Jump to content


Photo

Fixing old equatorial mount

  • Please log in to reply
30 replies to this topic

#1 idp

idp

    Messenger

  • -----
  • Posts: 453
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 10 August 2012 - 09:27 AM

Hi to all, this is my first post in this forum (I have posted though in the drawing/sketching forum).

I am not a handyman at all, but a good friend of mine has given me a lot of scrap that hasn't been used in decades, and I determined to make a decent planetary telescope out of it (primary mirror is a 10" f/7).

The equatorial mount is the part that most intrigues me, the first picture shows it as I got it. Now it is disassembled as I am cleaning it, and it already looks much better (legs are already off in the picture). I wonder if anyone can identify this model? It has no maker's signature, no sign that it ever had setting circles, and seems to have been heavily modified by a previous user (lots of old electric stuff in the pier, and power outlets added). Polar and Dec. shafts' diameter is 1.5", and there are no counterweights; on the dec. shaft there is a small threaded hole towards the end, but I don't know what it is for.

I once plugged the motor drive to see if it still works: big flash and loud bang, lights out. :bawling:
OK that was not too smart. The wires' insulation is worn out and so there was a short-circuit, outside of the motor I guess. Another problem is that some screws or wing-nuts are so rusty, corroded or whatever that I cannot turn then just by brute force :mad:. Any suggestions on what I could use?

Thanks a lot folks for your help!

Ivano

Attached Files



#2 DAVIDG

DAVIDG

    Aurora

  • *****
  • Posts: 4731
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 10 August 2012 - 09:42 AM

If you look on the side of the motor, there is usually a date of when it was made, which would give a clue to who was in business making telescopes at that period.
It looks to me like it might have been made by the Spacek company. You might want to post in the Classis Telescope Forum.

- Dave

#3 planet earth

planet earth

    Surveyor 1

  • ****-
  • Posts: 1627
  • Joined: 07 Sep 2010
  • Loc: Ontario Canada

Posted 10 August 2012 - 10:05 AM

Take pictures of the legs, scope and more mount shots and closeups might help.
Looks like you have a nice project ahead of you. :)
It would be great if the RA drive works!
I'd post in Classic Forums as Dave suggested.
Clear Skies
Sam

#4 idp

idp

    Messenger

  • -----
  • Posts: 453
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 10 August 2012 - 10:37 AM

Well, of course I had other pictures... The motor is a Hurst, no year stamped on it (yes, I looked on the sides too). I am not sure it is the original one, as I said the mount seems to have been modified a lot, maybe in the 80s or 90s? I had no idea it is so old! :shocked: There is no telescope, but I will put on it a 10" f/7. Looks like it's sturdy enough.

Thanks for the quick answers

Ivano

p.s. by the way, this forum is awesome

Attached Files



#5 idp

idp

    Messenger

  • -----
  • Posts: 453
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 10 August 2012 - 10:42 AM

close-up on the AR drive.

Attached Files



#6 DAVIDG

DAVIDG

    Aurora

  • *****
  • Posts: 4731
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 10 August 2012 - 10:56 AM

Hi Joe,
The Husrt motor looks to be a 'CA' series , which I've used many times. I know you said you looked but I'm pretty sure that there is a data code on the side along with the RPM, voltage and value for the capacitor. For example the date code is usually looks like "1/72" for January 1972
Another clue is the "Black Cat" capacitor. Those were common in the late 1950's thru the 1970's.

- Dave

#7 DAVIDG

DAVIDG

    Aurora

  • *****
  • Posts: 4731
  • Joined: 02 Dec 2004
  • Loc: Hockessin, De

Posted 10 August 2012 - 11:09 AM

I did a little bit more digging and I think your mount was made was made by Coast Instruments. The mount I believe is a model "Trecker Pathfinder" Here is link to one of their catalogs, see page 35 http://geogdata.csun...coast/coast.pdf

Here is another link with pictures of the mount
http://www.skykeeper...therfinder.html - Dave

#8 roscoe

roscoe

    curmudgeon

  • *****
  • Posts: 3290
  • Joined: 04 Feb 2009
  • Loc: NW Mass, inches from VT

Posted 10 August 2012 - 06:39 PM

for your stuck bolts, you might try a penetrating fluid called ' PB Blaster' put some on each sticky bolt, from both sides if possible, wait a day, perhaps put some more on, try working the bolts a tiny bit tighter, then a tiny bit looser, and gently back and forth. and, until they suddenly start turning freely, keep up the back-and- forth motion. Be gentle, use a small pair of pliers or vise-grips, and don't reef on them, or you'll break them off, then life will get worse fast.....
It might take several days to get the oil fully into them, so be patient......

