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Re: (ET) ICE to electric conversion
Excellent feedback (below) from Darryl! If
I may, I'd just like to add a few more cents worth:
Universal Motors: I'd
avoid universal motors. Universal motors are truly nothing more than a
series-wound DC motor with laminated cores (to deal with AC eddy currents) and a
few fewer turns in the windings (to deal with AC inductive
reactance. Therefore, being nearly the same as a series-wound motor,
its internal speed regulation (how well it holds constant speed under changing
load conditions) really stinks.
"Forward" Rotation:
Standard forward rotation for electric motors is clockwise, when looking from
the load toward the motor's shaft, or (of course) counter-clockwise when looking
from the tail end of the motor toward the load. Reverse rotation is
easily doen by swapping the polarity of either the armature current or the field
current...BUT...brush orientation and interpoles (compensating windings) may
make running in reverse (for extended periods of time) infeasible.
Interpoles are sometimes built into DC motors to offset armature reaction in a
variable load situation...but they tend to work much better in one direction
than the other. In fact, they may make reverse operation
horrible. Also, radially-aligned brushes (straight in toward the
center of the shaft) are great for motors that will be run
bi-directionally. However, leading or lagging brush angles (the
manufaturer will sometimes tip the top end of the brushes off the
cross-section-center-line of the shaft) may also make reverse rotation pretty
funky.
ICE vs. EM: Darryl is
right about the 4:1 ratio...lot's of folks will have different opinions on
this. The most common ration I've seen is 5:1; however, Darryl's 4:1
ratio (ICE hp to EM hp) is "safer," and I'd go work with that.
That's my two cents...Good Luck!
TJWilhelm
----- Original Message -----
Sent: Sunday, March 07, 2004 12:30 PM
Subject: Re: (ET) ICE to electric
conversion
> "Todd Lynch" <jd4020d_69 hotmail com>
wrote:
>
> > Hi all,
> >
> > I have been
watching the list for a while and have looked for an Electrak
> > for
sale in southern Minnesota with little success. With all the talk
about
> > updating Electraks to use a more modern controller, I was
think about how much
> > more it would take to convert an ICE garden
tractor to electric. I already have a
> > John Deere 112, of
approximately the same era the Electrak was made, with a bad
> >
engine, along with a mower, tiller, and sickle mower. I was thinking of
mounting
> > an electric motor where the current ICE engine is mounted
to run the accessories,
> > and mount an separate motor by the
transmission to drive the wheels, any thought?
> >
> > I
would greatly appreciate any thought or recommendations you might have
>
> such as size and type of motor would work best for this type of application
> > etc...
> >
> >
> > Thanks,
>
>
> > Todd Lynch
>
> Todd,
> such conversions
are certainly possible, and have been done.
>
> Some things to
consider.
>
> Hydrostatic transmissions waste a lot of energy as
heat (which is why they usually
> have lots of cooling fin area on their
casings). I don't know your proposed donor,
> but if it has a
hydrostatic transmission, I'd look for another base for your
>
conversion. However, given it's vintage, I expect it is not
hydrostatic.
>
> Every gas tractor I am familiar with uses a single
engine for both traction and
> powering the devices. You will need
to size your electric motor accordingly. Most
> electric tractors
have used multiple motors; one for traction and one or more
> additional
motors to power other devices. Gasoline engine and electric motor
>
rating
> systems are different. Gasoline engines are rated on the
maximum power they can
> produce under optimized conditions.
Electric motors are usually rated based on the
> power they can produce
continuously for one hour, often under specific less-
> than-ideal
conditions. My rule of thumb is 4:1 - if an electric motor is rated at
> 1
> hp, it is roughly equivalent to a 4 hp gasoline engine for
power. Not everyone
> will
> agree with that. For a
lawn or garden tractor, I think you should be looking for a
> 2-4 hp
electric motor. For comparison, the electric motors used in golf carts
for
> many years were nominally rated about 2 hp. The electric motor
will typically
> accept power demand over its ratings for short periods
without problems - so long
> as
> it can disperse the waste heat
afterward.
