EV Digest 6173
Topics covered in this issue include:
1) RE: Motor selection for 2KW PV solar only drag race = LONG
by "Offgrid Engineering" <[EMAIL PROTECTED]>
2) Re: "Files" section on Yahoo Groups?
by "David Roden" <[EMAIL PROTECTED]>
3) Re: Leaking motor, an'Stuff
by "Bob Rice" <[EMAIL PROTECTED]>
4) Re: 2 Segways spotted
by "Roderick Wilde" <[EMAIL PROTECTED]>
5) ELECTRO-SOLAR HYBRID
by Geopilot <[EMAIL PROTECTED]>
6) Re: CVT for solar EV, RE: Motor selection for 2KW PV solar only drag
race = LONG
by Geopilot <[EMAIL PROTECTED]>
7) Re: Wierd and Wonderful cars WAS Newbie question about batteries
by Geopilot <[EMAIL PROTECTED]>
8) Re: CVT for solar EV, RE: Motor selection for 2KW PV solar only drag
race = LONG
by Geopilot <[EMAIL PROTECTED]>
9) Re: CVT for solar EV, RE: Motor selection for 2KW PV solar only drag
race = LONG
by Geopilot <[EMAIL PROTECTED]>
10) Re: Leaking motor, an'Stuff (Edison Stout)
by <[EMAIL PROTECTED]>
11) Re: CVT for solar EV, RE: Motor selection for 2KW PV solar only drag
race = LONG
by Geopilot <[EMAIL PROTECTED]>
--- Begin Message ---
Thanks to Lee, Doug, Peter, Jerry and all the others who added to the
discussion...
The high school team is leaning toward using a CVT, with a backup using a
bike 3 speed hub. The panels and the motor will be on order by next Friday.
Doug has the only motor solution other than the AGNI at
http://www.ecycle.com/motorgenerator.html, so we are down to two
possibilities.
If anyone has had any experience with either the AGNI motor or the ecycle
brushless, I would love to hear.
The race is next June, I'll post the results then!
Thanks again..
Tim Economu
team advisor
-----Original Message-----
From: jerryd [mailto:[EMAIL PROTECTED]
Sent: Sunday, November 26, 2006 3:26 AM
To: [email protected]
Subject: CVT for solar EV, RE: Motor selection for 2KW PV solar only drag
race = LONG
Hi Tim and All,
The first car to cross the US, The Wilson, had a CVT made by
using a friction wheel against a drive disc, moving the driven wheel closer
and farther from the centerline to change gears. And it was one of the few
things not to break!!! Using a rollerblade wheel as the drive wheel and an
alum disc, like used for table disc sanders or made from scratch with a
pully and an Alum plate, ect should work well for your short term needs.
Hope This helps
Jerry Dycus
----- Original Message Follows -----
From: "Offgrid Engineering" <[EMAIL PROTECTED]>
To: "'Lee Hart'" <[EMAIL PROTECTED]>, <[email protected]>
Subject: RE: Motor selection for 2KW PV solar only drag race = LONG
Date: Sat, 25 Nov 2006 18:02:49 -0800
>Hi Lee:
>Sorry I did not give a very complete reply earlier. I'll try to be more
>thorough now that I have time. I'll use your
>numbers:
>
>1. I totally agree array direct as soon and as long as possible will be
>the best course. The car must peak power trace the array, and "peak
>efficiency track" the motor to have max acceleration. And yes it is
>well understood the panels peak power and continuous power, unlike
>batteries, is the same thing.
>2. Yep Vmp = 56V and 35.7 amps
>3,4. The CVT is a solution that can keep the motor at the same RPM, and
>it is a possible solution here. We have modeled the CVT using a number
>of different pulley sizes and shapes. While we will continue to work on
>this, we are a bit dubious that it will be reliable, efficient, give
>high repeatability, have an operation curve close to what we need, be
>able to be built by high school students. WE are interested if anyone
>has built a simple efficient CVT, and we won't give up developing ours,
>thanks for the ideas!
