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Cave Astrola Mount Restoration & Upgrade

DIY Equipment Mount Refractor Classic
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#26 gazpachosoup

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Posted 02 September 2022 - 08:01 AM

Hey, my bad!  Your RA drive is original.  The DEC drive is the Schmidt & Associates drive.  Sorry to create confusion.

My drive cover is definitely a different size.  I've seen people make others, including out of plastic.  I think I'd consider bending polycarbonate and make a new bottom and rear out of aluminum.  If you really wanted to be fancy, you could leave the PC clear.

NO worries -either way it's going to need an overhaul. Do you have a link for Schmidt & Associates? Are they still in business? A quick search didn't yield any meaningful results. 



#27 gazpachosoup

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Posted 02 September 2022 - 08:23 AM

You could substitute nylon for the cork.  Losmandy apparently uses nylon and that's what I used for me RVC-6N (you can see it in my thread).  That's another project I have to finish.  Waiting on one part that a friend was going to make for me, but a major life change had him scrambling to redo his entire art (he's a Native American artist who uses modern processes, including a CNC mill).  That put my work WAY back on the shelf, so I'm trying to find another source that isn't God-awful expensive.

Well I hope you're able to get back to finishing the project soon. Perhaps seeing this post will inspire you to do so. I had a look at your RV-6 thread and boy oh boy it has almost all the same issues that mine (RV-6) has. The only thing I don't have to deal with is the nasty black paint, but the finder holes absolutely! In fact, whomever "tried" to fix it did a real butcher job with expando foam. Here's a pic just for fun.   

 

RV-6 1.jpg

 

When I get around to it I'll cut it out and redo that section. I'll likely put a Telrad on it or a red dot. 


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#28 gazpachosoup

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Posted 02 September 2022 - 08:28 AM

RE: Part 7

 

I think those are "Pots" with locking nuts to hold their setting, not "terminals."  BTW, Pots are variable Resistors. You have two options, restore that old controller (?) or just buy a newer version that can provide the Voltage/Wattage the little motor wants.

 

 

Naturally, a newer/working one is fastest way to go, unless you like a challenge and have the skillset/time.

I do like a challenge, but I have enough to do with this rig already so I think I'm going to look for other solutions. My electronics knowledge is limited, but I may end up converting the drive systems to stepper motors - We shall see. 



#29 Geo31

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Posted 02 September 2022 - 09:54 PM

NO worries -either way it's going to need an overhaul. Do you have a link for Schmidt & Associates? Are they still in business? A quick search didn't yield any meaningful results. 

I don’t think they are in business anymore.  Best I can do is scan an old S&T ad.


Edited by Geo31, 03 September 2022 - 10:19 AM.

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#30 gazpachosoup

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Posted 03 September 2022 - 07:22 AM

I don’t think they are 8n business anymore.  Best I can do is scan an old S&T ad.

That would be great! Much appreciated! 



#31 Geo31

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Posted 03 September 2022 - 10:17 AM

That would be great! Much appreciated! 

Here you go:

RCN46RF.jpg


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#32 apfever

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Posted 03 September 2022 - 01:55 PM

Here you go:

RCN46RF.jpg

Which issue?  Month/year?



#33 Geo31

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Posted 04 September 2022 - 08:13 AM

Which issue?  Month/year?

October 1976. 

A little trivia...  I'm in a photo on p263 of that issue (which is why I've saved it).


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#34 jkmccarthy

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Posted 05 September 2022 - 12:16 PM

[...]

attachicon.gifWormgear5.JPG

 

The equipment did come with a large [DEC worm] gear, but it's unlike anything I've seen in my research. [...]

[...] I find it funny that there are clearly major parts missing like the RA setting circle and motor housings, but something oddball, like the DEC wormscrew, is there. I admit I forgot about this part in my previous posts, because the previous owner messaged post pickup to let me know that there were additional parts. Always a good thing and I'm happy that there's less to attempt to fix. 

 

attachicon.gifDECplus.jpeg

 

[...]

[...] The DEC drive is the Schmidt & Associates drive. [...]

Here FYI is a link to a previous post (https://www.cloudyni...ity/?p=11498545) commenting on worm gear tooth cross-sectional profiles, speculating that some which are triangular (i.e., with straight sides) rather than having rounded shoulders could have been cut on a lathe with a machinist's tap rather than fabricated (one tooth at a time) on a horizontal milling machine with a dividing engine incrementally clocking the worm gear blank to the position of the next tooth[*].  Although apfever's final conclusion (that I have no reason to dispute) concerning the drive on his mount [++] was it was original and not home-made, seeing these mid-1970s Schmidt & Associates ads from Sky & Telescope reminds me of our speculation (given how affordable their prices were compared to Byers and other sources for large worm gear and wormscrew sets at the time) that maybe Schmidt & Associates had commercialized the thread-cutting tap approach for making worm gears ?

