Re: (ET) Elec-Trak Beginner Advice

["Steven Naugler" <snaugler earthlink net>]

Kevin....
    I think that you want a large frame tractor, preferably an E15 or E20.
While an E10 small frame can theoretically have the large range, the large
frame tractors have a wider deck, 42 in vs. 36 in.  There are also more
attachments for the large frame tractors.  Also, the small frame tractors 
do
not have wound field traction motors.
    Why an E15 or E20 vs. the E12, E12S, or E14?  I'll get to that in a 
bit,
but first some warning about some of the permag (permanent magnet field)
motored tractors.  The E12 has a permag traction motor known for having its
field magnets weakened.  I've been told that E14s, somewhat rare, also have
permag motors.  An E12S is an E12 with a wound field motor, better, but not
as good as an E15 or E20.  Unless you get a real deal, you want a wound
field motor.  And while you can convert a tractor with a permag motor to a
wound field motor, these E15 and E20 tractors with wound field traction
motors are just not that rare.
    Here is why you want an E15 or E20.  The E12, 12S, and 14 have only
three electrical forward speeds.  All of the large frame tractors create
motor speeds 1 and 2 by reducing the battery voltage by passing the full
armature current through large resistors.  Very wasteful.  Speed 3 has the
full battery voltage applied to the traction motor armature.  Speeds 4,5,6,
and 7, and also speed 8 only in the E20, are gotten by reducing the field
voltage while the armature still sees the full battery voltage.  (When 
field
voltage, hence field current, is reduced, motor speed increases and motor
torque decreases.)  Reducing field voltage via resistors, while wasteful, 
is
still only about 1 to 5 % as bad as the waste you get when reducing speed 
by
reducing armature voltage via resistors.
    What does this all mean.  With the 3 speed E12, 12S, and 14, your speed
selections are such that you may frequently run in the wasteful speeds 1 
and
2.  3 electrical speeds are just not enough.  With the 7 speeded E15 or the
8 speeded E20 you very seldom need speeds 1 and 2.  The E15 and E20 are 
much
easier to operate in an efficient speed, and with more speeds to choose
from, just easier to operate.
    Where to find one?  If you are near Delaware or eastern PA I might know
where to find one.  Otherwise you are better off looking locally.
    Hope this all helps.

Steve Naugler




----- Original Message -----
From: <KevinC927 aol com>
To: <elec-trak cosmos5 phy tufts edu>
Sent: Monday, April 12, 1999 10:36 PM
Subject: (ET) Elec-Trak Beginner Advice


> Hey all,
>
> I just found out about this list on Sunday and here I am.  Great idea,
thanks
> to Rhett George.
>
> I am looking to replace my old smelly, noisy John Deere 140 with 
> something
> more elegant.  The primary mission is mowing slightly cultivated weeds.  
> I
> have about 1 acre that needs attention weekly in the Spring and biweekly
up
> until November.  Any suggestions from users with similar circumstances?
>
> Also, where might I come by one of these that you suggest?  I am
moderately
> skilled with electrical devices and could do repair.
>
> Thanks,
>
> Kevin Carter
>