>
>I was assuming a buck pwm would be the better choice, and my
>calculations given earlier assume that to be the case, but this may
>turn out not to be true. The motor needs to accerate to full rpm in the
>very beginning, and would you like to use max array current of about 36
>amps or maybe 150 amps, given the same drive ratio? Now one could use a
>combination of say DC-DC converter making 12V at 150 amps to get RPMS
>up and then switch to a CVT, and we are looking at that too. But I do
>believe in KISS.
>
>If a CVT were, used, I agree that the pmdc motor would be the better
>choice, for the high efficiency, but if a pwm controller is used, using
>the controller as the transmission, maybe the series motor is not such
>a bad choice. Once I get the curves (have an email to ADC) I can put
>them in the model to compare to AGNI.
>
>Thanks again...
>
>Tim
>
>
>-----Original Message-----
>From: Lee Hart [mailto:[EMAIL PROTECTED]
>Sent: Saturday, November 25, 2006 1:29 AM
>To: [email protected]
>Subject: Re: Motor selection for 2KW PV solar only drag race = LONG
>
>Offgrid Engineering wrote:
>> I think PMDC is a good choice, but a series motor might
>be good too
>
>Your solar dragster is a special-case problem, because your PV panels
>are the only source of power, and they are a constant power device.
>Loading them heavier or lighter than optimum produces less power, which
>means you accellerate slower (and lose the race).
>
>So, you want your motor/controller/transmission to load the panels at
>(about) their peak power point throughout the race, as the car
>accellerates from 0 to maximum speed.
>
>Here's how I was approaching the problem:
>
>1. The most efficient controller is NONE. A DC motor, connected
> directly to the PV panels. The throttle is just an "on/off" switch.
>
>2. The peak power point occurs at a particular voltage and curent.
>
>3. So, the motor will run at a constant voltage and current. That
> implies constant rpm and torque, regardless of vehicle speed.
>
>4. And that implies a CVT (continuously variable transmission).
>
>5. Do some calculations using your PV panel's peak power (2kw?),
> motor efficiency at that power (90%?), and the weight of the
> car+driver. Find the resultant wheel rpm vs. time with this
> constant horsepower.
>
>6. Now, using the motor's constant rpm at this power, you can compute
> the CVT ratio as a function of time, to keep the motor loaded to
> its correct speed and torque.
>
>7. Design the pulleys of your CVT to achieve this change in ratios.
> You can have the ratio change linearly by using a flat band, or
> have it change exponentially with a wire that winds up zig-zag
> fashion between two unequal-width spools.
>
>> In Excel we modeled the "simple CVT" you suggest and it is a fairly
>> linear proportion curve. When you overlay this curve over the
>> exponential torque curve from a motor, the two do not line up very
>> well.
>
>You're missing that you have a fixed power from the PV panel.
>Therefore, the motor has only one operating point.
>There is no torque-speed curve; just one operating point for maximum
>accelleration.
>
>Now, you could use a PWM controller to vary motor voltage while
>maintaining peak power loading of the PV panels. But I think you will
>find that this automatically means running the motor at points away
>from its peak efficiency.
>
>But, it still might "win" if the extra losses in the controller and
>motor were less than losses saved by replacing the CVT with a fixed or
>X-speed transmission.
>--
>"Never doubt that the work of a small group of thoughtful, committed
>citizens can change the world. Indeed, it's the only thing that ever
>has!" -- Margaret Mead
>--
>Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net
>
--- End Message ---
--- Begin Message ---
On 26 Nov 2006 at 13:29, Craig Burton wrote:
> I've seen mention of posting/retrieving files to the Files section on
> Yahoo Groups. I tried joining one such group and was denied access.
There are no official relationships between the EV list and any Yahoo or
Google group. They're not official EVDL file repositiories. If you have
access to some EV-related Yahoo or Google group and the owner is OK with it,
then you can upload files there, I guess, and post a link to them here.
But keep in mind that a fair number of EVDL members are put off by the
privacy concerns with these operations, and won't join Google or Yahoo just
to get your file.
I don't know about any Google groups, but the two Yahoo groups are
>unofficial< EVDL archives. They're "read only" - that is, their only
purpose in life is to be archives of messages posted to this list. You
can't join them, post to them, or create files there.
http://tech.groups.yahoo.com/group/ev/
http://autos.groups.yahoo.com/group/ev-list-archive/
So how can you get files across to EVDL readers? I can think of 3
reasonably practical ways.