A liberal washing with paint thinner will clean all the oil off......

If you can find the rotational speed of your motor, you can likely get a new one at McMaster-Carr.com

Russ

#9 idp

idp

    Messenger

  • -----
  • Posts: 453
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 11 August 2012 - 10:03 AM

Hi Joe,
The Husrt motor looks to be a 'CA' series , which I've used many times. I know you said you looked but I'm pretty sure that there is a data code on the side along with the RPM, voltage and value for the capacitor. For example the date code is usually looks like "1/72" for January 1972
Another clue is the "Black Cat" capacitor. Those were common in the late 1950's thru the 1970's.

- Dave


Yes, the motor is a "CA" series, but I can't see any date code. All it says on the side is "MODEL CA 115V 60HZ 5W 1/2 RPM", and "HURST MFC CORP PRINCETON IND". Thanks for the links too! the mount still looks a bit different from those in the pictures. I'll send a better picture as soon as I've put it together.

Ivano

p.s. I've lived in America only for a few years, so I am abysmally ignorant about old American mounts, motors etc.

#10 idp

idp

    Messenger

  • -----
  • Posts: 453
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 11 August 2012 - 10:05 AM

Thank you Roscoe, great tips, will do. RPM is 1/2.

Ivano

#11 SkipW

SkipW

    Ranger 4

  • -----
  • Posts: 337
  • Joined: 03 Feb 2011
  • Loc: Oklahoma, USA

Posted 12 August 2012 - 07:34 PM

If the short was outside the motor, the motor itself still may work, so don't give up on that yet.

Carefully note how the capacitor and power input is wired before doing anything else. Also note the capacitance and voltage of the starting capacitor - it's probably .47 uF 250V or so, but read the markings.

Unfortunately, Hurst lists the CA model as among their discontinued lines.

The drawing for the Hurst DA/DB series looks like they have the same mounting pattern as the CA Geared (not Direct Drive), so the 1/2 RPM DB may be a possible replacement (DA is >= 1 RPM, DB is fractional RPM). Be forewarned, though - I had to replace a 4 RPM Model DA from the '60s last year, and those are still available by special order; the new one was identical to the old (except 45 years and one lightning strike newer), but it was not cheap at $180 then and most likely more now! Also, I only see the DA models listed on the table now, so the DB may no longer be available.

At any rate, if you can find a used one, either a 1/2 RPM DB or CA may work.

#12 idp

idp

    Messenger

  • -----
  • Posts: 453
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 13 August 2012 - 08:28 AM

If the short was outside the motor, the motor itself still may work, so don't give up on that yet.

Carefully note how the capacitor and power input is wired before doing anything else. Also note the capacitance and voltage of the starting capacitor - it's probably .47 uF 250V or so, but read the markings.

Unfortunately, Hurst lists the CA model as among their discontinued lines.

The drawing for the Hurst DA/DB series looks like they have the same mounting pattern as the CA Geared (not Direct Drive), so the 1/2 RPM DB may be a possible replacement (DA is >= 1 RPM, DB is fractional RPM). Be forewarned, though - I had to replace a 4 RPM Model DA from the '60s last year, and those are still available by special order; the new one was identical to the old (except 45 years and one lightning strike newer), but it was not cheap at $180 then and most likely more now! Also, I only see the DA models listed on the table now, so the DB may no longer be available.

At any rate, if you can find a used one, either a 1/2 RPM DB or CA may work.


Hi Skip,

Yes I noticed that it may be difficult to find a replacement, looks like every motor's speed is 1 RPM or above. I have attached pictures of the wiring and capacitor; black wires from the motor are not an issue, white wire goes to one end of the capacitor, red wire to the other end together with white wire from the outlet. The end of the red wire was badly exposed, so may it have touched the white wire and caused the short? :question:

I'm also finding troubles with the counterweights (none came with the mount); the diameter of the dec. shaft is 1.5", so I googled "telescope counterweight 1.5 inches" and am still shocked at what they ask for a piece of cast iron.

