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| Greasing isn't necessarily bad, if the excess grease is allowed to drain (some greasable motors have a drain plug below the bearing for that purpose) and if the grease is good for motor bearings and compatible with the original grease. Lots of IFs. And we usually don't know anything about the original grease. The drain should be left open until the motor has run a while, so any excess grease can run out instead of being pumped about the bearing making it run hot.
A good way to check bearings for wear is to use a dial indicator and check for sideways shaft looseness. Whether ball or bushing, when the side play (often worse in the direction of the driven pulley) gets to approaching the armature to stator clearance, its time for new bearings.
Practically, a new set of bearings has no detectable play. Detectable play with the belt off might be a hint of a need for new bearings.
More than one failed motor I've taken apart had failed, not worn out, ball bearings. They were the type with a spot welded ball cage. When the welds broke, the balls ran to the side away from the load and the motor locked up and smoked. I saw a burned SUV about ten years ago with that problem in its alternator. The belt drive overcame the rotor to stator friction, but set the alternator afire which spread under the hood.
Gerald | |
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Electric motors, how to diagnose?
