[Boatanchors] [Milsurplus] vintage motor winding question

[hwhall at compuserve.com]

Actually, here's how the laminations look on one side:
||          || 
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=================== 
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=================== 
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 ||<-rivit-> || 

On the other side they look like:
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=================== 
=========== ======= 
=================== 
=========== ======= 
=================== 
=========== ======= 
||<-rivit-> || 

If you look at that top lamination's gap, then run your eyes all around
the motor, looking at that same lam with a magnifying glass, you arrive 
back at the same gap without seeing another one. IOW, it appears each 
lamination is a single plate with only a slit in it at one point. But that 
would be nigh impossible to manufacture. They wouldn't have been able to
thread them through the winding bobbin.

Wayne
 WB4OGM

 



-----Original Message-----
From: J. Forster <jfor at quikus.com>
To: hwhall <hwhall at compuserve.com>
Cc: milsurplus <milsurplus at mailman.qth.net>; boatanchors <boatanchors at mailman.qth.net>
Sent: Wed, Sep 18, 2013 4:08 pm
Subject: Re: [Milsurplus] vintage motor winding question

OK. I would GUESS the laminations are interleaved: 
 
  ||          || 
=========== ======= 
===== ============= 
=========== ======= 
===== ============= 
=========== ======= 
===== ============= 
  ||<-rivit-> || 
 
If you remove the rivets, you can probably pull the laminations out 
one-at-a-time, unless the shading coils exclude that. 
 
Some possibilities: 
 
Strip the winding and rewind it using a circular bobbin, like a torroid 
winding machine. 
 
Strip thye winding and rewind w/ something like #22 which is easier to 
handle and will have FAR fewer turns, then put a step-down transformer in 
between the line and motor. This approach will take some calculation, but 
it's not complex. Basically you are 'converting' the motor from 115VAC to 
some lower voltage at a higher current. I's pick winding parameters so a 
6VAC filament transformer is correct, because they are common as dirt. 
 
Running it w/ reduced turns is asking for trouble, IMNSHO. 
 
-John 
 
============== 
 
 
 
 
> Yes, it is an AC motor and the frame is like you described it. 
> 
> I'd be willing to rewind from scratch if I could pull the bobbin, but the 
> stator frame is riveted together. In the frame at either end of the 
> winding bobbin, I can see gaps in each lamination, but only one per 
> lamination (I've looked all over the frame for other gaps), and they 
> alternate. I.e., the top lam shows a gap on the left side, the next lam 
> shows a gap on the right, etc. So, I cannot see how they assembled it in 
> the first place, or how I might pull the frame apart to remove the bobbin. 
> Unless the "missing gaps" are hidden under the winding bobbin. 
> 
> I've peeled 200 turns off & seem to be past the worst damage. I'm thinking 
> I might be able to use a solenoid coil like a motor "growler". If I can 
> put a mag field into the frame, a shorted turn might show by causing a 
> hacksaw blade to vibrate if touched to the frame. At least, something like 
> that is the theory for a real growler in a motor repair shop. 
> 
> We may be able to locate another motor, but they are a limited commodity 
> as you can appreciate. If we can learn to fix one, we may one day save a 
> few more. 
> 
> 73, 
> 
> Wayne 
>      WB4OGM 
> 
>  -----Original Message----- 
> 
> From: J. Forster <jfor at quikus.com> 
> To: hwhall <hwhall at compuserve.com> 
> Cc: milsurplus <milsurplus at mailman.qth.net>; boatanchors 
> <boatanchors at mailman.qth.net> 
> Sent: Wed, Sep 18, 2013 2:07 pm 
> Subject: Re: [Milsurplus] vintage motor winding question 
> 
> I assume this is an AC motor? Is the winding basically a solenoid on a "C" 
> shaped, laminated iron, core, with the motor armature in the gap of the 
> "C"? 
> 
> Actually, it doesn't matter that much what the structure is. If a winding 
> is burnt, it's finished. 
> 
> What happens is a few turns touch, the insulation fails, and you get 
> shorted turns. 
> 
> The shorted turns act like a shorted transformer secondary and heat up. 
> This promotes more failures and pretty soon the whole thing is toast. 
> 
> Aside: I've seen shorted turns causing a winding to glow dull red. 
> 
> Strip it all off and start new, IMO. 
> 
> -John 
> 
> =============== 
> 
> 
> 
> 
> >  Hope this is not too far off topic. 
> > 
> > While working on a Link Trainer restoration, the winding on a simple 
> small 
> > shaded-pole motor went up in smoke. It's 1940-ish vintage and 
> resembles 
> > the traditional record-player motor or small desk fan motor. However, 
> it 
> > is not easily replaced by a modern motor due to parts of a gear train 
> > being mounted on it. I'm peeling off turns hoping the damage is in 
> top 
> > layers and a partial rewind may repair it. 
> > 
> > My question is, when I think I've gotten past the burnt turns, and 
> have DC 
> > continuity through the winding again, is there a way to detect 
> whether 
> > there may be any shorted turns in the remaining part of the winding? 
> All I 
> > can think of right now is to see if it overheats rapidly. Is there 
> > anything else to look for? 
> > 
> > TNX & 73, 
> > 
> > Wayne 
> > WB4OGM 
> > 
> > 
> > 
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