Newsgroups: comp.robotics
Path: cantaloupe.srv.cs.cmu.edu!rochester!jag
From: jag@cs.rochester.edu (Martin Jagersand)
Subject: Re: Needed: motor & controller for electric go-kart
Message-ID: <1995Mar8.175431.5449@cs.rochester.edu>
Organization: University of Rochester Computer Science Department
References: <3jiabs$ol0@alijku06.edvz.uni-linz.ac.at> <3jicpp$3i2@sundog.tiac.net>
Date: Wed, 8 Mar 1995 17:54:31 GMT
Lines: 74

In article <3jicpp$3i2@sundog.tiac.net>, Tom Cicatelli  <cica@tiac.net> wrote:
>wilbur@cast.uni-linz.ac.at (Wilhelm Burger) wrote:
>>
>> Hi,
>>     I am not sure this is the right group but I didn't find any
>> better. I want to build an electrically powered go-kart that
>> runs off regular lead batteries. Does anyone know where I could
>> get suitable motor(s) and electronics?
>> 
>> WB
>> 
>> 
>
>I'm not sure if it's the right group either, but what the heck.  Why
>don't you try going down to your local junkyard and picking up one or
>two used starter motors from an old junk car.  It would have plenty of
>torque and would run nicely on a 12 volt car battery.  
>
>I'm not sure what electronics you would use.
>
If you are short on cash I bet the used starter approach is hard to
beat pricewise. On the other hand you may end up with a one speed 
vechicle. Building a motor controller capable of handeling the
currents of a starter is not likely to be cheap.

Have you looked into buying a used gocart size electric vehicle,
and convert it for your needs? There are many different candidates:
Electric golf cart. Handicap "wheelchairs". These come in a whole range
of sophistication, from hi tech cross country versions, to standard
electric wheelchairs. Electric fork lifts and similar industrial
vehicles. From these you can probably salvage good motors,
transmissions and control electronics.

A hight tech suggestion: If you don't mind building some pretty
sophisticated electronics, buy a 3 phase asynchronous motor,
and build a frequency converter for it. For the do it yourselfer
this is actually a very cheap alternative. The only significant
items are the motor (around $100 or so) and the power FET switching
transistors ($10 - 26 each for ~10A ones, you would need 6 or more).
GTO's would be cheaper ($1) but much harder to deal with.
Siemens sells the FET's (look at for instance BUZ 66, 67 and 330's)
and has application notes for how to build a frequency converter.

I built three or four FET based frequency converters about 10 years
ago. Took about a summer including PCB design.

The advantages of this:
+ Extremely efficient motor.
+ Precise control.
+ Cheap power electronics (only if you build yourself tho)

Disadvantages:
- Standard motors tend to be 380 V (at least in Europe), by cheating a
little bit with your
waveforms you could get by with perhaps 300, but that's still a lot of
batteries. A motor running on 90-100 V would be more suitable.
(Lower than that you would start switching too big currents =>
expensive semiconductors, and higher losses)

A sports car based on this concept was built and showed on
exhibitions around Europe a few years ago. It was sponsored by
Chloride (battery manufacturer).

/m





-- 
Martin Jagersand                 email: jag@cs.rochester.edu
Computer Science Department             jag@cs.chalmers.se
University of Rochester          Fax:   (716) 461-2018
Rochester, NY 14627-0226         WWW: http://www.cs.rochester.edu/u/jag/
