Re: [CAD_CAM_EDM_DRO] Automobile starter motor as servo??

R Rogers wrote:

>
>
>
>
>
>All this discussion about practically any DC motor as a servo. I'm wondering how well a starter motor would work off of a car. They are about NEMA 42 sized. The voltage is low and the amperage is high. But, maybe run one off of higher than usual voltage as they were saying yesterday was ok to do. Like 40 volts and 15 amps. I think it would work. Sure cheap enough, the junkyard is full of them. very rugged too. Spare brushes would be no problem. When I pulled my servos apart to remove the electronic brakes, they looked exactly like starter motors inside
>
>

If you can get one with permanent magnets, it might work. But, it is
wound for something like 6000 RPM
at 12 V. So, you would end up needing a 50 A 12 V servo drive. A Gecko
drive would barely be able to
turn it with no load. Second, they usually don't have a lot of
commutator segments, as the torque ripple
is not a big concern for cranking a gas engine. If it is the typical,
old-style series wound field motor, you
would have to rewind the series field for some reasonable voltage, since
these fields are something
like 1/4 V 100 A. Most starters have sleeve bearings, as they are used
to spinning fast, and have an
expected life of a couple of hours of actual running. Finally, they
ALWAYS have one brush grounded,
and you'd have to break the connection.

Jon