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The instent I'd
suspect was that the GE designers were trying to compare ICE tractors to the
electric ones having similar capabilities....
Torque is what is
needed to move things....DC motors have rated torque at low speed where ICE
engines do not.
The grasshopper
conversion is interesting.....remember, increasing the ratio multiplies torque,
reducing it divides it. You may find the DC motor won't be able to handle
it through that much gear reduction. That's the reason for the Peerless
transmission in the ET's (plus the benefit of one drive motor like an
ICE). But, you are using 2 motors
now.
The compound
winding in the drive motor is needed for the dominant direction.
DC motors use the
shunt/main fields to produce flux and when armature current runs
perpendicular to it, torque is produced (T = Ia x Flux x constant). When
motor size (amps) is increased, the amps in the armature actually start to
decrease the field flux at higher loads and weaker flux means less torque and
higher speed/more amps. If you don't reverse the "series" (or stabilizing
compound field), the motor will really start to increase speed with load
(because you are "negating" the field flux and not adding to it) and commutate
poorly. If there isn't an external jumper to change it, the motor can be
taken apart and changed per the connection diagram.
Keep us posted if
you do it......I was thinking of making a 4WD Elec-Trak someday....saw a photo a
while back where someone took two rear ends and put them together with
articulated steering but never heard if it worked.
....Walt
Erie
PA
-----Original Message-----
From: elec-trak-bounces cosmos phy tufts edu [mailto:elec-trak-bounces cosmos phy tufts edu]On Behalf Of Mike Wallace Sent: Thursday, November 23, 2006 2:56 AM To: Pestka, Dennis J; ThompsonG DFO-MPO GC CA; elec-trak cosmos phy tufts edu Subject: Re: (ET) Electric Tractor Conversion Update Dennis,
Yes I'd need two motors, if I replace the
current ICE and the two hydro units with electric motors.
As for the "number designations
that GE Elec-Trak used was suppose to be equivalent Horsepower", that's kinda correct, but...
What GE really probably meant was that they were equivalent
with respect to torque, not horse power.
Based on
performance curves and engineering data that I acquired from Len Knecht who
worked for the General Purpose Motor Department at GE's motor facility in
Fort Wayne , Indiana back in 1979; an E15 motor was rated by GE at 1 HP @ 2250
RPM, the E20 motor was rated at 1.2 HP at 2250 RPM, and the series wound
snow blower motor was rated at 2 1/2 HP at 3100
RPM.
Mike in
KY
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