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RE: (ET) Re: new electrics
William, if I told you what we pay for a battery or power electronics, you
would be floored. What I mean by cheap is tens of dollars for the whole
battery pack. The cost of materials won't let that happen for a flooded
lead-acid battery. Any efficiency improvement of AC to what GE did is
marginal. GE did a good job, at a low price, and did better than break
even. The problem is pencil-pushers always compare profit to what the
same money would do as simple investment, and simple investment won. It
still would today.
Larry Elie
-----Original Message-----
From: William Korthof [mailto:wkorthof earthlink net]
Sent: Friday, February 20, 2004 11:46 AM
To: Elec-Trak
Subject: RE: (ET) Re: new electrics
The cheap batteries have been around for quite a while...
golf cars have created this market: a pack of six US2200
or T105 batteries cost just a few hundred dollars (~$300).
I think the improved power electronics and motor choices
(in volume, a 3-phase inverter is cheap enough to allow
use of 3-phase AC motor). An AC motor driven by normal
vector drive inverter obviates the need for multiple gears.
Regenerative braking is also easy with AC drive. All the
above would result in significantly improved efficiency vs
GE Electrak-era hardware.
Any necessary 12vdc accessories can be operated
directly from a DC-DC converter. Lighting and markers
could use LEDs and compact fluorescent lamps.
Todays power electronics also make it easy to have a
powerful automatic charger that is "plug and play" to a
standard outlet and provides most of a charge within
2-3 hours. Faster, smarter charging, improved efficiency,
and more completely balanced battery discharging
(vs electrak taps) would lower the AC power use, extend
run time, and lengthen battery performance and pack life.
In addition, todays inverters could easily provide a nice
supply of 120 VAC for portable power tools.
I do think that a modern electric tractor is an unexplored
product with a significant un-served market.
/wk
At 09:46 AM 2/20/04 -0500, Elie, Larry (L.D.) wrote:
>Hydrostatic is 65 to less than 80%, depending on many factors including
>temperature. It's used on gas tractors for connivence, nothing
>more. Hydrodynamic (car automatic) can go much higher, but isn't really
>variable speed at all; just shift-on go.
>
>It's always funny when our 30 year hindsight realizes that people 30
>years
>ago weren't dumb. If electric tractors rise again, it will be because
>someone has a cheap battery or ultra-cap... or perhaps uses a cheap fuel
>cell. This market is already poisoned, and no large marketing guy will
>touch it. Once business people 'know' that no one will buy something,
>they stop trying. Another example: Diesels have 50% market penetration
>in Europe at higher fuel price. In the US it's 5%, because GM failed
>marketing it in 1980, and now everyone 'knows' that no one will buy
>them. Service is part of that. They tried, but not well. People paid a
>large premium to buy the early ones, and then averaged over $1,000/year
>for repairs. I'm afraid Honda or Toyota may poison the electric market
>for the next 25 years too. If they start passing on real their costs,
>they will indeed kill the market. I'm glad GM pulled out before they
>poisoned the electric market. No one will take large los!
> ses for long before they pass them on or pull out, and pulling out to
> give others a chance is the BETTER choice for everyone else.
>
>Larry Elie
>
>
>-----Original Message-----
>From: Ralph & Elaine Vogan [mailto:ralphgv centurytel net]
>Sent: Friday, February 20, 2004 3:33 AM
>To: Elec-Trak
>Subject: Re: (ET) Re: new electrics
>
>
>Does anyone know the efficiency of a hydrostatic drive? Use a single
>speed
>motor and the drive for forward, reverse, and speed changes. I have an
>old
>White ice tractor with a very small hydrostatic drive unit bolted to the
>differential. It has plenty of power. Or a hydrolic pump & motor to
>drive
>the blades?
>
>Ralph V
>
>
> > With all this talk about new ETs and better or cheaper ways to make
> > them
> > please remember that due to the limited energy storage on board our
>tractors
> > efficiency must be paramount.
> >
> > V belt drives tend to be only 90-95% efficient when everything is in
> > good
> > condition and clean.
> >
> > Friction drives are 80-90% efficient.
> >
> > Chains, again in good condition, are 98 % efficient, but high
> > maintenance
>to
> > keep them in good shape in a tractor application. Notice that they are
>not
> > used except in high torque attachments like the snowblower. A worn,
> > dry,
> > and/or rusty chain can have efficiencies as low as 60-70%. The wasted
> > energy turns to heat and destruction of what is left of the chain and
> > sprockets.
> >
> > Direct drive, like the mower decks, are 100% efficient.
> >
> > GE used VX series V belts for the traction motor because the VX series
> > V
> > belts are more efficient than the old A/B/C/D series V belts. If the
> > new
> > Poly V belts, which are like the serpentine belts on modern cars, had
> > been
> > available when the Elec Traks were designed they would have been used
> > preferentially over VX belts.
> >
> > What GE did was make a whole series of design choices to keep
> > efficiency
> > high. Where they lost efficiency was in the motor controls, and that
> > was
> > mainly a limitation of affordable DC drive technology of that time. If
>you
> > were, in your new tractor, to use a friction drive for the traction
> > motor
> > and belts in the mower deck, and then allowed for lack of maintenance,
>you'd
> > find extra losses of 10-25% after 1 or 2 years of service. I mean
> > 10-25%
> > higher losses than in a tractor with direct drive to the blades, and a
>high
> > efficiency belt somewhere in the traction drive.
> >
> > With respect to protecting the mower motor with a circuit breaker:
> > This
> > will not work well with a permanent magnet motor. In permanent magnet
> > motors there is some critical armature current above which you will
> > demagnetize the magnets. The friction washers, while crude, act as a
>torque
> > limiting clutch. By limiting torque, you effectively cap the armature
> > current. If you use a circuit breaker alone the current can, and most
> > likely will, pass well above that critical current before the breaker
>trips.
> >
> > Steve Naugler
> > snaugler earthlink net
> >
> >
> >
> > _______________________________________________
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> > Elec-trak cosmos phy tufts edu
> > https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak
> >
>
>
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