When I recover I'll go to Stellafane, maybe I can find something at the swap tables.

Thank you SkipW, I appreciate your input.

Ivano

Attached Files



#13 idp

idp

    Messenger

  • -----
  • Posts: 453
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 13 August 2012 - 08:29 AM

Close-up on the wiring

Attached Files



#14 roscoe

roscoe

    curmudgeon

  • *****
  • Posts: 3290
  • Joined: 04 Feb 2009
  • Loc: NW Mass, inches from VT

Posted 13 August 2012 - 09:03 AM

Motors:
Check McMaster Carr
www.mcmaster.com/
They have all sorts of synchronous motors - catalog lists 1/2 RPM 120v...... :jump:

Russ

#15 idp

idp

    Messenger

  • -----
  • Posts: 453
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 21 August 2012 - 12:50 PM

Bad news.

Back from Stellafane, I decided to finally reconnect all the wires and see if the electric motor still works (I worked on other parts of the telescope last week). While I was stripping one end of the white wire from the motor, the other one... slipped out of the motor. I pulled out the cover, two wires are accessible, the one that slipped out (lover hole in the case; it came out from the same hole as the black wire) is not. :bawling:
Game over?

Ivano

Attached Files



#16 Ed Jones

Ed Jones

    Mercury-Atlas

  • *****
  • Posts: 2673
  • Joined: 06 Apr 2004
  • Loc: Sin-sin-atti

Posted 22 August 2012 - 11:47 AM

All the timing motors I could find @ 1/2 rpm are clockwise and not reversible and I think you need counterclockwise. You might try taking the motor apart to rewire it, otherwise a stepper motor might be the way to go. Your big problem is getting everything else apart. I've seen frozen bolts heated with a torch to free them up. Good luck.

#17 gnabgib

gnabgib

    Viking 1

  • *****
  • Posts: 505
  • Joined: 05 Jun 2005
  • Loc: Fall River MIlls Ca.

Posted 22 August 2012 - 01:55 PM

Ivanho;
If you can purchase a Hurst motor for cheap you could probably "swap out" the gearbox portion and get up and running again. Check out Ebay item 290763444043 . It is a Hurst ca motor that has a 60 rpm output but the same motor side as yours. For the $10 "buy it now" it might be worth trying. By the way this is not my Ebay ad. Just trying to offer a solution.

Kevin

#18 spudrick

spudrick

    Sputnik

  • -----
  • Posts: 40
  • Joined: 22 Oct 2006
  • Loc: Heidelberg Heights, Victoria, Australia

Posted 22 August 2012 - 04:08 PM

Hello I was searching for details on a AC synchronous motor i have here it is Countercloclwise 1/60rpm. The brand is Crouzet made in France but when serching i found the USA distributor is Digi-Key at digikey.com and they have a very large range of motors.
Maybe a good source for you to find the exact replacement

#19 Geo.

Geo.

    Mercury-Atlas

  • *****
  • Posts: 2773
  • Joined: 01 Oct 2008
  • Loc: Upstate NY

Posted 23 August 2012 - 01:49 PM

The motor has to be 1/2 revolution PER HOUR or 12 per day. 1/2 RPM is 720 revolutions per day (1440 minutes = 24 hours). So the worm wheel would have to have 720 teeth and it looks a lot less than that. 1/2 RPH would only require 120 teeth on the worm wheel (1440/ 12 R/day = 120), which is what it looks like. Of course a sidereal day is shorter, but that's what correctors are for. I've got a thirty pound box of sychonus motors (who says my dad didn't leave me nut'tin) I'll took a look, the closest is a 1 RPH. I have a reversible Hurst but its off a 9" Byers that had 400-500 teeth IIRC. But moving the drive to the other end of the worm solves the rotation problem. Try that with your Losmandy!

Fairly easy to build a microprocessor controlled stepper motor driver on which you can adjust the speed. Several on line for under $50.

