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Saving a older style electic motor

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  • Member since
    October, 2006
  • From: York Maine
  • 115 posts
Saving a older style electic motor
Posted by MrMick on Sunday, July 30, 2017 9:34 AM

I have an old steam locomotive ( how old? cast body (non-magnetic, possibly 'white metal"), chassis has only "New One Model Tokyo Japan" on the bottom.  It stopped running so i sdisassembled it and removed the motor. It has an open frame ( can see the rotor), and what looks like the stator are formed steel pieces which have a permant magnet at the back end, held by the stator pieces between  them.  The motor  worm gear turns the chassis spur gear.  I have lubricated the brushes (LaBelle 108 oil) and in  my hand the motor spins pretty well - this issue is that it won't start to spin by itself - IF I turn the shaft, while energized, it spins on its own and responds correctly to changes in the DC current; once it stops it won't restart by itself, (although at one time it obviously did). I would like to keep the loco but only if it can move on it's own. Any thoughts on what I can do to get it to start spinning on its own? Max Voltage applied is abt 18 Vdc. The rotor  has 5 segments. the brushes spark when it is running. I know it may be time to bite the bullet, but I'm hoping that something can be tried....more LaBelle?

 

Update: Upon close examination it appears that there is a little slop - rotation-wise- between the  commutator  and the rotor; i.e., if I press on the commutator I can rotate the shaft/rotor a smidgen. probably not designed that way?

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Posted by 7j43k on Sunday, July 30, 2017 10:11 AM

One doesn't lubricate motor brushes with oil.  They are meant to run dry.

I suspect that the oil is now a part of your problem.  And I suspect you will have to remove the oil as a solution.

 

Ed

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  • From: Canada, eh?
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Posted by doctorwayne on Sunday, July 30, 2017 10:20 AM

Most open frame motors have felt pads at each end of the motor which act as reservoirs for lubricant, and that's about the only place I would add oil.  If it's an older motor, the pads may have dried out and will accept a surprising amount of oil. 
The brushes and commutator need to be cleaned of oil, though and you can also use the back of an X-Acto blade to carefully clean the crud from between the segments of the commutator. 
In the past, carbon tetrachloride would have been used for oil removal, but alcohol is likely preferable nowadays.  You can also polish the commutator using very fine (1600 or finer) wet/dry sandpaper - use it dry.
A useful upgrade for open frame motors is to replace the magnets with rare earth magnets.  The procedure is to stack as many as will fit in the space where the original magnets were, then make-up any remaining gap with steel plate - a cut-up sheet steel weight from a freight car works well.  Even though the stack of new magnets is of less area than the originals, you will be amazed at the improvement in performance.  This includes lower current draw, lower starting voltage, lower top speed, and more pulling power (relative to weight, of course).
Micro Mark offers such magnets, but there are lots of other sources, too.

Wayne

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Posted by RR_Mel on Sunday, July 30, 2017 11:00 AM

Wouldn’t hurt to post a picture of your motor.  Back in their day most open frame model railroad motors were made by Pittman.  Pittman sold their dies to Bowser many years ago, Bowser has a fairly good stock of parts for the Pittman motors.
 
All of the above info is good to try, as stated above the commutator and brushes must be clean and dry from any oil.  Do oil the bearings, if the felt pads are dry fresh oil will make a huge difference.
 
Another thing to check is the brush tension to the commutator.  Weak spring tension or dirt in the spring pockets will cause low current transfer.  The motor at start needs good current transfer.  Slight arching at the communtator brush is normal.
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
  • Member since
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  • From: York Maine
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Posted by MrMick on Sunday, July 30, 2017 12:05 PM

Labelle 108 states it is fine for brushes.; I also think LaBElle 107 can be used for brushes, too. I updated the OP to reflect a little rotational slop beween the commutator and the rotor. I will check out the Bowser site to see what i can find out about the availabliity of a replacement 'pittman' motor. I will also try to append a photo.  NOte that the 'non-starting" aspect existed before I applied the oil- which did not seem to have any effect. I will clean out the slots in the commutator, also. I appreciate the suggestions.

  • Member since
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  • From: Bedford, MA, USA
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Posted by MisterBeasley on Monday, July 31, 2017 10:29 AM

I would also replace the motor.  The old ones use a surprising amount of power vs. new ones, and even if you get it running now, it will be a maintenance headache forever.

When I started back in the hobby a dozen or so years ago, I unpacked boxes from my teenage years that I'd packed 40 years ago.  I cleaned and oiled the old engines, but found they ran very poorly.  Then I looked a new models, and realized that the old ones could be dummies or siding models.  I still run my old rolling stock, now upgraded to metal wheels and Kadee couplers, but the old engines are just dummies now.

It takes an iron man to play with a toy iron horse. 