1. Upload the file to your own website, and post a link here. If you do
this, please remember that the list is archived in several places (not just
Yahoo). Someone may read your message and want your file 5 or 10 years from
now! If you're not planning to host that file indefinitely, please include
an expiration date after which the file will no longer be available.
2. Use one of the online commercial file repositories. I think there are
about 22% more of these than there are stars in the sky. Some, such as
yousendit.com, even allow huge files. This is less desirable than the
method above, because most of these repositories will delete your file if
it's not fairly frequently downloaded.
3. Email it to me as an email attachment (or otherwise get it to me; contact
me for details) and I'll post it at evdl.org. Files posted there may
reasonably be expected to stay where they are until I'm dead and no longer
paying hosting fees and/or operating a server, or other nearly-as-dire
circumstances conspire to demolish evdl.org.
If you want to send me a file, look at the bottom of this page for my
private contact information :
http://www.evdl.org/
I was going to recommend using the file storage at evforge.net, but that
website seems to have vanished into the highland mists. Although it's still
registered until its expiry of 15 December, it has no current DNS
assignment. Either something is broken, or (more likely, I'm sorry to say)
evforge.net has joined the list of EVDL resources that didn't catch on with
list members, and have been abandoned.
David Roden - Akron, Ohio, USA
EV List Assistant Administrator
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--- End Message ---
--- Begin Message ---
Hi Storm;
If your worried about a leak, just put a cookie sheet on the carpet under
the motor<g.>All kidding aside your probably reading through carbon dust
from the brushes? Blow the motor out with compressed air and see if that
makes a differance? Don't breathe that shit, though!Get a cheapo nose air
filter from Tru-Value, or Home Despot. I wouldn't worry about it, if the
damn car RUNS well, be happy!Oh yeah? Are the tops of the batteries clean?
If not hose them clean, dry with the air gun, you ALWAYS unless ya pop for
Optimas or Orbitals ,have the crud, water or damp tops of the floodie badd-
eries. This is a sloooooow short circuit.Leading to Lee Hart's famous "
Edison Stout, Who Didn't Check His Batteries Out" Poem!There MUST be a link
for that, plus the In Season "Christmas Story"?
My two ohms worth.
Bob---- Original Message -----
From: "Storm Connors" <[EMAIL PROTECTED]>
To: "List EV" <[email protected]>
Sent: Sunday, November 26, 2006 2:47 PM
Subject: Leaking motor
> I am reading 70V between the positive side of my pack and the chassis
ground. If I remove the negative lead to the motor, there is no voltage
between the pack and ground. If I close the contactor which is at the
positive end of the pack, I read 25v from the negative end of the pack to
the chassis and 50v from the positive end of the pack to chassis.
>
> I assume this is a problem. Am I going to have to go inside the motor to
find out what is leaking? FWIW, it seems to be running fine. As a Jeep
owner, I know that is the sure sign of a major problem. Any time it is
running fine, look out.
>
> Thanks,
> storm
>
>
>
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.1.409 / Virus Database: 268.14.16/552 - Release Date: 11/26/06
>
>
--- End Message ---
--- Begin Message ---
Rod, they were probably on the trail because a lot of money was spent
lobbying state governments nationwide to make a law specifically just for
one brand of vehicle. Kind of like making a law that you can only drive
Fords on the highway. I know this sounds utterly ridiculous but it is
absolutely true. Here is the law from here in Washington State, RCW
46.04.1695
An "electric personal assistive mobility device" (EPAMD) means a
self-balancing device with two wheels not in tandem, designed to transport
only one person by an electric propulsion system with an average power of
seven hundred fifty watts (one horsepower) having a maximum speed on a paved
level surface, when powered solely by such propulsion while ridden by an
operator weighing one hundred seventy pounds, or less than twenty miles per
hour.
These are allowed on sidewalks and bike paths in many states although they
have been starting to legislate them off sidewalks. I have a great new idea.
How about a self balancing device balanced by yourself with two wheels, one
in front of the other. It would take up much less width on a trail :-)
Roderick Wilde
PS: I really like the term in the law about average power. How much more
vague could they be?
