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Re: (ET) newbie
- Subject: Re: (ET) newbie
- From: "Paul L. Heinzerling" <PHEINZERLING compuserve com>
- Date: Wed, 2 Jun 1999 22:48:37 -0400
- Sender: owner-elec-trak cosmos5 phy tufts edu
Message text written by "Max Hall"
>if you are in the US, think used electric GOLF CARTS. They tend to have
about 3hp 36 vdc electric motors (the rough equivalent of 9 HP from a gas
engine) and can be had for less than $100 if you poke around. Also, they
have resistive (read: slightly wasteful, but cheap cheap cheap and
thoroughly adequate for your prototyping efforts -- spend money on solid
stae controllers later, or use it to get to full power w/o arcing to push
your hydrostatic drive) controllers that are tougher than boiled owls.
Good luck and keep us posted, no matter what you do. Successes and failures
are equally instructive.<
Max has a good idea here. Golf cart motors have plenty of power and the
old resistive control system is virtually bulletproof, except for an
occasional purchase of a $25 or so "solenoid" (contactor), and is eminently
understandable for those of us without electronics sophistication.
However, as with anything else, there are some things I would think you
should be careful of in a tractor application. I have a 36-volt used
electric Club Car which I have converted into a yard dump cart, tug, and
snowplow, so I can speak from at least a little experience. First of all,
these motors are not nameplate-rated for truly continuous use at full load.
(When you think about how a golf cart is intended to be used, you can see
why they don't need to be.) During a long snowplowing session this
winter, I suddenly smelled "electrical hot." I stopped the unit, and it
was over an hour before I could touch the motor without getting a burn!
Fortunately, no apparent damage, but I wouldn't want to do it too often.
Secondly, assuming my cart is sort of the industry standard, these are
series-wound motors. Among other things, what this means is that the only
thing that limits speed is the load on the motor. Consequently, if you had
an application where the motor could be turned on with no load (such as a
transaxle in neutral), the motor could speed up uncontrollably to
destruction, or, as in a phrase I read recently, spontaneously dissassemble
itself. In a golf cart, the motor is firmly geared to the differential so
that this can't happen.
Not trying to be a naysayer here, because I think it would probably work
OK. I would just suggest you take the above factors into consideration.
Also it's possible that other brands or styles of golf carts might have a
different configuration from mine.