#20 Ed Jones

Ed Jones

    Mercury-Atlas

  • *****
  • Posts: 2673
  • Joined: 06 Apr 2004
  • Loc: Sin-sin-atti

Posted 23 August 2012 - 04:10 PM

Can't be 1/2 rph that would be 1 rev in 120 minutes plus about a 4:1 reduction gives 1 rev in 480 minutes which needs a 3 tooth gear! (1440/480) 1/2 rpm sounds right, that's 1 rev in 2 minutes and 1 rev in 8 minutes after the reduction gears. 1440/8 = 180 teeth which looks right. It probably would be a good idea to count the gear teath.

#21 Tom and Beth

Tom and Beth

    Soyuz

  • -----
  • Posts: 3623
  • Joined: 08 Jan 2007
  • Loc: Tucson, AZ

Posted 23 August 2012 - 05:01 PM

Hello Ivano,

The 1.5 inch shaft GEM like yours was indeed very common during the 50s through 70s, and other manufactures were Cave, Atlas and Meade. I'm not sure if this is still a valid Email but try Donald Rothman [newyearskid@webtv.net] for Counterweights and the Motor. If you don't have the 6 inch setting circles for the mount, they are easy to make out of wood or plastic. Matter of fact, there's a link down below in MOUNTs for making the dials.

#22 idp

idp

    Messenger

  • -----
  • Posts: 453
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 23 August 2012 - 08:26 PM

The motor has to be 1/2 revolution PER HOUR or 12 per day. 1/2 RPM is 720 revolutions per day (1440 minutes = 24 hours). So the worm wheel would have to have 720 teeth and it looks a lot less than that. 1/2 RPH would only require 120 teeth on the worm wheel (1440/ 12 R/day = 120), which is what it looks like.


Hi George,

The motor does not drive directly the worm gear; indeed, there is another reduction gear in between that is barely visible in the pictures I posted (I was interested in showing the other side). The reduction rate seems to be about 1/4, I have not counted the teeth yet as my problem is the motor; gears are now cleaned and greased and seem to fare pretty well!

Ivano

#23 idp

idp

    Messenger

  • -----
  • Posts: 453
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 23 August 2012 - 08:29 PM

Hello Ivano,

The 1.5 inch shaft GEM like yours was indeed very common during the 50s through 70s, and other manufactures were Cave, Atlas and Meade. I'm not sure if this is still a valid Email but try Donald Rothman [newyearskid@webtv.net] for Counterweights and the Motor. If you don't have the 6 inch setting circles for the mount, they are easy to make out of wood or plastic. Matter of fact, there's a link down below in MOUNTs for making the dials.


Hello Tom and Beth,

Thanks for the good tip! As for the setting circles, yes I am going to make them and there are good templates on a thread in this forum; however, posters mainly have to do with dobsonians so no one has posted a good template for an AR circle.

Ivano

#24 idp

idp

    Messenger

  • -----
  • Posts: 453
  • Joined: 21 Aug 2009
  • Loc: New Haven, CT

Posted 23 August 2012 - 08:40 PM

By the way: thanks to all for invaluable advice. I think I will still try to fix the original motor before I give up.
As for the counterweights, I still hope I can find some scrap ones around. Otherwise, I could make by filling a tin can with concrete even though concrete is not nearly as heavy as iron or steel.

Yesterday I (almost) completed the secondary mirror cell and spider, the tube is painted and I light-proofed it as good as I could. I still need a working motor, counterweights and lightshields, and then I'm basically ready to go!

Ivano

#25 Datapanic

Datapanic

    Gemini

  • *****
  • Posts: 3195
  • Joined: 17 Oct 2009
  • Loc: Tucson, Arizona

Posted 24 August 2012 - 10:26 AM

Bad news.

Back from Stellafane, I decided to finally reconnect all the wires and see if the electric motor still works (I worked on other parts of the telescope last week). While I was stripping one end of the white wire from the motor, the other one... slipped out of the motor. I pulled out the cover, two wires are accessible, the one that slipped out (lover hole in the case; it came out from the same hole as the black wire) is not. :bawling:
Game over?

Ivano


The 3-wire Hurst motors are reversible so you may not be out of business provided that the red and black wires when powered will turn the motor in the right direction. I'm not sure if you still need the capacitor between the red and white wires if you use the motor for single direction.

It may be possible to find a replacement on Hurst Motors Website that will work - it just needs to rotate at the same speed and direction as the old motor and fit its mounting. These motors are expensive! Sometimes they will show up on surplus sites as well. I found a pair of 2-rpm CA's that way for $80 or so each.









Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics