jerry freedomev via EV wrote:
Hi Dan and All,
> Looked at EVDRive and interesting but I was trying to find a lower
> cost solution...
I think we can help you there. Controlling a Sepex motor is almost as
easy as a series motor. :-)
As for 6.7" lasting I've been abusing them for decades now and they
> take it well normally running at 2 x rated power even in Florida heat
> with a fan.
I agree. My ComutaVan, and my LeCar both had 6.7" motors. I never had a
bit of trouble with them failing or overheating. Of course, I live in
Minnesota. But you can easily add an external blower for cooling.
You might also try Bob Rice's solution. He used *two* golf cart motors,
one per wheel. He switched them in series/parallel, to effectively have
a 2-speed transmission. It also eliminated the differential.
I'm planning a very low drag EV, 60-80wthr/mile so even at 50mph if
> the gearing lets it should be a problem.
You can also tweak the ratio with tire size, as you said.
First hitting the power supply/field full on and then the start
> solenoid with resistor inline, then short out the resistor and then
> reduce the field to increase speed?
Yes, that's what I did for my very first EV. It was a 1974 Datsun
pickup, with 72v of golf cart batteries in the bed, and a surplus 30v
500a aircraft generator for a motor. This is in effect a sepex motor.
My homemade controller used a big rheostat to control the field current.
It was connected to the accelerator pedal. The armature was powered by a
contactor controller, which could apply 36v or 72, with or without a
series starting resistor.
It's important to wire it so you can't apply power to the armature
unless there is field current. In my case, I had a relay coil in series
with the field that had to be pulled in to enable power for the armature
controller's contactors. If I dig around a bit, I can probably find my
old controller schematic.
It was a very drive-able setup. Good speed control, smooth
accelleration, and very strong regenerative braking. However, it was
quite unlike any normal car's throttle response. The accellerator pedal
behaved more like a cruise control; moving it caused the motor to try
very hard to move to the new speed. In particular, removing your foot
from the accellerator pedal commanded *full regen*, which would lock the
tires on anything but dry pavement.
Whether we or our politicians know it or not, Nature is party to all
our deals and decisions, and she has more votes, a longer memory,
and a sterner sense of justice than we do. -- Wendell Berry
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)