Re: (ET) Re: new electrics

["Herb Crary" <jhcrary comcast net>]

Good analysis. My first comment is that using 12v instead of 36 volts means
that everything uses three times the current for the same power
level----wires, cables, switches, breakers, relays or contactors, etc. That
raises the cost, perhaps the space required, etc.

Herb Crary
Boulder CO

----- Original Message ----- 
From: <Jeremy Gagliardi com>
To: <elec-trak cosmos phy tufts edu>
Sent: Friday, February 20, 2004 3:31 PM
Subject: RE: (ET) Re: new electrics


> Given the current conversation of "How do I build a better ET?" or "If 
> ETs
were
> built to modern standards, what would it be?"  Well, if you're 
> interested,
I've
> given this some thought lately, and here is what my criteria would be
(read that
> to mean, if I were the average consumer, this is what I would buy at
Sears).
> Now, this is mighty lengthy, because it's an essay, not just an e-mail.
Read
> on, if you're interested, discuss if you like offline to
Jeremy Gagliardi com or
> online if ET related.
>
> For the sake of discussion, let's put all of the mechanical and 
> structural
> elements aside, and talk only about the electric components, since those
are the
> only major difference from an ICE tractor.
>
> Next, let's use the GE Elec-Trak E20 as the example tractor.
>
> What are the major components of the ET?
>  - Batteries
>  - Charger
>  - Drive motor
>  - Front Lift
>  - Controls (circuit boards and relays)
>  - PTO receptacle
>  - Accessory receptacle
>  - Circuit breaker assembly and main disconnect switch
>  - Lights and Horn
> I am going to add one component that I think should be standard:
>  - AC Inverter
>
> Now, to build the tractor to modern standards, I put forth that these
goals must
> be met:
>  (1) Use standard stock item parts, most of which can be found in any
automative
> or tractor store
>  (2) The system should be all 12V DC so that the cheapest, most common
> automative parts can be used.
>  (3) The system should be simplified in 2 ways:
>    (a) Simple to assemble and disassemble.
>    (b) Simple to operate
>
> How does one meet the above goals?
>  - Use standard motors:
>    - The drive motor would have to be beefy but operate on 12V.
>    - The front lift I think could be powered by a 12V winch motor,
perhaps --
> something with a lot of power, but not a lot of speed.
>
>  - If possible, use cheap batteries.
>
>  - Use simple batteries:
>    - The batteries should be sealed and require no maintenance.
>    - Each battery should be easily pulled out and replaced.  That means
the
> power cables should have a simple attachment to the battery terminals -- 
perhaps
> a clamp type attachment.  For batteries with standard posts, you could
make an
> assembly that keeps the +&- terminals held apart with a bar and keeps 
> them
in
> the right order, + to +, - to -.  Make it foolproof so the batteries
cannot be
> installed backwards.
>
>  - Use a simple charging system -- There are really 3 goals here:
>    - The charger should simply connect to the batteries and allow you to
plug it
> in to AC.  It would simply charge when needed, and shutoff automatically
when
> not needed.  No timer and no need to monitor.  It should work on a
standard 15A
> AC outlet.
>    - There should be an identical charger that can sit in your garage.  I
have
> this idea that it would attract more customers if the batteries could be
> changeable, so that if one pack poops out, you can swap with a fully
charged
> pack, and get off and going again, just like refilling the gas tank, or
more
> simply like changing the battery of a modern power tool.  To achieve this
goal,
> there would be standard batteries on-board and a "light" pack that anyone
who
> could lift say 20 pounds could pull out and replace.  When the on-board
pack
> poops out, the tractor switches to using the spare pack (sort of akin to
the
> spare gas tank on a van or truck).  When the extra pack poops out, you
pull it
> out and plug it into the external charger, and unplug and install the
charged
> pack.  If the external charger is of the "quick" charge type, you could
> potentially play swapsies all day long, and never have the stigma that
once the
> batteries are dead, your work is done, nor the "stranded tractor" 
> syndrome
> (simply carry over a spare pack and get the tractor back to the garage).
> Customers who would use the tractor heavily could buy even another 
> charger
&
> pack combo and have more than one pack on charge for immediate use.  In
order to
> do this, the spare pack would have to be relatively lightweight.  It 
> could
> potentially be a single 12V battery that has enough juice to drive & mow
