|
Another 2 cents
worth.....
Series
motors provide a lot of torque at low speed but will draw a lot of amps so
resistors are used to limit the voltage which limits the current by limiting
motor speed. Shunt motors allow for torque using main field current which
can be controlled to help at low speed and reduced to provide "field weakening"
for high speed.
The
original Elec-traks used resistors for the first 3 speeds (larger frame) again
to lower the motor voltage to keep current reasonable and the field weakening
reduced field amps to allow the motor to run faster once it was up to 36
volts.
Today's DC golf cart motors have much more field capability to "force" the
fields with high amps for starting torque and taper the field for smooth speed
increase to top limited speed.
Remember that golf cart transmissions are single ratio and not rated for much
more than 750lb load so ground engagement attachments can push them to their
limit both by weight and capability along with motor heating. Higher
HP motors help this issue but golf carts are meant for higher speed runs and not
higher torque runs. Also, as noted, the frames and bodies do not lend
themselves to much load. You can really see the difference if you compare
a 4x4 (Kubota or Kawasaki or Club Car gas hauler) to a golf
cart.
Now,
the METI guys took advantage of all those designs and used a 4 speed
transmission like the old Elec-Traks to provide load rating and torque for
ground engagement attachments, added a locking differential, and used a much
larger motor and golf cart programmable drive to accomplish all the things you
need to do with a small tractor. The drive is quiet (no buzzing like older
SCR drives) and speed range smooth and it simulates driving a golf cart.
The drive is programmable and can be changed using GE Sentry software which is
standard on their drives in the golf cart industry. Since the drive has
over a 300 amp capability it is not pushed using the 100 amp motor. METI
does offer a Re-power package to upgrade older Elec-Traks to the programmable
drive and eliminate all those clicking unreliable relays using either a hand or
foot throttle and the existing motor. www.modernelectrictractors.com
...Walt From: elec-trak-bounces cosmos phy tufts edu [mailto:elec-trak-bounces cosmos phy tufts edu] On Behalf Of Paul Heinzerling Sent: Wednesday, November 12, 2008 9:15 PM To: elec-trak cosmos phy tufts edu Subject: (ET) Golf Cart for Elec-Trak Uses This is a response to several posts
back:
I've converted an old Club Car 36V
solenoid/resistor controlled golf cart for yard cart uses. I can't speak
to mowing uses, but I can talk about motor duty cycle. I've added chains
to the rear wheels, a dump bed on the back, and a heavy duty bumper from Club
Car. I put a 4+foot blade with electric lift on the front and weight in
the bed and use it for plowing my driveway. The series motor and controls
are original. It works fine, but with some caveats: I don't think
the motor is really designed for the heavy use to which I put it when
plowing. This is a lot of full-power work and in a half-hour or so will
get the motor too hot to put your hand on, and will give that warm fuzzy
"electrical hot" smell. I just let it cool off and then continue on.
Also, the gearing is more designed for travelling than working. That said,
I've used it for eleven winters and it shows no signs of
failing.
Other things to think about: Golf Cart frames
are usually aluminum and fairly chintzy. The HD bumper I put on or some
sort of reinforcement would be a necessity for any front attachment. Also,
I would think there might be problems keeping a constant ground speed when
mowing.
Regards,
Paul Heinzerling
Hudson,
OH
|