 

Food for thought perhaps.   Following this thread with interest!

 

Best wishes,

 

      -- Jim

 

[*] EDIT:  Demonstrated here is the conventional method for cutting worm gear teeth:  https://www.youtube....pKuZZT6E&t=117s

 

I recall that when my dad and I used the thread-cutting tap method (or hack :-), our main concern was whether the initial passes of the tap cutting into our worm gear blank (whose circumference at the final pitch diameter we had matched to a pre-determined [integer] number of teeth for the pitch of the tap we were using) would result in more than the desired [integer] number of teeth at first, prior to the tap cutting deeper into the worm gear blank ... due to the circumference being greater at the start, before to the tap cut the "threads" down to our target pitch diameter.  But [somehow], it worked ! 

 

[++] EDIT 2: [to clarify my text that caused confusion in reply #35 below]  My text, now italicized above, was intended to reference apfever's [his] vintage "Mystery 1.5-inch shaft mount" in the thread that my post 11498545 (the one I am referring back to with the link to that previous post) was originally in regards to, which is not the same as the mount from a Criterion that apfever provided as an example in page 1 of gazpachosoup's thread here.   Sorry my reference was unclear/ambiguous.


Edited by jkmccarthy, 05 September 2022 - 06:30 PM.


#35 apfever

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Posted 05 September 2022 - 05:51 PM

I didn't quite follow that. The clutch I pictured on page one is from an Criterion and was just an example. "...the drive on his mount..." or should that be "...the drive on this mount..."? I'm not sure what is going on with the clutch on the posted scope after seeing more pictures. It looks like the gear might indeed be bolted to the plates so it can't move thus no longer being a clutch. That thing has to be taken apart to see.  Gazpacho's scope has more holes, bolts, threads, taps, and other things drilled into it than I'm acustomed to. 

 

I'm going to try that soup. 



#36 gazpachosoup

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Posted 05 September 2022 - 08:54 PM

Well I hope you're able to get back to finishing the project soon. Perhaps seeing this post will inspire you to do so. I had a look at your RV-6 thread and boy oh boy it has almost all the same issues that mine (RV-6) has. The only thing I don't have to deal with is the nasty black paint, but the finder holes absolutely! In fact, whomever "tried" to fix it did a real butcher job with expando foam. Here's a pic just for fun.   

 

attachicon.gifRV-6 1.jpg

 

When I get around to it I'll cut it out and redo that section. I'll likely put a Telrad on it or a red dot. 

Sorry for any confusion in posting this pic of my RV-6. Was posting it t show @Geo31 that it has similar issues to the one in Geo's signature. Totally unrelated to this project. 

 

I agree that the clutch on the Astrola project will need to be completely disassembled to see what in fact is going on.  



#37 Dave Trott

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Posted 05 September 2022 - 11:42 PM

I have also used a standard 1/2-13 thread-cutting tap to make a couple of worm gears. I think the technique is called "free-hobbing". Jim is correct.  Getting the depth of the threads right to make an integral numbr of threads for the diameter is a bit tricky and involves some luck. My technique was to plan ahead for what I wanted to happen and then cross my fingers that it would work out. A proper machinist would have used the techniques and (expensive) tools shown in the video. I think I blew a couple of attempts and had to make new blanks. But that part was was cheap and easy. The chewed up brass blanks were turned clean and made into knobs as I remember.


Edited by Dave Trott, 05 September 2022 - 11:44 PM.

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#38 icomet

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Posted 08 September 2022 - 11:50 AM

Here's an example of a Cave Dec drive.

 

Clear Skies.

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  • Dec drive.jpg

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#39 AstroSwift

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Posted 24 January 2024 - 01:20 AM

Hello, All,

I've been reading as many CN threads about Cave Astrola restorations as I can. A friend of a friend gave me a disassembled 8" Cave Astrola Newtonian. The badly weathered primary has the date 18 Sept 1979, SN 794026, f/6, FL 47 3/8" (sent to the Registry last month), so, close to when Cave closed up shop. From what I've read here and elsewhere, I think it was a lightweight Deluxe Model B: It has 1" shafts. The primary and secondary just got back from recoating by Majestic (looks beautiful!). While the mirrors were away, I've been disassembling the mount. The mount looks a lot like the attached picture. Note the lack of any On/Off switch on the RA drive: You just plug it in. There's no hole for a switch, either (though I may add one). The Dec axis has only a rack-and-pinion fine motion control, no Dec motor. Since taking this picture, I've been able to get off the cradle and setting circles. Despite being out in the weather, the RA drive box looks great inside (whew!).

