736 / 2023 Motor Thrust Bearings

A small amount of play is normal. If you reverse directions while the engine is on the work bench you can notice the brushes rising up or down in their wells. There are some who think that an extra washer or two should be used to keep the armature from pushing up against the brushes. That would require adding the extra washers to the lower stack. Your new performance results may vary.

Luther:  Lionel specs. that a  .010ths play is allowed in the armature vertical movement, which would be one (1) of the  671M-23 thrust washers.  Your washers are probably a bit worn, so there is a bit more vertical "thrust" allowance than if you placed all new thrust washers  during your motor cleaning/overhaul.

          While the 2023 motor is okay as is, the more critical motor, the 736 needs to be secured into the loco chassis frame and a proper motor worm to axle gear mesh, when reassembled. I personally would take the excess play out of the 736 motor, so the armature does not thrust up or down/forward or back too much when cycling the 736's reverse unit and changing direction of the loco, but that is my personal preference. The gear to worm mesh is the more important.

          Old Lionel Corp. use to use different thickness of shim washers under the motor casting where there are two pins coming up from the frame to align the motor just in front of the mounting screws; however, these are hard to find now (colored blue or white).  In more modern times, an adjustable set-screw has been used from under the frame casting, up thru the frame, against the motor casting to pitch it up a bit higher to adjust the mesh against the gear.  If your unit is older and does not have the screw hole or a set-screw, then brass shim stock could be used to adjust the pitch of the motor in place of the thrust washers, and hence the mesh of the worm to the gear.  Let us know what you end up doing and how it works.  Dennis M.

I've tried to find those motor shim washers that Dennis M wrote about. So far no luck. When I've needed them, I made them from shim stock, as he wrote.

IMHO, when you are adding a washer, and making it spin more stiffly you are creating a binding condition. If the engines were on my bench, I would not add the extra washer. A little end play is normal, and should not affect gear mesh.

So how do you measure the worm to axle gear mesh?  How do you determine the correct pitch of the motor?  G

C W Burfle:  I'm with you in not wanting to  "Bind" the motor up, but I do like to remove as much excess backlash/thrusting that the armature will do to get a smoother running drive train. In some cases, I've used both new and older/used thrust washers to adjust the armature movement; even changing out the ball bearing cage to remove the play.  So yes, do not bind the motor, but be sure you don't have too much backlash in the armature.

          So how do you gauge the worm to axle gear mesh?  Well you obviously can't do it like you would with an automotive rear end  and blue gear tooth dye. also, the space is too confining for feeler gauges.  I guess it comes down to a bit of "trial and error" along with experience.

          If you tighten down the motor mounting screws and the motor has a hard time turning and clearing the gear teeth, then it is safe to say that the motor could use shimming. Start with a few thousandths spacer and try it again.  I find that a good messed motor to gear, will allow the chassis to roll freely when pushed along a flat surface. Now, that's to say that no other problem exists with the side rod holes, or the wheel quartering or even the axle shaft bushings. The more miles on them and the more likely to have wear that will effect how good the unit will run with only a few parts replaced.

          You also asked about where to add the washers if needed, top or bottom of the casting.  I always look to match up the armature pole segments/laminations (where the wire is wound on the armature) so that it is in line with the field laminations of the casting.                                                                                                While this motor is an AC/DC Universal motor, it also has been called other names too (some not too nice by those who dislike the pullmore motor). Among them are: the AC/DC Universal Motor, A repulsion motor, and even a magnetic bearing motor.                                               The repulsion factor is when the armature rotates around and the brushes energize and de-energize the armature poles. one pole becomes de-energized and gets "kicked around"/repulsed until another segment/pole is energized and another is de-energized. So rather than pulling the motor around, it is "Pushed"/repulsed around.                                                                                                                          The magnetic bearing motor term is nice in that it acts much as a plasma containment unit does in using magnets to fix a plasma core in a contained magnetic field (how's that for bringing the lowly pullmore motor into the 21st century!) The motor is electrically connected in series and as the field laminations on the casting are energized with the field building up as more power is applied, the armature of the motor will begin to rise up to match it's pole laminations with the ones of the field.                                                                                                                     In days of old, Lionel Corp. would have used spacer washers at the top of the armature to restrict the upward movement of the armature and they would have pressed against the oilite bushing in the brushplate.  Newer Lionel, in some instances, did away with the brushplate bushing. To control the upward thrust of the armature, either the thrust washers were used at the casting level, or as has been seen, a set-screw was used in a tower at the top of the motor armature brushplate that could be set to the allowable thrust spec.                                                                         The magnetic field also acts as a dynamic brake to keep the motor from "running away from its self"  The stronger the motor field gets, harder it is for the armature to spin itself into oblivion.

                       Okay, too much info, but you get the picture:  plasma containment/Pullmore motor.   Dennis M.