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Hurst motor repair?

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#1 ccaissie

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Posted 06 August 2014 - 08:58 PM

I've separately burned out two Hurst CA motors and have inquired of Hurst re:help on diagnosing the mode of failure.  With such a small,outdated model as this, I can't get any service data past the initial suggestion to check for open windings, which one does have.

 

Anybody ever troubleshoot and repair these types of motors?  

 

C



#2 GJJim

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Posted 06 August 2014 - 11:15 PM

If you're talking about the synchronous AC display motors (a few watts), they are typically just replaced when they fail. I suppose you could open one up any try to repair a winding but I've never heard of anyone doing that. Some of them need a capacitor across one winding to start. Without it they will overheat and burn out.



#3 gnowellsct

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Posted 06 August 2014 - 11:34 PM

You're probably talking about the Losmandy Hursts (just a guess, but that was the outfit using hursts for about 12 years).  Even if your mopunt says celestron it's likely a Losmandy if it is sporting Hursts.

 

The Hursts were criticized (and I personally verified on my own G11) for having visible vibration at high magnification.  They were eventually replaced by the SAIA motors that you can get from Losmandy.  While I prefer to run two motors of the same make on my mount, there is no *real* need to have two Hursts.  You could throw out the bad unit and put the other one on Dec (if the good was is RA).

 

But really you don't want to go the other way around, if your RA unit is dead you don't want to put the dec unit on--get a better one, an SAIA or the new ones.

 

Because  the the SAIA motors, which are very dependable, were replaced by Losmandy with yet another brand, whose name I don't know.  You'll probably see it on their web site.  

 

So in my mind a Hurst failure is really an opportunity for a needed upgrade.  But I am curious: stepper motors are extremely tough, and don't fry easily because if they hit tight spot they cant move through or are over loaded they just stop.  That is a feature of the design.  No burn out.  So I'm wondering what went wrong.

 

Greg N



#4 gnowellsct

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Posted 06 August 2014 - 11:41 PM

Re-read your post and see you need two.  I commend you for having the ingenuity to attempt a repair.

 

While I suppose you can have gotten your Hursts anywhere, you should know that there are two highways through which Hursts are present in amateur astronomy:

 

1) As the OEM motors on older Losmandy G8s and G11s

2) As motors sold on the used market to anyone who wants them, by people upgrading their g8s/g11s to either ( a ) SAIA or other steppers or ( b ) or to the Gemini go-to system with servos

 

If Hursts you *must* have, you could probably get two cheaply by placing the following ad on astromart, in the section "mounts":

 

"Looking for inexpensive used Hurst stepper motors from the Losmandy G8 or G11.  I'm thinking some of you may have some from when you upgraded to other motors."

 

regards

Greg N



#5 GJJim

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Posted 06 August 2014 - 11:51 PM

You're probably talking about the Losmandy Hursts (just a guess, but that was the outfit using hursts for about 12 years).  Even if your mopunt says celestron it's likely a Losmandy if it is sporting Hursts.

 

 

I don't think the CA series are steppers, they are much older synchronous AC motors with gear reduction:

http://www.hurst-mot..._G_Synch_RH.pdf

 

These were common in RA drives back in the '60s.



#6 gnowellsct

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Posted 07 August 2014 - 04:24 AM

 

You're probably talking about the Losmandy Hursts (just a guess, but that was the outfit using hursts for about 12 years).  Even if your mopunt says celestron it's likely a Losmandy if it is sporting Hursts.

 

 

I don't think the CA series are steppers, they are much older synchronous AC motors with gear reduction:

http://www.hurst-mot..._G_Synch_RH.pdf

 

These were common in RA drives back in the '60s.

 

 

Oh gosh.  I was going back only *twenty* years!  You might get better results posting this query in the old telescopes section.   In this section the title will be interpreted as Losmandy steppers to the extent it is recoznized at all.  Put a little more detail in your post there...you'll probably get help.  Plus a lot of those guys actually *do* rewind motors and the like.  Greg N







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