Motor problems

["Rhett T. George" <rtg ee duke edu>]

 - Greetings -

Happy New Year.

Christopher and David have discussed a recalcitrant motor that
comes up with an occasional dead spot.  In such an event, pre-
suming that the Elec-Trak has an ammeter (or load meter), just
watch the meter when the motor is energized.  If no current is
drawn, one brush is likely not touching.  If much current is 
drawn, then a bearing is likely stuck.  Since the armature must
turn in the bearings, it would be uncommon that one could turn
the shaft by hand.  Therefore the probable problem is worn
brushes.  If the brushes are down this far that one occasionally
will not touch, arcing will increase and the commutator will be
pitted - not good!

In smaller motors I have replaced brushes in incidents of the 
commutator having been pitted.  Running with no load for perhaps
a half hour cleaned up the commutator with no ill effects except
the loss of a bit of brush life.

Hope this helps.

                                        Rhett George

PS
  In neutral, the motor and transmission input shafts seem to coast
five to ten revolutions from low speed to off - this on the E 15 
and the E 20.
                                        R G