Re: E-tek motors (Re: Newbie wants grin :( )

[Lee Hart <leeahart@earthlink.net>]

"Mister Know-It-All" Lee Hart wrote:
>> These are PM motors. Do they have any brush advance? I'd guess no.

VanDerWal, Peter MSgt wrote:
> Ooh, ooh, Lee guessed wrong (that doesn't happen very often)

Hey, I said I was guessing :-)

> According to the documentation if you want maximum efficiency, and
> minimum wear, the brushes should be advanced, how much depends on the
> load/voltage. The documentation also says that if you are going to
> electrically reverse the motors having the brushes advanced is a
> 'very' bad thing.

If the documentation for the motors says so, then of course you should
do it.

> Well let's see, with 48V worth of T-105s the finished vehicle would
> weight probably 200-300 lbs more than a Citicar.

The 48v CitiCar listed its weight as 1210 lbs. Eight golf cart batteries
weigh about 500 lbs, so the CitiCar itself must be about 710 lbs. I
guess a model T is around 1000 lbs, so you're probably right; 200-300
lbs more than a CitiCar. (Notice I said "I guess" :-)

> The E-tek motor is much more powerful than the Citicar's motor

The CitiCar's series motor had a lower continuous duty horsepower (3.5hp
at 36v), but would deliver a lot more torque, and a lot more speed. This
is what allowed it to be used without a transmission.

The E-tek motor is limited to 325 amps peak, at which it produces about
30 ft.lbs of torque (another guess; had to interpolate from the curves).
The CitiCar motor produces 60 ft.lbs at 500 amps. The E-tek motor is
limited to 3600 rpm at 50v. The CitiCar used a 7.14:1 differential and
22" dia. tires, so the motor ran 4366 rpm at 40 mph.

Bottom line; a CitiCar with an E-tek motor would have a lower top speed
and worse accelleration (though range could be ~10% better due to higher
motor efficiency).

> and I believe he mentioned using the Model T tranny, though I don't
> know if that's a good idea or not since I know so little about Model
> T's.

He'd need some kind of transmission with the E-tek motor. Or two motors.
Or just use a series traction motor.

> Also, I don't know but I would guess, that those tall skinny Model T
> tires would have less rolling resistance than the Citicars short squat
> trailer wheels (however I could certainly be wrong).

Neither used low rolling resistance tires. Radials are available in
CitiCar sizes, but I don't know what you'd use for a low rolling
resistance model T tire.

> With a more efficient motor and a lower speed I would guess that it
> would get better range than a Citicar which is supposed to have a
> range of about 50 miles.

They claimed "40 to 50 miles at 27 to 32 mph", and that meant running
well broken-in T-145s totally flat on a test track. I don't think anyone
ever got 50 miles on real roads without heroic measures.

A slightly heavier model T with the same 48v batteries would probably be
worse. So, I think he would have to use more batteries.
-- 
Lee A. Hart                Ring the bells that still can ring
814 8th Ave. N.            Forget your perfect offering
Sartell, MN 56377 USA      There is a crack in everything
leeahart_at_earthlink.net  That's how the light gets in - Leonard Cohen