----- Original Message -----
From: "Rod Hower" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Sunday, November 26, 2006 6:20 PM
Subject: 2 Segways spotted
I went on a 20 mile bike ride today on a scenic route
that is a bike path that parallels the Ohio canal boat
route that was the main transport route for goods
during the 1800's. I passed 2 physically able guys
riding Segways down the path. It was cool seeing the
EV's, but I wondered why they were riding on this
pedestrian/bike path. EV's are nice transport, but I
wonder why they were riding on a bike path? Perhaps 2
guys with a really cool toy.
Rod
W8RNH
--
No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.1.409 / Virus Database: 268.14.16/552 - Release Date:
11/26/2006
--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.409 / Virus Database: 268.14.16/552 - Release Date: 11/26/2006
--- End Message ---
--- Begin Message ---
Make sure you see the photos at the site. it is quite beautiful but
sparse in a formula 1 kind of way.
http://www.autobloggreen.com/2006/09/29/paris-motor-show-venturi-astrolab-electro-solar-hybrid/
The third vehicle that Monaco based car-maker Venturi is showing is
peculiar looking tandem two seater called the AstroLab. Venturi claims
it is the first electro-solar hybrid vehicle. It can charge its
batteries either from the sun via the flat upper surface covered with
photo-voltaic cells or by plugging it into an outlet. Questionable
aesthetics aside this is a technologically-interesting vehicle. The
manufacturer claims that even the carbon dioxide emissions produced by
the production process will be offset by other environmental actions,
hence the label "The CarbonNeutral Company". More details from Venturi
after the jump.
ELECTRO-SOLAR HYBRID
HYBRIDE ELECTROSOLAIRE
With 3.6 m2 of photovoltaic cells giving an exceptional yield of 21%,
and covered by a film composed of nano-prisms enabling denser
concentration of solar energy, Astrolab is the first high-performance
solar vehicle to be commercialised in the world.
Capable of working with very little energy (16 kWc engine) and of
recharging even when in motion, this vehicle of another era does not
need to be permanently exposed to the sun in order to move. Its
last-generation NiMH Venturi NIV-7 batteries – liquid cooled – in fact
enable it to restitute stored energy, whether solar or from the
electricity supply, making it the first electro-solar hybrid vehicle.
With a top speed of 120 km/hr and autonomy of 110 km, Astrolab is a real
"Solar Commuter" making extensive trips on a daily basis.
CONSUMPTION = 0, EMISSIONS = 0
This is very first vehicle that consumes no fossile resources in order
to work : the emissions of CO2 required for its construction will even
be compensated for by evironmental actions.
A parallel can be drawn between Astrolab and a sailboat : both advance
silently while making best use of the elements provided by Nature. And
the piloting of both makes for sensations unlike any other.
To attain this level of performance while using very little energy,
Astrolab has been designed like a Formula 1 : its carbon monocoque
chassis is ultra-light and serves as an oversized protection cell
ensuring the safety of its occupants in the event of a collision. Its
profile recalls the aqua-dynamic design of great racing yachts.
--- End Message ---
--- Begin Message ---
Red snapper brand riding mowers used the same kind of drive.
I rode one for years and the thing took hills like a magnatraction car.
they are bullet proof and the rubber discs are so easy to replace IF
they ever wear out.
A simple hand lever slide the wheel on the disc and changed gears . the
lever locked into set notches with a spring for formal "gear" ratios but
it was really infinitely variable.
jerryd wrote:
Hi Tim and All,
The first car to cross the US, The Wilson, had a
CVT made by using a friction wheel against a drive disc,
moving the driven wheel closer and farther from the
centerline to change gears. And it was one of the few things
not to break!!! Using a rollerblade wheel as the drive wheel
and an alum disc, like used for table disc sanders or made
from scratch with a pully and an Alum plate, ect should work
well for your short term needs.
Hope This helps
Jerry Dycus
----- Original Message Follows -----
From: "Offgrid Engineering" <[EMAIL PROTECTED]>
To: "'Lee Hart'" <[EMAIL PROTECTED]>,
<[email protected]>
Subject: RE: Motor selection for 2KW PV solar only drag race
= LONG
Date: Sat, 25 Nov 2006 18:02:49 -0800
Hi Lee:
Sorry I did not give a very complete reply earlier. I'll
try to be more thorough now that I have time. I'll use your
numbers:
1. I totally agree array direct as soon and as long as
possible will be the best course. The car must peak power
trace the array, and "peak efficiency track" the motor to
have max acceleration. And yes it is well understood the
panels peak power and continuous power, unlike batteries,
is the same thing.
2. Yep Vmp = 56V and 35.7 amps
3,4. The CVT is a solution that can keep the motor at the
same RPM, and it is a possible solution here. We have
modeled the CVT using a number of different pulley sizes
and shapes. While we will continue to work on this, we are
a bit dubious that it will be reliable, efficient, give
high repeatability, have an operation curve close to what
we need, be able to be built by high school students. WE
are interested if anyone has built a simple efficient CVT,
and we won't give up developing ours, thanks for the ideas!
I was assuming a buck pwm would be the better choice, and
my calculations given earlier assume that to be the case,
but this may turn out not to be true. The motor needs to
accerate to full rpm in the very beginning, and would you
like to use max array current of about 36 amps or maybe 150
amps, given the same drive ratio? Now one could use a
combination of say DC-DC converter making 12V at 150 amps
to get RPMS up and then switch to a CVT, and we are looking
at that too. But I do believe in KISS.
If a CVT were, used, I agree that the pmdc motor would be
the better choice, for the high efficiency, but if a pwm
controller is used, using the controller as the
transmission, maybe the series motor is not such a bad
choice. Once I get the curves (have an email to ADC) I can
put them in the model to compare to AGNI.
Thanks again...
Tim
-----Original Message-----
From: Lee Hart [mailto:[EMAIL PROTECTED]
Sent: Saturday, November 25, 2006 1:29 AM
To: [email protected]
Subject: Re: Motor selection for 2KW PV solar only drag
race = LONG
Offgrid Engineering wrote:
I think PMDC is a good choice, but a series motor might
be good too
Your solar dragster is a special-case problem, because your
PV panels are the only source of power, and they are a
constant power device. Loading them heavier or lighter than
optimum produces less power, which means you accellerate
slower (and lose the race).
So, you want your motor/controller/transmission to load the
panels at (about) their peak power point throughout the
race, as the car accellerates from 0 to maximum speed.
Here's how I was approaching the problem:
1. The most efficient controller is NONE. A DC motor,
connected
directly to the PV panels. The throttle is just an
"on/off" switch.
2. The peak power point occurs at a particular voltage and
curent.
3. So, the motor will run at a constant voltage and
current. That
implies constant rpm and torque, regardless of vehicle
speed.
4. And that implies a CVT (continuously variable
transmission).
5. Do some calculations using your PV panel's peak power
(2kw?),
motor efficiency at that power (90%?), and the weight of
the
car+driver. Find the resultant wheel rpm vs. time with
this
constant horsepower.
6. Now, using the motor's constant rpm at this power, you
can compute
the CVT ratio as a function of time, to keep the motor
loaded to
its correct speed and torque.
7. Design the pulleys of your CVT to achieve this change in
ratios.
You can have the ratio change linearly by using a flat
band, or
have it change exponentially with a wire that winds up
zig-zag
fashion between two unequal-width spools.
In Excel we modeled the "simple CVT" you suggest and it
is a fairly linear proportion curve. When you overlay
this curve over the exponential torque curve from a
motor, the two do not line up very well.
You're missing that you have a fixed power from the PV
panel. Therefore, the motor has only one operating point.
There is no torque-speed curve; just one operating point
for maximum accelleration.
Now, you could use a PWM controller to vary motor voltage
while maintaining peak power loading of the PV panels. But
I think you will find that this automatically means running
the motor at points away from its peak efficiency.
But, it still might "win" if the extra losses in the
controller and motor were less than losses saved by
replacing the CVT with a fixed or X-speed transmission.
--
"Never doubt that the work of a small group of thoughtful,
committed citizens can change the world. Indeed, it's the
only thing that ever has!" -- Margaret Mead
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377,
leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
I was thinking of a pancake spring as a low speed city traffic start
stop regen device.
Very lightweight and efficient and simple for low speed s and recovers
virtually all energy from zero to 20 miles per hour or so.
David Dymaxion wrote:
On topic comment: On the spring thing, think about toy cars. Spring or flywheel
ones don't go very far, but electric ones can go pretty far.
Off topic comment: Believe it or not, the horse carriage rides in Salt Lake
City have emissions control devices on the horses. A small fabric ramp directs
the emissions down to a collector below the carriage.
----- Original Message ----
From: Bob Rice <[EMAIL PROTECTED]>
To: [email protected]
Sent: Saturday, November 25, 2006 11:58:41 PM
Subject: Wierd and Wonderful cars WAS Newbie question about batteries
----- Original Message -----
From: "Jack Murray" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Saturday, November 25, 2006 2:11 PM
Subject: Re: Newbie question about batteries
I can understand the goal, really poor efficiency is OK if cheap enough.
I'd suggest if you want homemade car power that you not use electricity,
consider a wind-up spring. How much range you can get from one that
isn't a massive safety issue I don't know, haven't done any calculations
Don't laugh, sport fans! It was tried over 100 years ago, with poor
success, to run streetcars. Back in the 1880's several companies tried
"Clockwork" cars. If ya ever had a Victrola apart, there is a big spring
cannister, that you wind up to play tunes.BTW if you EVer take one apart,
for God's sake,DON'T open it up!You will have a room full of angry, coil
springs glowering at you, in a nanosecond!!! Larger versions were proposed,
many linked together, wound up at the shop for the daze festivities. I
haven't found any range data, so I guess they wern't a roaring success<g>?A
bit high strung? Air cars DID work, back then, cars actually ran in Rome NY
on about a 8 mile run. A airpipe was laid along the route to charge them if
they ran out of breath, short of the end of the line. But then cable and
ELECTRIC cars came in.Electric seemed, back then, as far out as air and
clockwork cars.
At an Electa thon, some of the kids actually BUILT a spring car! Using
one of those fearsome garage door springs wound up, they went several
hundred feet!Was an interesting concept. Both air cars and Clockwork cars
could "Regen" like hell, though. Wind 'er up" could have had new meanings,
going down hill?Of course Steam was a serious contender for trolley
propulsion, but smoke and soot from them was frowned upon in city streets. I
guess not much was thought about about Horse Exhaust?! Rather have soot and
cinders than horse shit in the street! Anybody who has been in NYC for the
Central Park Buggy rides , on a hot day, can get a whiff of 19th century
traction!ANYTHING would be an inprovement over horses?EVen the newest ones
don't have emission controls, to this day.They are starting to clean up
Diseasels, too,nowadaze
My two horses worth.
Bob
____________________________________________________________________________________
Want to start your own business?
Learn how on Yahoo! Small Business.
http://smallbusiness.yahoo.com/r-index
--- End Message ---
--- Begin Message ---
this parts site has the cvt parts for sale for a snapper riding mower
with pictures.
dirt cheap!
http://images.google.com/imgres?imgurl=http://www.psep.biz/images/mower%2520parts/Snapper%2520Pic%27s/32%252036%2520and%252048%2520walk%2520behind.jpg&imgrefurl=http://www.psep.biz/store/snapper_mower_parts.htm&h=260&w=267&sz=12&hl=en&start=6&tbnid=Fqw0IM9_pphIaM:&tbnh=110&tbnw=113&prev=/images%3Fq%3D%2522snapper%2522%2Bmower%2B%26svnum%3D100%26hl%3Den%26lr%3D%26safe%3Doff%26sa%3DG
Red snapper brand riding mowers used the same kind of drive.
I rode one for years and the thing took hills like a magnatraction car.
they are bullet proof and the rubber discs are so easy to replace IF
they ever wear out.
A simple hand lever slide the wheel on the disc and changed gears . the
lever locked into set notches with a spring for formal "gear" ratios but
it was really infinitely variable.
jerryd wrote:
Hi Tim and All,
The first car to cross the US, The Wilson, had a
CVT made by using a friction wheel against a drive disc,
moving the driven wheel closer and farther from the
centerline to change gears. And it was one of the few things
not to break!!! Using a rollerblade wheel as the drive wheel
and an alum disc, like used for table disc sanders or made
from scratch with a pully and an Alum plate, ect should work
well for your short term needs.
