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

ditto, my experience in the starter/alternator biz says the armature will
probably overheat. made for a few seconds to start and engine. also armature
speeds can exceed 25,000 rpm in reduction style Japanese starters, the
current draw is very high for a servo amp to handle. cul brian f.

----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, January 31, 2005 12:49 AM
Subject: 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
>
>
>
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