    Now to my big question: How does one get the RA and Dec shafts out in order to clean, refurbish, and re-grease the bearings? What's involved? I've got some basic tools, but nothing specialized for bearings. As you can see, I have a lot of rust removal to do, but it's the bearings that have me stumped. All the restorations I've read seem to hop over the details of disassembling the shafts.

Thanks!



#40 AstroSwift

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Posted 24 January 2024 - 12:02 PM

The picture I dragged into my reply yesterday didn't get attached. Reading the fine print, apparently it was too big. I created a reduced size image, but CN isn't accepting it.

Since I posted yesterday, I was able to get the Dec shaft out, simply by removing the black ?delrin? bushings inside the setting circle, and sliding it out the other end. I can access the roller bearings inside. The RA shaft is still a mystery, but I'll disassemble the drive gear and clutch and see if something similar is going on with that shaft.


Edited by AstroSwift, 24 January 2024 - 02:37 PM.


#41 apfever

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Posted 24 January 2024 - 04:08 PM

Do you know if the setting circles are metal or some type of fiber press board?



#42 AstroSwift

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Posted 25 January 2024 - 02:08 AM

Do you know if the setting circles are metal or some type of fiber press board?

They're solid aluminum. I've gotten the Dec shaft out last night. I unscrewed the clock drive clutch and took the clutch and gear off the RA shaft, but it's not sliding out.

The threaded hole that's at the head of the "T", where the Dec lock knob should be (but is missing) looks mostly stripped, with only hints of threads, like a steel sleeve pressed into the cast aluminum. Looking through that hole, after clearing away some white fibrous cotton-y substance, I can see what looks like a 5/16" socket cap (Allen) screw. My Allen wrench set doesn't go that big, but that looks like it's the "key" to disassembling the RA shaft. Each day I stumble on something new.

-Ted
 



#43 bjkaras

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Posted 14 February 2024 - 10:51 PM

Analysis Part 3:

 

attachicon.gif Car1.JPG attachicon.gif Car2.JPG

 

That said, naturally I had to disassemble the pier and pier cap, to get it to fit in the car. Luckily, or unluckily, there was only one original bolt, which you'll see in the photos, I've replaced with a zinc plated hex head (I'll call it a fender bolt). It has a built in star washer pattern stamped into the underside of the head. I don't know what it's called but you get the idea. The bolts are not completely tightened down since there will be disassembly sometime in it's near future, and they will each get a nylon washer. What I found interesting was that the holes were not drilled precisely spaced and so I had to play around with the rotation of the top flange plate. You can also see two hex set screws on each side of the flange plate (beside the RA bolt) - in various states of screwing / connection. I've read that these are designed to provide a little extra clamping power, since the original locking nut typically experienced slippage. I have not tired to loosen the RA nut, but I have, preemptively sprayed WD40 on it, in anticipation of eventually unscrewing it. I will likely replace the bolt with something nicer (perhaps stainless).

The attachment of the RA tongue to the pier cap is the weak point of the Cave mounts. Even with those set screws there is still a little slippage in the axis. I’m considering drilling all the way though the tongue just so I can bolt it down more securely. Either that or adding some sort of turnbuckle. Has anyone else done anything similar to stabilize that part of the mount? 



#44 dhferguson

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Posted 14 February 2024 - 11:27 PM

Cheers,

 

Yes on the turnbuckle. I bought one at Home Depot. Here is a crop from a pic of a few years ago during my similar restoration (note the large drive covers for Byers gears). With the turnbuckle, polar alignment with accuracy suitable for AP can be made. HOWEVER, with a 67 lb tube, the mount is "bouncy."

 

Good luck!

 

Don

 

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  • 20190209_TelescopeMount.jpg

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#45 photoracer18

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Posted 20 February 2024 - 05:23 PM

Anyone seen a drive like this?

 

Cave drive..jpg



#46 apfever

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Posted 20 February 2024 - 08:48 PM

That drive was posted quite a while ago.  Did you get the entire scope? 




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