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dang PM lawn mower motor

Somehow I seem to think that a universal motor with a wound field will also brake if you short its power input terminals, but prolly not as much as a PM one will.

But maybe I'm wrong about that, I don't seem to recall ever being warned not to touch a vacuum cleaner's line cord plug prongs while the motor is still spinning if you pull the plug out of the wall while its running.

It's time for an experiment when I get home tonite. All it needs is my old GE canister vacuum, my Simpson 260 meter and an extension cord to make it easy to put the meter across the vacuum's line cord plug.

More later,

Jeff

Reply to
Jeff Wisnia
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Wave spring is a name used also. Smalley is the name you're thinking of...

Reply to
syoung

FWIW, I have a couple of weed-wacker motors that utilized a diode in one of the power leads for running the PM motor on 120VAC. I haven't measured the speed with a tach, but they wind up to a fairly high speed. The trimmer label claimed they are 3/4 HP.

The motors are about 4" diameter and maybe 5" long (not including the shaft), and have a 3/8-24 RH thread for affixing the trimmer line spool. So, removing and remounting the motors made them useful for other uses. This is a handy thread for attaching a chuck or other gizmos to.

The bearings are bush type oilite material, but the motor end bells have enough material to support ball bearings, if they were machined out to accept them.

WB ...........

Jeff Wisnia wrote:

Reply to
Wild Bill

Well I sure get a big fat "F" for that theory. There wasn't much electrical coming back out of the switched on vacuum cleaner's disconnected power cord once it was yanked out of the receptical it was plugged into.

I even went so far as to hook a scope (set for DC measurements) across the cord and there sure wasn't any significant DC there while the motor was coasting down to a stop. Just a couple of hundred millivolts of AC "hum" prolly coming from the fact that I was lazy and left the scope input stay refrenced to ground, not the neutral line.

I guess there just isn't significant retained magnetism in the stators of those kinds of motors, huh?

I must have been relating universal motors to the 6 volt generators on my first few cars. Now that I think about that I remember that once in a while, when replacing a generator, you'd have to "polarize" it to match the car's battery ground polarity by "gausing up" the field with a quick jump from the hot side of the battery to the genny's field terminal.

Thanks for the mammaries,

Jeff

Reply to
Jeff Wisnia

Yep. I rescued an old Dayton 3.5kw genset from a 1960's era bomb shelter. It didn't take much to get that old 8HP updraft Briggs running, but nada from the generator until we "rang" it, so it would self-excite.

LLoyd

Reply to
Lloyd E. Sponenburgh

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