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
rewound.
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 Hannon@erols.com. 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
