Skip to main content

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?

Marx 4 pole Motor

Attachments

Images (1)
  • Marx 4 pole Motor
Original Post

Replies sorted oldest to newest

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"

Screen Shot 2023-05-24 at 8.06.11 AM

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

Images (1)
  • Screen Shot 2023-05-24 at 8.06.11 AM
Last edited by Vernon Barry

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).

https://youtube.com/clip/UgkxE...jFkpSN2dzKnHgptoRKsS

Last edited by Vernon Barry

Add Reply

Post

OGR Publishing, Inc., 1310 Eastside Centre Ct, Suite 6, Mountain Home, AR 72653
800-980-OGRR (6477)
www.ogaugerr.com

×
×
×
×
Link copied to your clipboard.
×
×