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Clock drives

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#1 rogue river art

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Posted 06 April 2019 - 10:28 PM

Let's see some pictures of Unitron weight driven clock drives. There is lots of discussion about Unitron telescopes and pictures but not about the clocks. I have my own which is home built clone but would like to get some discussion going on the original clock.


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#2 rolo

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Posted 07 April 2019 - 07:59 AM

You should post a picture of your home made clone drive....I have a Unitron 160 in need of weight driven drive and tray but I'm afraid the price of a used may not be worth the expense.

 

 

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#3 Richard O'Neill

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Posted 07 April 2019 - 09:44 AM

 This link displays lots of pictures of Unitron drives.  http://tinyurl.com/y5ohou67

 

 However, as Rolo said, it would be far more interesting to see the gravity drive you've made. To me that's a significant accomplishment that I've only dreamed about replicating.

 

 Three years ago twin home made refractors with their gravity drives were displayed at Stellafane.

 

Homemade Refractor with Gravity Drive
 
Gravity Drive 1

 

 

.


Edited by Richard O'Neill, 07 April 2019 - 10:08 AM.

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#4 rogue river art

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Posted 07 April 2019 - 11:49 AM

Here is a closeup of the clock I made from a picture of a Unitron with a few changes.DSCF4028_preview.jpeg


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#5 Richard O'Neill

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Posted 07 April 2019 - 12:06 PM

 Beautiful workmanship! Is your drive currently used with a telescope? The Unitron drives I've seen run for about an hour before the weights need resetting.

 

 I once thought of adapting a wind up phonograph motor (with spinning ball governor) to a small telescope but never got around to completing it. So many projects, so little time. I'm sure you understand. flowerred.gif 



#6 rogue river art

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Posted 07 April 2019 - 12:49 PM

It does run my 4" refractor for about twenty minutes. It's on the scope in my profile picture.


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#7 TOM KIEHL

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Posted 07 April 2019 - 01:31 PM

 

 Three years ago twin home made refractors with their gravity drives were displayed at Stellafane.

 

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#8 rolo

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Posted 07 April 2019 - 01:35 PM

Here is a closeup of the clock I made from a picture of a Unitron with a few changes.attachicon.gif DSCF4028_preview.jpeg

Impressive work!


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#9 Richard O'Neill

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Posted 07 April 2019 - 02:26 PM

Thanks for the closeups, Tom. Those scopes were absolutely beautiful beyond expectation. Wish I could have observed through them but I had to get up early for an all day drive home.


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#10 Richard O'Neill

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Posted 07 April 2019 - 02:41 PM

"It does run my 4" refractor for about twenty minutes."

 

 I wonder if the run time could be extended using pulleys like the drive shown at Stellafane? I suppose it would require a heavier weight but the extra time could be worth it.



#11 rogue river art

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Posted 07 April 2019 - 04:38 PM

It already has one set of pulleys and the weight is about ten lbs and I don't want more . The weight is solid polished bronze like the EQ mount.



#12 Richard O'Neill

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Posted 07 April 2019 - 06:03 PM

".. the weight is about ten lbs and I don't want more."

 

 I understand. The older I get the heavier weights become. wink.gif 



#13 Spectral Joe

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Posted 07 April 2019 - 06:50 PM

 Beautiful workmanship! Is your drive currently used with a telescope? The Unitron drives I've seen run for about an hour before the weights need resetting.

 

 I once thought of adapting a wind up phonograph motor (with spinning ball governor) to a small telescope but never got around to completing it. So many projects, so little time. I'm sure you understand. flowerred.gif

Something like this?

Sorry about the busy background, shooting the other way got a lot of sun glare from the windows.

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#14 rogue river art

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Posted 07 April 2019 - 08:07 PM

DSCF4536.JPG No. Looks good but very robust. Maybe for opening a draw bridge? My cables and pulleys are much lighter in weight. Shown is a pic of the telescope mount.


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#15 rogue river art

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Posted 07 April 2019 - 08:09 PM

Something like this?

Sorry about the busy background, shooting the other way got a lot of sun glare from the windows.

Those are some serious weights there. What are you going to drive with that clock?



#16 Spectral Joe

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Posted 07 April 2019 - 09:32 PM

It's been used to drive a 4 inch refractor, the gear ratio was chosen to give a long time between windings (45 minutes) so more weight was required. It turned out to have more power than I needed. 25 pounds of steel in the main weight, 5 pounds in the counterbalance weight. It would have driven my old 6 inch refractor just fine. Huygens endless chain drive, so winding does not interrupt the drive.