for
> about say 20-30 minutes.  The on-board pack could probably be 4-6 12V
batteries
> that could last for say 2 hours.  Most customers would probably never
require
> the spare pack.  The customer that would need to operate for longer than 
> 2
> hours, would probably buy the extra charger/battery combos.  Potentially,
you
> could make all batteries easily swappable, so every battery could be
swapped for
> extended use.
>    - Offer a DC-to-DC charger for those who are off-grid.  If someone
already
> has a solar system, simply offer a DC charge controller as a replacement,
or
> possibly an add-on for the AC charger.  Perhaps, sell the tractor as 
> truly
green
> by bundling the DC charge controller as a standard component.  Perhaps,
bill the
> tractor as dual charging, either from AC or from a DC system.
>
>  - The controls should be all solid state and use changeable components.
Fewer
> moving parts means higher reliability.  If a relay burns out, simply
unplug it
> and replace it with a store bought replacement.  If the whole unit fails,
simply
> unplug the board from the tractor and plug in a new one from the
manufacturer
> (sort of like replacing a component in your computer -- the concept is
open up
> the access door, unplug the wiring assembly, swap the board, plug in the
wires,
> and stow it again).  Never should a user have to solder or use wire 
> tools.
A
> user would have to use no tool any more complicated than a screw driver.
>
>  - The control assembly should have a simple interface.  The really 
> simple
> switches and double meter system used on the E20 is a great assembly.
Although,
> instead of an analog meter, I would replace it with digital (extreme
temperature
> tolerant, of course).
>
>  - For the truly geeky, you should be able to pop out the existing meter,
and
> pop in a new one with more control, programmability, and features.  The
> interface board when removed should allow the user to simply pop out a
switch
> and replace it with a new one without having to use a soldering iron.
>
>  - Similar to the controls, every major component of the tractor should 
> be
> easily changeable.  Wires should be bundled together according to use and
> attached to the tractor with pop-in/pop-out type holders.  Every wire
bundle
> would terminate in a quick-connect type plug.  Potentially, certain
components
> could be easily popped out and used separately from the tractor.  The
Inverter,
> for instance, could be unplugged and used in your car.  The charger could
be
> removed from the tractor and used to charge a spare battery.  Afterall,
why do
> you need a charger in the tractor when it's being used?  Potentially, 
> even
the
> wire bundles would be easily changeable.  If a mouse chews threw a wire
bundle,
> simply unplug that bundle at both ends, pop it out from the body
connectors, and
> replace it with a manufacturer provided replacement part.  Light bulb
burnt out?
>  Pop out the bulb, go to your local auto store and buy a new one, and pop
it in.
>
>  - I think the accessory receptacle should be simply the AC plug on the
> inverter.  There's no sense in getting into the business of selling
propietary
> attachments that can only plug into your tractor.  Simply go to Sears and
buy an
> AC powered string trimmer, and plug it into the AC plug on the tractor.
See
> next item...
>
>  - All components would run on native 12V DC.  There would be no need for
bulky,
> expensive, and energy-steeling DC-to-DC converters.  Plus, with the 
> system
being
> 12V native, you could have a standard car power socket in the dashboard
(or
> wherever convenient) and use standard automotive accessories, like
handheld
> flood lamps, a radio with a car-adapter, a tire inflator, etc.
>
>  - The PTO receptacle would be for the truly beefy attachments -- mower,
snow
> thrower, etc. -- all 12V.
>
>  - The circuit breaker assembly should be centralized to include all
components.
>  It should be circuit breakers and not fuses.  But, if the circuit 
> breaker
ever
> fails, simply unplug it and replace it with a new one.
>
>  - I would say make the tractor grounded, like most cars, for
compatibility.
>
>  - For the front lift, possibly have it be a dual-purpose unit; one mode
would
> be the simple lift, and in the other mode, it would rotate a drum of wire
to
> operate as a winch.  This would increase the versatility of the tractor 
> if
a
> standard item.
>
> This has been my dream, and now I have voiced it.
>
>
> (---------------------------)
>  mailto:Jeremy Gagliardi com
>  http://Jeremy.Gagliardi.com
> (---------------------------)
>
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