The snow plow that I use to clear the driveway here stopped working. The winch which raises the blade stopped running, and since it seemed to be related to the cold weather (and heating the unit appeared to fix it temporarily) I figured there must be ice in the gearbox or motor housing. Opening up the gear box revealed nothing suspect, but even with the gears removed I had trouble turning the output shaft of the motor.
I reassembled the gearbox, then took the motor casing apart. This is a permanent magnet motor, and at least one of the magnets had come loose and was clinging to the armature. Every time the motor turned some of the face of this magnet would get ground off. The banging around each time the motor reversed also chipped and cracked the other magnets, so the motor was filled with black dust and crumbs in a whole range of sizes. The real problem, though, was that this was magnetic dust (and probably a good abrasive), and I was using the same workbench area I was using to refurbish a Monotype mould. I was certainly not expecting this sort of mess to come out of this motor.
You can see a crossblock and other mould parts near the back edge of the paper table cover, and some of the magnets coated with a fur of dust just in front of the motor casing.
I spent part of this evening carefully picking up each tool, wiping off most of the dust, using adhesive tape to pull off the rest, and putting the cleaned tool aside. I did the same for the mould parts. I bagged all the parts of the motor in Ziploc bags and put them aside. The paper table cover was carefully folded over with all the dirty towels and tape inside and tossed in the trash. I wiped down the tabletop a couple of times and replaced the paper table cover.
Now, with a clean work area, I went over the mould parts again for any remnants of the dust. The motor can perhaps be repaired by gluing the magnets back in, but that is a summer job, when I can work outside and not have to worry about the dust. For now I am replacing the entire winch on the plow.