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Equipment Discussions >> Classic Telescopes

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HBNorm
super member


Reged: 08/24/12

Loc: Huntington Beach, CA
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: Datapanic]
      #6339254 - 01/27/14 05:31 PM

Quote:

While you have movement back and forth, inspect the shaft on both ends and look and feel for small gouges caused by the set screws and file them down smooth. The Clock Drive Clutch set screw and the bearing set screws can all cause this. Remove any little bits of debris on the shaft and use a lot of Liquid Wrench to help loosen it up.

Once all the gouges are smoothed down, you should be able to bop the shaft back and forth with a rubber mallet until it eventually comes out - usually, it's best that it comes out the Clock Drive End as there are less gouges to deal with. Sometimes, the entire bearing, even though the set screws are out, will come out with the shaft. Either way, be ready to catch it once it gets loose!

In your photo, that is the entire SealMaster bearing which is pressed in to the RA Shaft Housing. There is no separate lock collar.




There were two set screws on the collar that is shown. Also, the declination end, I've taken the big allen bolt out, does the declination axis slide out by itself or will that pull the whole RA shaft out with it? Trying to figure this out without breaking anything. Have had good luck thus far...


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Datapanic
Carpal Tunnel
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Reged: 10/17/09

Loc: Tucson, Arizona
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: HBNorm]
      #6339279 - 01/27/14 05:43 PM

The Dec Shaft and the Dec Shaft Housing should already be removed. Once that big allen bolt is removed, the Dec Shaft Housing should slide off by itself. It might need a little persuasion with the rubber mallet to work it loose. It probably will not take the RA shaft with it. Once all that's done, you should have removed each pair of set screws on the SealMaster RA Bearings, then, check for those gouges and smooth them down and start working the RA Shaft out of the bearings.

Except for stuck bolts and such, this is sometimes the most trickiest part of taking the mount apart - the rest is a piece of cake


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HBNorm
super member


Reged: 08/24/12

Loc: Huntington Beach, CA
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: Datapanic]
      #6339302 - 01/27/14 06:00 PM

Got the dec shaft housing off. Are the set screws on the upper bearing a different size than the lower bearing? The lower was 5/32". Had to cut up an older Allen key. Now it looks like the upper bearing has a smaller size for the set screws?!?! Might be the same size but the aluminum decorative collar is in the way a little. On that note, how do you take the aluminum end piece off? Is that held on somehow other than being pressed on? Don't want to screw it up as I take everything apart. Sorry, lots of questions. Just don't want to screw up such a cool piece of history...

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Datapanic
Carpal Tunnel
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Reged: 10/17/09

Loc: Tucson, Arizona
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: HBNorm]
      #6339339 - 01/27/14 06:13 PM Attachment (13 downloads)

The Bearings and their set screws should be the same on both ends. Removing the aluminum end piece will really help being able to get to the set screws. The end piece is pressed in to the shaft. Sometimes it will come of by just twisting and pulling - one of those rubber jar opener things can work for that so you get a good grip on it. Other times, gently bopping around it with a rubber mallet just to break it loose and then twist and pull. Prying it off with a tool risks gouging the aluminum. For difficult cases, I have used a piece of pvc pipe angled up against the back of the collar and just tapped it while going around it to get it out.

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HBNorm
super member


Reged: 08/24/12

Loc: Huntington Beach, CA
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: Datapanic]
      #6339421 - 01/27/14 06:53 PM

Dan, thanks for the insights. I'm going to take a beer brake and then resume! How did you remove the bearings on both axes? Did you use a bearing puller?

I want to get the parts to powder coating tomorrow. Looks like my legs are natural aluminum with the dec/ra axes and pier tube in what looks to be hammer coat silver. The other parts are wrinkle coat black. Hopefully we can match it pretty closely! I'm starting to get excited!

Norm


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Datapanic
Carpal Tunnel
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Reged: 10/17/09

Loc: Tucson, Arizona
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: HBNorm]
      #6339445 - 01/27/14 07:12 PM

If the bearings don't come out, I leave them in - I think a machinists would be best to get them out. A bearing puller might work. I have only used rattle can for painting the mounts but the powder coat shop should be able to tape over the ends to protect them from the paint, not sure about the temperature factor though.

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turk123
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: Datapanic]
      #6339492 - 01/27/14 07:36 PM

Quote:

If the bearings don't come out, I leave them in - I think a machinists would be best to get them out. A bearing puller might work. I have only used rattle can for painting the mounts but the powder coat shop should be able to tape over the ends to protect them from the paint, not sure about the temperature factor though.




I agree. Do not take them out if you don't have to. Ask the powder coater if they will be safe if they are heated. I do not know that answer. I do know that those bearings are designed for high speed and lots of weight. Turning at 1 rev every day will never wear them out.