>
> Presumably you plan to power your tractor with
batteries. They are a DC electrical
> source. Further, most
tractor applications want relatively steady-speed operating
>
capabilities. Therefore, I recommend you look for a shunt-wound,
compound-wound or
> separately-excited DC motor (rather than a
series-wound motor or AC motor). There
> are universal motors, but I
have not encountered them in 10 hp (peak) and up power
> ratings.
Permanent magnet motors are usually equivalent to shunt wound and would
>
be
> acceptable, but again, I'm not aware of many of the right size for a
garden
> tractor.
> I'm not going to be much help on sources,
but I'm sure other listers can help out
> in that department. While
golf cart motors are about the right ratings, they are
> usually
series-wound and often use a mated gearbox to provide bearing support
for
> the output shaft, so are not usually good candidates for this sort
of application.
>
> Power from the batteries to your electrical
devices will be delivered in watts,
> which is volts x amps. So for
the same power, more volts means less amps. Less
> amps means
lighter gauge wires. On the other hand, anything above 48 volts DC
can
> be nasty. The Coast Guard permits up to 48 volts around water
without special
> permits. The new generation of golf carts are
standardizing on 48 volts. The Elec-
>
> Traks and their
brethren standardized on 36 volts. The traditional golf carts
>
standardized on 36 volts. The next generation automotive accessory
standard
> (sometimes referred to as 42 volts) is really a 36 volt nominal
standard. Much of
> today's materials handling equipment runs on 36
or 48 volts. Many of the early
> electric cars (early 20th century)
ran on voltages between 36 and 48 volts. A lot
> of experience has
led back to the same conclusions. I recommend you benefit from
>
that experience and stay with a voltage in the same range. This will also
provide
> you with some parts sources for various electrical components
you will need
> (batteries, fuses, motors, contactors, controllers,
chargers, etc).
>
> So, look for a motor with an operating voltage
rating in this range. Next, find
> out
> what the operating
speed for the motor is at nominal voltage. I expect you will
> want
something in the area of 3000 rpm as the rated speed. If it is
signficantly
> different, you will likely want to do some belt and pulley
gearing to get this
> effective speed at the point where your electric
motor joins up to the transmission
> and power-take-off. You might
have lots of torque, but if the RPM is too slow, you
> won't be happy with
the performance of your machine. (If it's too fast, you'll
>
have
> some different issues, but you still won't be happy.)
>
> While the venerable ETs used contactor and resistor controllers, I
would recommend
> use of a modern solid-state controller if your budget
permits. If not, resistors
> and contactors will work.
>
> Don't skimp on gauges (voltmeter and ammeter minimum), fuses and at
least one
> manual power disconnect.
>
> Most electric
motors make electric reversing pretty simple to implement.
However,
> if your existing donor has a mechanical reverse in good working
order, I would
> stick
> with that, and go with the simpler wiring
that goes with running the electric motor
> in one direction all the
time.
>
> The electric motor will have to be mounted to turn in the
same direction as the old
> gasoline engine did. I don't play with
many small gas engines, but I think most
> spin counter-clockwise (CCW) as
viewed from the output shaft. And while most
> electric motors can
be reversed, they usually do have a preferred direction of
>
operation.
>
> Once you have a bit of a plan, or questions about
suitability of components, I
> recommend you share them here. There
is a truly amazing amount of knowledge and
> ingenuity (and a little bit
of lunacy) available here. In general, a very helpful
> and sharing
community on this list.
>
> These links might provide some
inspiration.
>
> http://www.austinev.org/evalbum/038.html
>
> http://www.austinev.org/evalbum/196.html
>
> http://www.austinev.org/evalbum/411.html
>
> http://www.austinev.org/evalbum/065.html
>
> http://www.austinev.org/evalbum/216.html
>
> http://www.renewables.com/tracpage1.html
>
> Hope this was helpful.
>
> Darryl
McMahon
>
>
> ------- End of forwarded message
-------
>
>
>
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