I recently purchased a Marx whistling station. It didn't work and in the process of cleaning and lubing the motor I discovered that the motor was a 4-pole motor. All of the small motors that I have worked on in the past have had a 3, 5, or 7 pole motor. I thought that small series motors had an odd number of poles. Has anyone seen a 4-pole motor used in a train product?
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Has nothing to do with series wiring. Has everything to do with self starting.
If your field has 2 poles and your armature had 2 poles, It could stop where it might not start- especially under load because there are weak spots in the rotation. I found as a kid some battery operated toys had no power switches and used 2 pole motors where you flick or spin something to start the motor. In fact, this kit has just such a motor "Atlantis Peanuts Snoopy and Sopwith Camel Aircraft Snap Model Kit"
3 was a number often used to ENSURE easy self starting of the motor with a 2 pole stator (same rule applies to permanent magnet based motors.
So yes, 3,5,7 armature segments are common counts with a 2 pole stator.
I'm thinking they "get away with it" since it's an air whistle and fan with low starting torque.
If you put that same 4 pole motor under a starting load with mass or friction (example main drive motor function) it might not start from a random dead stop reliably.
Attachments
Just Marx stations like this.
So one theory I have is a 4 pole motor was chosen because of the high cogging could change the sound and interpose a "beat" pitch on top of the air whistle frequency giving a unique sound. Again, the 4 pole motor would be extremely "coggy" with high torsional vibration and given a light plastic air impeller, the low starting torque was not an issue. Further, this particular normally odd arrangement might control the RPM better (example max RPM) as the input voltage varies giving the whistle a specific sound even as voltage varies.
Also, found and clipped this video segment of the pole arrangement and self starting of 2 VS 3 poles).
@Vernon Barry posted:
Semi OT: This was a fave of mine as a lad. Nice to see them back in production!
https://atlantis-models.com/sn...mel-with-motor-snap/
https://atlantis-models.com/re...ane-with-motor-snap/
Mitch
It is strange. Notice in Rob's pic, the brush tubes are 90 degree offset, not the normal 180.
Very cool find David! For years I've hoped that someone would come up with a 5-pole armature and brush plate that could be used to improve the operation of postwar Lionel. This is the first time that I've seen any of these motors with more than 3 poles. Still hoping!!