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TCW
professor emeritus


Reged: 11/05/13

Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: turk123]
      #6339581 - 01/27/14 08:29 PM

Quote:



Technically, the setscrews and large bolt are holding a lot of weight, but that weight when everything is mounted, is in perfect balance. It always amazed me how the engineering of these things were done. The castings, shaft and cradle all balance before the counter weight and ota are mounted. That amazes me how that was done.




I would challenge the idea that everything is balanced. The scope is balanced on the mount but the entire load of the scope and counter weight is off balance on the polar shaft. If you had an extended polar shaft with a counter weight then it would be possible to balance the whole thing.


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Datapanic
Carpal Tunnel
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Reged: 10/17/09

Loc: Tucson, Arizona
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: turk123]
      #6339594 - 01/27/14 08:35 PM

The operating temperature range for the Sealmaster ER-24 bearings is -20 to 220 F. Google searches show that there is a Low Temp Cure Powder Coating process that requires around 250 - 280 F... Hmmmm.

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sgorton99
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Reged: 04/30/08

Loc: Wisconsin, Madison
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: TCW]
      #6339615 - 01/27/14 08:46 PM

Quote:

Quote:



Technically, the setscrews and large bolt are holding a lot of weight, but that weight when everything is mounted, is in perfect balance. It always amazed me how the engineering of these things were done. The castings, shaft and cradle all balance before the counter weight and ota are mounted. That amazes me how that was done.




I would challenge the idea that everything is balanced. The scope is balanced on the mount but the entire load of the scope and counter weight is off balance on the polar shaft. If you had an extended polar shaft with a counter weight then it would be possible to balance the whole thing.




I was thinking the same thing as I was looking at mine.


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Datapanic
Carpal Tunnel
*****

Reged: 10/17/09

Loc: Tucson, Arizona
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: TCW]
      #6339627 - 01/27/14 08:54 PM

Quote:

Quote:



Technically, the setscrews and large bolt are holding a lot of weight, but that weight when everything is mounted, is in perfect balance. It always amazed me how the engineering of these things were done. The castings, shaft and cradle all balance before the counter weight and ota are mounted. That amazes me how that was done.




I would challenge the idea that everything is balanced. The scope is balanced on the mount but the entire load of the scope and counter weight is off balance on the polar shaft. If you had an extended polar shaft with a counter weight then it would be possible to balance the whole thing.




If the OTA is balanced around the center of the Optical Axis and also balanced longitudinally on the Declination Axis and all that finally balanced on the RA Axis, wouldn't the Center of Gravity be at the intersection of Dec and RA shafts? That point is always stationary and forward of the center of the mount, which is why one leg of a three-legged mount is always pointed north.

If the OTA is not balanced, the Center of Gravity is going to be all over the place when the OTA is repositioned on the mount to point at one object and another. Rotating the tube makes this even more apparent.

One of these days I'll get started on the article about balancing a Newtonian on a GEM....


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HBNorm
super member


Reged: 08/24/12

Loc: Huntington Beach, CA
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: Datapanic]
      #6339997 - 01/28/14 12:12 AM Attachment (15 downloads)

Well, I already spent a few hours getting everything apart. Will post a couple more posts regarding bearings next...

Edited by HBNorm (01/28/14 12:21 AM)


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HBNorm
super member


Reged: 08/24/12

Loc: Huntington Beach, CA
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: HBNorm]
      #6340003 - 01/28/14 12:20 AM Attachment (11 downloads)

Regarding Declination Axis Bearings...

How do you remove these? They seem to spin freely now that they've been degreased. Would like to get them out for powdercoating. Also, can you buy these things new? I wouldn't mind replacing bearings on both axis just to make it like new.

I plan to use Superlube for the bearings and gears like I have on my CGEM and CGE mounts when hypertuning. Is that acceptable for these mounts? I'll probably use some gun oil on the worm bear bearings and superlube on the gears in the clock drive.

Let me know if I'm going down the wrong path. Thanks!

Norm

Edited by HBNorm (01/28/14 12:22 AM)


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HBNorm
super member


Reged: 08/24/12

Loc: Huntington Beach, CA
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: HBNorm]
      #6340009 - 01/28/14 12:25 AM Attachment (11 downloads)

I was able to remove both RA Axis bearings. Can these also be bought new? They both move but they seem sluggish and one is a little rough. Since they're sealed, I cant flush the old grease out of them and repack them. Any thoughts?

On a side note... Dan, I had to use a rubber mallet to coax the aluminum end-piece off as in your picture. Thanks for the advice!


