment mount reflector
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#1 DeWayne

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Posted 01 January 2021 - 12:51 PM

Hi folks, 

I'm refurbishing what seems to be a 1950s-vintage Cave Astrola 8" reflector as a fixer-upper/COVID-boredom project.  I'm at the point where I'd like to pull out the RA shaft to remove and clean up the brass setting circle (already did the DEC shaft and circle.)  In this older model of Astrola, there are no roller bearings; the shaft just slides into a tube and there is a plastic disk that serves as a bearing surface. 

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I've removed the clutch gear from clock drive, and now I need to remove the remaining piece of the clutch from the RA shaft so I can pull the shaft out, and then slide the setting circle off for cleaning.  But the clutch disk does not want to come off.  Before I start pulling on anything too hard, I'm wondering if the shaft is splined on the bottom (in which case the disk will need to pull straight off) or if it is just stuck, in which case I can work it loose eventually with wd40 and turning it. Anyone know how these things go together? 

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The Dec circle was very stiff and took several days of WD40 treatment and finally twisting with a strap wrench to loosen the old lacquer enough for removal.  I could do something on this as well, if that would work. But I don't want to start pushing and pulling without a better idea how it's put together.  

 

I know there are lots of Cave restorers on this list, so I am hoping someone has a suggestion! 

 

Many thanks,

DeWayne 



#2 ngc7319_20

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Posted 01 January 2021 - 01:43 PM

I have not personally seen one from this vintage.  But two ideas (1) are there set screws INSIDE the hollow shaft?  (2) maybe it was sweated on -- i.e. clutch ring was machined to very close fit and heated before installing -- in which case some heat might help in removing it (heat gun?).  Aluminum has about twice thermal expansion as steel, so heat would probably help.



#3 DeWayne

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Posted 01 January 2021 - 02:18 PM

Thanks! There was a set screw on the outside, which i removed.  Doesn't seem to be one inside.  Did not know about the heat angle.  Couldn't hurt to try, I guess.  

 

Based on how rough the rest of the work is, I'm going to be surprised if the end of the shaft is actually splined.  That would be more finesse than I've seen elsewhere on the mount.  This thing has more in common with plumbing than with fine machining.  Not too fussy!  


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#4 PiSigma

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Posted 01 January 2021 - 06:31 PM

I have never seen a Cave RA shaft that was splined so I doubt it is. Too costly to do that. I had a 1958 10" f/7. The hub of the RA drive was only held on by a set screw so I think yours is just stuck. The unusual thing I saw on my '58 was how they put the shaft together on the drive end. Mine had a bolt that held a short shaft extension to the main shaft. I pulled this bolt and the clutch and stub shaft came out. The stub shaft and main shaft both rode on the lower bearing, the split being right in the middle. Yours may have bearings on the RA shaft but, as you mentioned, not on the dec. shaft. The clamping bolt has little purpose except to hold the bearing.

 

 

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#5 DeWayne

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Posted 02 January 2021 - 09:24 AM

That is very interesting.   Mine does not have the bolt on the end.  I don't see a bolt hole up inside there or anything.   If there are bearings, they are still where I can't see them. Your pictures and comments are helpful,  though. Thank you!  I'll keep trying to work it loose. 



#6 DeWayne

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Posted 13 January 2021 - 10:02 PM

So... after a week or so of WD40 40 squirts, I picked up a gear-puller and heat gun from Harbor Freight.  I'd been gently tapping it with a rubber mallet and saw that it would move a tiny bit, but I had no good way to get hold of it with any of my other tools.  I applied a little heat and slowly pulled it off using the gear puller.  Handy tool, that, when it's just what you need. In any case, with the final part of clock drive removed,  I was able to pull the shaft free with no trouble.

 

There are, in fact, bearings at the top and bottom of the axle, as shown in photos above.  These were quite stiff at first, but I applied some bearing cleaner/lube and they now rotate nicely. I don't see any need to replace them. 

 

Can't wait to get this thing put back together! Should be like a whole new scope.  A lot of sanding, priming,  painting before then, though.

 

Thank you to the folks who responded with advice.  



#7 Jeff B1

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Posted 14 January 2021 - 11:11 AM

I just love refurbishing mounts.  Back to my nap smirk.gif




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