I’m servicing my 726 locomotive and I took apart the 671M-1 motor to clean out the dried grease from the armature shaft. When I took it apart there were 10 tiny ball bearings on the rear and only 8 on the front. How many should there be and should there be the same number in both front and back?
Thanks, Bob
Replies sorted oldest to newest
I believe the official number is 7 balls at each location. But most people put in as many as will fit. Since you have 18 balls, put in 9 on each end. They do not work together, so there is no need to coordinate the number of balls at the two ends. Use grease on the washer to hold the balls in place when you install them and use a toothpick with grease on it to install the balls. Put the balls in the upper bearing first. Then install the armature with the thrust washer already on it. Turn the motor and install the balls in the bottom bearing. With the last, forth, thrust washer and e ring installed, check the free play between the two bearings. It should be less than 0.012”. If the clearance exceeds this add another thrust washer, 0.010“ thick, at the bottom. If this clearance is not maintained, the gap can get so large that the balls can fall out.
Before the balls were reinstalled they should be cleaned. Put the clean balls on a clean flat surface and see that they will roll around freely. If they do not roll freely it may be an indication that they are no longer perfectly round. If they need replacement, change all of the balls to ensure they are all the same diameter.
My records show 9 ball bearings at each end.
Access to this requires an OGR Forum Supporting Membership
