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Re: (ET) Electric Tractor Conversion Update



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   
 
----- Original Message -----
Sent: Tuesday, November 21, 2006 8:17 AM
Subject: RE: (ET) Electric Tractor Conversion Update

Do you really think you need (2) motors.
I had always thought that the number designations that GE Elec-Trak used was suppose to be equivalent Horsepower.
i.e.; GE E15 was equivalent to a 15 HP gas tracer, GE E20 equivalent to a 20 HP gas tractor.
 
Others please comment.
 
Dennis
Elsberry, MO


From: elec-trak-bounces cosmos phy tufts edu [mailto:elec-trak-bounces cosmos phy tufts edu] On Behalf Of Mike Wallace
Sent: Tuesday, November 21, 2006 8:07 AM
To: ThompsonG DFO-MPO GC CA; elec-trak cosmos phy tufts edu
Subject: Re: (ET) Electric Tractor Conversion Update

Geof and all,
 
Speaking of converting from ICE to electric, I could use some advice and/or tips on doing something similar myself.  Ever since I met Shawn Lawless last year at the Louisville Lawn Expo and saw his ZTR, I've wanted to try something similar.
 
I recently bought an older (late 80's maybe) Model 411 Grasshopper with intentions of converting it.  It currently uses an 11 hp Briggs (horizontal shaft) driving two Eaton hydro units that then drive the wheels through 13:1 double chain reduction systems. 
 
I'm thinking about using two E15 drive motors and two Alltarx units to drive them.  Without a lot of major changes, I think I can position the two drive motors parallel to each other with one pointing east and the other pointing west.  I'll mount the smallest possible #40 sprockets to the output of each motor to drive the first 4:1 reduction.
 
One possible problem I'm wondering about is that one motor will be turning it's normal "optimum" direction and the other will be essentially running in reverse while the mower is going forward.  And visa versa for when backing up.
 
Do I need to consider modifying the brush position/location or even possibly the field winding connections such that when going the predominate forward direction, both motors are in "optimum" direction mode? 
 
With the Briggs engine gone, (this is a front mounted deck Grasshopper with the single tail caster wheel) I figure there ought to be plenty of room to finally do something with those 60+ Saft BB-600 NiCads I've had for about a year now.  
 
I figure I'll replace the current shaft driven 36" deck with a 42" ET deck and that swap shouldn't be a big deal.
 
Any of you guys got any suggestions or words of wisdom for me?
 
Mike in KY
 
----- Original Message -----
Sent: Tuesday, November 21, 2006 6:38 AM
Subject: (ET) Electric Tractor Conversion Update

Hello All

 

www.electriclawntractor.com

 

Edmonds Electric says the Electric Conversion Kids will be ready early 2007 at $2000, (not sure if that Canadian or American).. I also noticed a 36V to 120AC solid sate inverter.

 

I've got a nice little Cub Cadet just waiting for a transplant.

 

Geof Thompson

A-60,

E-81,

ER8-36,

R-36

E-8,

E-10x2,

E-12M,

E-12,

E15x2,

E-20x2,

B-145X2,

C-185,

E-141X2.

I-5

(21)

 


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