Re: (ET) newbie

["Steven Naugler" <snaugler earthlink net>]

Jeff,
    Here's my two cents on your conversion.
    1.  A hydrostatic transaxle will allow you to run a single speed motor
and you'd use the transaxle to change speeds.  I think  you'd be best 
served
with a wound field or permag motor which you could run as a single speed
motor.  With the series wound you'd have the motor changing speed as your
load on the traction motor changed, so you'd have to constantly reset your
hydrostatic transmission if you wanted constant speed.
    2.  You may not be happy with the efficiency of the hydrostatic
transaxle.  A while back an experienced garden tractor guy said  to me that
when the manufacturers took a tractor with a standard transmission and
upgraded to a hydrostatic transmission, they added 2 hp to the gasoline
motor.  This was to account for losses in the hydrostatic transmission.  At
first it didn't seem right, but I looked at hydrostatic transmissions and
found them to be finned and most had small blowers for cooling.  The geared
transmissions had smooth cases and no blower.
    3.  More on efficiency:  When Wheel Horse, who bought the GE design and
stock, designed their E181 electric tractor they used a constant speed
electric traction motor and a multi speed shift on the fly transaxle.  My
suspicion is that hydrostatic was too expensive both in terms of losses and
purchase cost.
    4.  Except for light use the 3 hp golf cart motor will probably be too
light.  Light use would be mowing so long as the mower deck had its own
motor set.  Even the GE E15 and E20, which had 1.5 kW and 1.8 kW constant
duty traction motors used separate motors for accessories.  If you simply
replaced the gas motor with an electric you'd have to size it for
simultaneously powering the traction and accessory loads.
    Now that is sounds like I'm trying to talk you out of this conversion,
I'll say you'd be partially right.  I believe that the golf cart motor will
not serve you well, and if you did use it, you'll still need separate 
motors
for the mower deck.  And I'd advise you to not plow or do other heavy
traction jobs with it.  It's 3 hp is not a constant duty 3 hp.
    I think that applying the hydrostatic transaxle to a GE tractor with a
fixed speed motor, such as an E8 or E10, or even an E12,15, or 20 with bad
controls might be neat.  One of my dislikes of the standard E15 I use is 
the
inability to shift transmission gears on the fly; you have to stop the
motor, shift, then restart.  This includes reversing.  And while a modern
electronic controller would allow better motor speed control, we are still
limited to whatever speed and torque range the currently selected gear
allows.
    I have a GE ER8-36, an electric riding lawnmower, minus the traction
motor and 5 speed shift on the fly transmission.  I was thinking of using 
an
E15 motor, oversized for the job, and using a hydrostatic transmission.  So
long as the batteries have excess capacity for the actual lawn I mow, I'd
accept the losses in the hydrostatic transmission.  The only problem is
finding a good used cheap hydrostatic transmission and E15 motor.
    So good luck with however you do your conversion.

Steve Naugler

----- Original Message -----
From: Jeff Tickner <jefft softlanding com>
To: <elec-trak cosmos5 phy tufts edu>
Sent: Wednesday, June 02, 1999 4:50 PM
Subject: (ET) newbie


> I have a Craftsman lawn tractor I want to convert to electric. It has a
> hydrostatic transaxle so do I need a controller? Any sources for
> inexpensive DC motors, maybe used? It was a 15HP, used with a mowing deck
> and snowblower, what size motor is reccomended?
> Thanks!!
>
>