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turk123
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Reged: 07/09/10

Loc: N.E. Ohio
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: HBNorm]
      #6340171 - 01/28/14 03:38 AM Attachment (7 downloads)

Quote:

I was able to remove both RA Axis bearings. Can these also be bought new? They both move but they seem sluggish and one is a little rough. Since they're sealed, I cant flush the old grease out of them and repack them. Any thoughts?



On a side note... Dan, I had to use a rubber mallet to coax the aluminum end-piece off as in your picture. Thanks for the advice!




The answer is on the bearing itself. The bearing number. They still should be sold today. You may have to do an equivalent bearing number. I found mine easily enough just by goggling it. Also, you're right, the seal prevents you from re-greasing very well. I had one bearing that seemed a bit sluggish also. I worked in wd-40 enough to get it spin freely. You could tell it was getting into the bearing from the dirt coming out. I then used a thinner oil to lubricate. Maybe not the perfect solution, but at these speeds, it became very smooth.

You will have to borrow a bearing puller to get them out. I'm not the expert here, but I know that a press fit bearing needs equal pressure to come out. Banging on the back side sometimes just won't work. You could try soaking it in a degreaser to help.

Your doing a great job so far! Keep up the good work. Also take lots of pictures and "bag" the parts and use labels. Look at my Eli Buk Cass restoration for lots of images and what I went through. Elli Buk cass

Edited by turk123 (01/28/14 03:39 AM)


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Geo31
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Reged: 01/28/13

Loc: Kingwood, TX
Re: Just Picked Up a Cave Astrola 10" - Need Advice new [Re: turk123]
      #6340265 - 01/28/14 06:19 AM

I would think if you put the casting in the oven at say 150 for a while it should facilitate the bearing removal. I would think the casting would expand at a higher rate than the bearing's outer surface.

That said, I have no experience with this with the parts in question. I've done this with automotive piston pins however.


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dgreyson
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Reged: 11/06/12

Loc: South Carolina
Re: Just Picked Up a Cave Astrola 10" - Need Advice [Re: Geo31]
      #6340308 - 01/28/14 07:29 AM

The bearings are still available and sell for about $30 bucks if I remember right. I debated replacing mine but they didnt really need it. The Thrust bearing on the declination clutch is available also.

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HBNorm
super member


Reged: 08/24/12

Loc: Huntington Beach, CA
Re: Just Picked Up a Cave Astrola 10" - Need Advice [Re: dgreyson]
      #6340503 - 01/28/14 09:39 AM

Gregg/George/Turk,

Thanks for the input. I'll probably take the declination portion to a gear shop by my house. Hopefully they can pull the roller bearings out. I did find the SealMaster bearings. Sorry for being a dummy. After cleaning off the crud, I was able to see the make/model. Also, I re-read Jon's posts earlier as well. BTW Turk, I did exactly what you did with snack baggies and a sharpie.

I definitely have more pictures. They're on the SLR so I haven't had the chance to transfer them.

Thanks again,

Norm


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HBNorm
super member


Reged: 08/24/12

Loc: Huntington Beach, CA
Couple Restoration Questions [Re: HBNorm]
      #6341978 - 01/28/14 10:06 PM

I have a couple restoration questions...

1) Should I paint or powder coat? When thinking about the history of these mounts and how they were made, I'm now thinking that although powder coating would be more durable, painting would be more authentic.

2) Filing/sanding the leg castings. Once again, sticking to the originality of the Cave Astrola manufacturing process, should I keep the castings rough as they presently are? My anal retentive side really wants to sand the casting imperfections...especially between the webbing.

Everything is now dismantled on the mount. I plan to complete the mount and then move to the OTA. The rings and tube actually really don't need much work other than a good cleaning and polish. The interior of the OTA needs to be repainted, the finder needs a good cleaning, and the mirrors will be recoated. I lucked out on the optics side.

I'm new to the classic telescope scene and want to do this right!

Thanks for your guidance!

Norm


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dgreyson
professor emeritus
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Reged: 11/06/12

Loc: South Carolina
Re: Couple Restoration Questions [Re: HBNorm]
      #6342025 - 01/28/14 10:35 PM

I primed and painted my 12.5" Cave as I was trying to bring it back as close as possible to original. If I was to powder coat anything, I would just do the pier and legs as those seem to get the most knocks and bumps, at least in my experience. As an investment, you want to respectifully do the least you have to, to bring it back to operating condition. But as a personal possession, on the other hand, do what makes you happy. A little respectful cosmetic alteration and detailing wont make it that much more or less desireable to the serious collectors I wouldnt think.

There are artistic visionaries on CN who boldly swear by bright, glossy metallic purple finishes, and there are also die hard conservatives on here who doggedly cling to traditional white and black finishes. God loves us all, even if he does wear white.


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