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#17 rayden68

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Posted 07 April 2019 - 11:19 PM

I am always blown away by the talent and skill of my fellow astronomy enthusiasts. real talent on display!bow.gif  


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#18 Richard O'Neill

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Posted 08 April 2019 - 08:33 AM

"Something like this?"

 

 Wowee!!! I had thought of using the phonograph spring for power but you've taken the idea well beyond that. I marvel at your ingenuity and workmanship. The uninterruptible endless chain drive is superb! waytogo.gif 



#19 Richard O'Neill

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Posted 08 April 2019 - 09:11 AM

 Returning for the moment to the original request, there are two sizes of Unitron weight drives (see link for pictures) plus minor variations in the linkages and mount attachment hardware. Internally they appear essentially the same. Also noted is the presence or absence of a Unitron (or Polarex) logo on the front panel of the housing.  https://www.unitronh.../weight-drives/


Edited by Richard O'Neill, 08 April 2019 - 09:13 AM.


#20 rogue river art

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Posted 08 April 2019 - 02:56 PM

 Returning for the moment to the original request, there are two sizes of Unitron weight drives (see link for pictures) plus minor variations in the linkages and mount attachment hardware. Internally they appear essentially the same. Also noted is the presence or absence of a Unitron (or Polarex) logo on the front panel of the housing.  https://www.unitronh.../weight-drives/

Very good pictures. If I had detailed pictures like that when I built my version It would have been much easier. I spent many hours with magnifying glass studying two photos that I took of a clock someone else had. Didn't know there were two sizes.Thanks.



#21 clell777

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Posted 14 August 2019 - 10:19 AM

Picked up one last week, working great. Really nice work on the custom clocks you guys pictured.
8219A0C3-0308-4F2F-8081-7D2F033525A8.jpeg
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#22 photoracer18

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Posted 14 August 2019 - 03:04 PM

Wish I still had some photos of the Goto gravity drive that powered the RA in the 12.3" Goto Cassegrain we got from the NASA warehouse for the new astronomy club at NSA in 1973. The weights ran right down the center of the 300# 2 piece pedestal that carried the mount.


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#23 G-Pa Es

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Posted 30 June 2020 - 06:01 PM

It's been used to drive a 4 inch refractor, the gear ratio was chosen to give a long time between windings (45 minutes) so more weight was required. It turned out to have more power than I needed. 25 pounds of steel in the main weight, 5 pounds in the counterbalance weight. It would have driven my old 6 inch refractor just fine. Huygens endless chain drive, so winding does not interrupt the drive.

 

Where can I get more details on a drive like this? Has anyone ever seen one driven by a spring instead of weights? TIA



#24 rogue river art

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Posted 30 June 2020 - 09:52 PM

For your infomation there is on display at the Mt Wilson observatory a clock drive that looks like the Unitron clock just many times bigger



#25 luxo II

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Posted 30 June 2020 - 11:39 PM

Where can I get more details on a drive like this? Has anyone ever seen one driven by a spring instead of weights? TIA

See for example http://www.theskyscr...ial-observatory and page 68 of this link "https://ui.adsabs.ha....63B/abstract" 

 

They're almost always driven by a falling weight - not a spring. The weight is tied to a wire or chain wrapped around a cylindrical drum so it provides a constant forces (torque) to drive the RA worm and a  spinning governor which regulates the speed precisely. The governor effectively regulates the speed the weight can fall - hence the other name for this mechanism - an "escapement".

 

If a spring was used, the torque would not be constant - maximum when the spring was would up, and declining to nothing as the spring reach maximum extension. This would not be sufficient to maintain a constant tracking speed.

 

The governors used typically employed 2 or 3 weights designs to lift as the speed of the governer increases, as they rise this causes a very slight contact with a fixed plate which acts as a slight brake to slow it. If on the other hand the governor slows to the point the weight drop a little, the torque of the weight causes it to accelerate again.

 

When well-made by an instrument machinist, the result is a surprisingly precise speed control.

 

NB at the start of the observing session there is usually a way to disengage the gears between the drum and the RA worm and the governor, and wind the weight up with a crank handle. Remove the handle and re-engaging the gears sets it in motion.


Edited by luxo II, 30 June 2020 - 11:50 PM.



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