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comments on motor rewinding   Comments on Motor Rewinding  by Tom Jarcho 

            1. Rewinding a motor is the last desparate step to take in repairing it.
             Very few Flyer motors, except for the Baldwin switcher's, need to be

             2. You can't usually tell if a motor needs rewinding by looking at it.
             Many Flyer motor windings that appear to show signs of burning actually
             work quite well.

             4. Motors need to be rewound for two reasons: because excess heat has
             damaged the insulation so that electricity passes from winding to winding
             without going thru them all, or else because the winding has been cut in a
             place that is not near the end of the coil. (see page on recovering 'near the end')

             5. Determining if a motor needs to be rewound requires some special
             equipment - an AC ammeter and a 1 volt AC power source. I don't know how
             to do it.

             6. You can get some indication of the situation sometimes using a VOM.  No
             continuity between field coil terminals or commutator poles means a broken
             winding. Often the break can be located visually or by unwinding a turn or
             two of the broken coil. If the break is near the end, the loss of a few
             windings will not have much effect. There are three possible pairings of
             the three commutator plates. If a resistance reading between any two
             plates is different than between the other two possible pairs of plates, it
             is an indication that one coil of the armature is burnt somewhat, but not
             proof. You can also compare the resistance of the armature or field in
             question with one you know is good. For instance, I have measured the
             resistance of a PA diesel pulmor field at about 2 ohms, the same armature
             at 1.6 ohms between commutator plates. A pre-pulmor steam armature should
             measure about 1.3 ohms, its field at 1.1 ohms, etc. This is not a
             totally reliable method though. Motors are rickier than that.

             7. The best way to determine if a motor needs rewinding is to fix every
             other possible thing wrong with it. The motor will thenprobably run.
             That's how I usually do it. These things will have to be repaired anyway,
             even if the motor is rewound, right?

             These include: cleaning out old lubricants, expecially from the gears;
             adding new lubricants; cleaning the commutator plates, sanding out any
             grooves in same; replacing excessively worn brushes; replacing brush
             springs; finding and fixing any reverse unit or wiring problems. In steam
             locos, the proper washers must be in place to position the armature
             correctly vs. the gear, or much additional friction is created in one
             direction. In PA and GP-7 diesels, the armature is kept in position by
             little square black hard cardboard thrust plates in the motor chassis at
             each end of the armature. If these are worn, the armature can slide too
             far forwards or backwards, causing the same extra friction. In diesels,
             the bearing straps must be completely screwed down tight or the motor will
             lose performance. The threads in the strap screw holes must not be
             stripped though. If this occurs, replace the tiny self-tapping screws with
             short 2-56 machine screws or longer screws as used on the smoke unit cover
             plates. The floating field of the diesel motor must be securely anchored
             by the 2 centering screws in the yoke.

             8. If a Flyer motor smokes and sparks huge sparks and runs very slowly, it
             may only be that there is some oil on the commutator. This can be wiped or
             sanded off.

             9. If all these annoying details are taken care of and the motor still
             runs poorly in one or both directions or not at all, THEN you might be
             looking at a rewinding job.

             10. Rewinding by hand is sloppy and results in bulkier windings. Plus,
             you have to locate and buy the proper wire sizes. You have to put the same
             number of windings of the same size wire as was on there previously, so you
             need a wire guage and a VOM too.

             11. Therefore, there are real advantages to having the work done by a
             professional. I would recommend Bob Hannon at He will
             put the proper windings on a coil with a winding machine that produces
             tighter windings. Original Flyer motors were wound on machines, not by
             hand. Check with him for prices.

             12. Flyer motors burn out for a reason. it is usually important to figure
             out why a motor burned out originally. Usually, it's because the motor had
             to work too hard. For example, the drive wheels in a steam loco could be
             out of quarter, jamming every time around. Or the valve gear could be
             damaged, providing extra resistance against the motor. In a DC loco, the
             weakening of the permanent magnet in the field may cause tha armature to
             run hott enough to become burned out. In diesels and handcars, the most
             common cause of motor burnout is that the axle holes have become worn, the
             gears don't mesh properly any more. In such a case the chassis must be
             rebushed or replaced.

             The point is this: if you don't figure out and correct the cause of the
             burnout, the new armature or field will burn out for the same reason the
             old one did! Incidentally, the motor in the Baldwin switcher does often
             burn out because the motor is so poorly designed. There are simply not
             enough windings on it and it gets too hot. This is the only Flyer motor
             like that though.

                          Tom Jarcho