Might have been a year ago I hit something with the lawnmower and broke the mower. I know exactly what I hit. It’s a big honkin’ hunk of cast iron, the thing the gas company could turn to cut off the gas supply to the house from the street. It’s been there all along, and I try to remember it so as not to damage the mower or the valve, but every once in a while I forget. Once years ago I hit it and broke the lawnmower blade. Last summer when I hit it the lawnmower came to a sudden stop and started smelling of burning insulation (it’s an electric lawnmower, not a gasoline one.) The motor wouldn’t move at all. When I was convinced it wasn’t going to change its mind, I rolled it back to the garage and thought I’d see if I could take it apart and figure out what was wrong before buying a new one.<\/p>\n
Well, around the middle of May, one night when Arlene had book club and I didn’t have klezmer, I finally did start taking it apart. When I got to the point where the motor was exposed, I found that I could turn the motor around, but it seemed to stick sometimes.<\/p>\n
When I was a kid I had a little kit to build a toy electric motor. It was surprisingly simple. The idea is to arrange little coils of wire in such a way that electricity gets switched on and off to turn the coils into electromagnets that pull themselves a little way, then get switched off while the next coil gets turned on and pulls itself a little way. The lawnmower motor was equally simple. There was a big cylinder, or really a thin metal can holding two halves of a big cylinder split in half lengthwise, with a rotor in the middle which was the set of electromagnets. I tried to pull the rotor out, but it felt as if there was a heavy spring holding it in place. I looked at both ends of the rotor but couldn’t see any spring on either end. It was a puzzle.
\nTwo days later Arlene asked if there would be anything helpful on line. I found an appliance parts site that had an exploded drawing of the whole lawnmower (so people can figure out what spare part to order) that was indeed helpful. It didn’t show any spring, so I tried again to take the rotor out. It still didn’t come all the way out, but it did move far enough that I was able to spot a big chunk of something broken in between the two halves of the split cylinder. That was obviously enough to keep the rotor from moving, and obviously shouldn’t have been there, so I took it out. It turned out to be magnetic stuff. The half-cylinders were big permanent magnets that the motor’s temporary electromagnets pull themselves to, and this chunk had apparently broken off when the impact knocked the rotor against the cylinder.<\/p>\n
I put the motor back together without the blade, plugged it in and turned the switch, and the motor hummed. I unplugged it, put the blade on and put the rest of the mower back together, and tried to cut the grass. It ran like a champ.<\/p>\n
I didn’t figure out until the next morning that there was no spring holding the rotor in. It was all that big magnetic cylinder doing the work. I was pulling against a big magnet.<\/p>\n","protected":false},"excerpt":{"rendered":"
Might have been a year ago I hit something with the lawnmower and broke the mower. I know exactly what I hit. It’s a big honkin’ hunk of cast iron, the thing the gas company could turn to cut off the gas supply to the house from the street. It’s been there all along, and … <\/p>\n