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Reply to "Permanent Magnet Open Frame Motor"

Short answer is YES it could be done.  And you could indeed control motor direction by reversing polarity to the brushes.  However the 3-pole armature would still produce big changes in back-EMF as it rotates, which would likely frustrate attempts at closed-loop speed control.  TrainAmerica experimented a LOT with this, and the 3-pole armature was a deal-breaker.

Marklin locos are built a lot like postwar Lionel.  In the late '90s Marklin offered an upgrade kit for their vintage AC motored, spur-geared locomotives.  It actually replaced the wound field assembly with a new one containing a rare earth magnet.  More importantly, the kit included a FIVE-POLE armature to complement the new field.  (Google "Marklin Five-star high efficiency propulsion" for details.)  I would love it if Lionel offered something like this to upgrade a postwar 2046, for example.  But I've been waiting 20 yrs, and unless Neil Young makes it a personal project and gift to the faithful, it probably won't happen. 

Another approach is to replace the field AND armature with a "pancake"-style can motor.  See this thread for an example:  https://ogrforum.ogaugerr.com/...-gear-2036-127-pitch

There are also a couple of threads on the forum about replacing Berkshire or Hudson-style longitudinal Pullmor motors with a cylindrical can motor.  Frank Timko offers a service like this.  But the can motor has to be pretty small to match the form factor of the Pullmor's offset field winding.  And IMO a tiny can motor isn't well-suited to the tall gearing of a postwar loco.  Good question, worth discussing!

Last edited by Ted S

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