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Posted by 7j43k on Monday, July 31, 2017 11:41 AM

MrMick
 

Update: Upon close examination it appears that there is a little slop - rotation-wise- between the  commutator  and the rotor; i.e., if I press on the commutator I can rotate the shaft/rotor a smidgen. probably not designed that way?

 

I am sure the designers did not intend for the commutator to rotate on the shaft.  But it it's slight, it would not be likely to cause the motor to not be able to start itself.

One note, by the way.  If one or more of the wires gets disconnected from the commutator, the motor won't start when the appropriate segment lands under a brush.  This non-start will only happen occasionally, though.  As in:  not always.  Once started, however, the motor will run.  This MAY describe your situation.

Also of interest is brush wear.  As brushes wear, brush spring tension will decrease.  Until, of course, they are fully worn out.  When they get to the fully-worn-out point, they can damage the commutator.  As they approach this point, motor operation gets "funny".  I have only run into this once (maybe I don't run my trains enough).  It was with a Sherline milling machine.  I changed the brushes and got back to work.

 

I recommend examining the brushes for wear.  Having a fresh pair for comparison is quite useful.  You likely don't.  An alternative would be photographs of the same motor.  You can get a sense of the "fresh" size.  There are photographs of most Pittman motors.

I would also recommend removing the brushes and soaking them in an appropriate solvent until the oil is removed.  While it appears to do no harm, neither does it appear to do anything good.

You can now more easily examine the commutator.  If it looks "ugly" you can likely clean it up (as noted by others).  I put quotes on "ugly" because most of our motors have a wee bit of it and appear to be fine.  I am suggesting "excessive ugliness", which words suggest subjectivity.

 

Oh, yes.  I would also suggest removing the oil from the commutator.  The slop in its attachment could possibly be removed by applying ACC to the point where it meets the shaft, though I suspect the oil will have to be removed first.  Another attachment possibility is at the point where the commutator elements end and the coil windings start.  In this case, I would recommend epoxy.  And an oil-less base.

 

 

Ed

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Posted by RR_Mel on Monday, July 31, 2017 1:03 PM

I have a pair of last run Pittman DC-71 motors that I bought for a project back in the late 1980s that never saw completion. This is what the Pittman motors look like.  Both have the isolated brush holders for DCC operation.
 
  
 
Here is a link to Bowser motor parts:
 
 
One of the things mentioned in the above posts is the magnet flux, very old Analco magnets can loose flux density over long periods of time and that could reduce the power of the motor immensely.  As mentioned above replacing the magnet with a newer rare Earth magnet would increase the power by as much a 4X over the Analco magnet.   
 
Good luck!
 
 
Mel
 
Modeling the early to mid 1950s SP in HO scale since 1951
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
 
  • Member since
    October, 2006
  • From: Western, MA
  • 7,298 posts
Posted by richg1998 on Monday, July 31, 2017 2:05 PM

 

As an extra, the worm is on the motor. It drives the worm gear on the driver axle. That gear looks almost like a spur gear but the threads cut at an angle to match the worm.

Right out of a NWSL tutorial.

 

Rich

 

N

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Posted by Redvdub1 on Tuesday, August 01, 2017 3:12 PM

ditto to the other suggestions.  You did not say you inpsected the brushes..if they are completely worn down you have to replace them...sounds like you could see them so they might be "ok".  Hardened grease/oil is another possibility.  I suggest removing the rotor assembly..don't worry about losing magnetic field strength.  Clean the shafts thoroughly and the front/rear bushings.  Reassemble/spin rotor/"feel" for "hitches".  Check for continuity between the commutator segments.  The rotor assembly must spin as "loose as a goose".  Any "drag" is no good.  You may need to polish the rotor shafts and ream the bushings to get the"loose as a goose" result.  And if your motor shafts are mounted through "pillow blocks" fore and aft I would guess the pillow blocks bushing surfaces could well be the problem.  I have had problems with those things on my old engines.

Good luck. 

Super magnets will help only if everything else is aok. 

 

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  • From: Bradford, Ontario
  • 7,357 posts
Posted by hon30critter on Wednesday, August 02, 2017 12:36 AM

7j43k
If one or more of the wires gets disconnected from the commutator, the motor won't start when the appropriate segment lands under a brush.

I'll put my vote with Ed. I suspect that you have a broken commutator wire. The suggested lubrication problems wouldn't cause the motor to be 'dead' on start up. It may not spin, but it should at least hum. If you are not getting any movement or any noise then there is likely an electrical fault. The loose commutator could well have caused a wire to break.

I wouldn't waste my time trying to fix it. It would be extremely difficult to re-establish the connection, and then it probably wouldn't last. Go to Bowser as suggested, or have a look on eBay.

By the way, replacing the old magnet with neodymium magnets works miracles!

Good luck with it,

Dave

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