Hope This helps
Jerry Dycus
----- Original Message Follows -----
From: "Offgrid Engineering" <[EMAIL PROTECTED]>
To: "'Lee Hart'" <[EMAIL PROTECTED]>,
<[email protected]>
Subject: RE: Motor selection for 2KW PV solar only drag race
= LONG
Date: Sat, 25 Nov 2006 18:02:49 -0800
Hi Lee:
Sorry I did not give a very complete reply earlier. I'll
try to be more thorough now that I have time. I'll use your
numbers:
1. I totally agree array direct as soon and as long as
possible will be the best course. The car must peak power
trace the array, and "peak efficiency track" the motor to
have max acceleration. And yes it is well understood the
panels peak power and continuous power, unlike batteries,
is the same thing.
2. Yep Vmp = 56V and 35.7 amps
3,4. The CVT is a solution that can keep the motor at the
same RPM, and it is a possible solution here. We have
modeled the CVT using a number of different pulley sizes
and shapes. While we will continue to work on this, we are
a bit dubious that it will be reliable, efficient, give
high repeatability, have an operation curve close to what
we need, be able to be built by high school students. WE
are interested if anyone has built a simple efficient CVT,
and we won't give up developing ours, thanks for the ideas!
I was assuming a buck pwm would be the better choice, and
my calculations given earlier assume that to be the case,
but this may turn out not to be true. The motor needs to
accerate to full rpm in the very beginning, and would you
like to use max array current of about 36 amps or maybe 150
amps, given the same drive ratio? Now one could use a
combination of say DC-DC converter making 12V at 150 amps
to get RPMS up and then switch to a CVT, and we are looking
at that too. But I do believe in KISS.
If a CVT were, used, I agree that the pmdc motor would be
the better choice, for the high efficiency, but if a pwm
controller is used, using the controller as the
transmission, maybe the series motor is not such a bad
choice. Once I get the curves (have an email to ADC) I can
put them in the model to compare to AGNI.
Thanks again...
Tim
-----Original Message-----
From: Lee Hart [mailto:[EMAIL PROTECTED]
Sent: Saturday, November 25, 2006 1:29 AM
To: [email protected]
Subject: Re: Motor selection for 2KW PV solar only drag
race = LONG
Offgrid Engineering wrote:
I think PMDC is a good choice, but a series motor might
be good too
Your solar dragster is a special-case problem, because your
PV panels are the only source of power, and they are a
constant power device. Loading them heavier or lighter than
optimum produces less power, which means you accellerate
slower (and lose the race).
So, you want your motor/controller/transmission to load the
panels at (about) their peak power point throughout the
race, as the car accellerates from 0 to maximum speed.
Here's how I was approaching the problem:
1. The most efficient controller is NONE. A DC motor,
connected
directly to the PV panels. The throttle is just an
"on/off" switch.
2. The peak power point occurs at a particular voltage and
curent.
3. So, the motor will run at a constant voltage and
current. That
implies constant rpm and torque, regardless of vehicle
speed.
4. And that implies a CVT (continuously variable
transmission).
5. Do some calculations using your PV panel's peak power
(2kw?),
motor efficiency at that power (90%?), and the weight of
the
car+driver. Find the resultant wheel rpm vs. time with
this
constant horsepower.
6. Now, using the motor's constant rpm at this power, you
can compute
the CVT ratio as a function of time, to keep the motor
loaded to
its correct speed and torque.
7. Design the pulleys of your CVT to achieve this change in
ratios.
You can have the ratio change linearly by using a flat
band, or
have it change exponentially with a wire that winds up
zig-zag
fashion between two unequal-width spools.
In Excel we modeled the "simple CVT" you suggest and it
is a fairly linear proportion curve. When you overlay
this curve over the exponential torque curve from a
motor, the two do not line up very well.
You're missing that you have a fixed power from the PV
panel. Therefore, the motor has only one operating point.
There is no torque-speed curve; just one operating point
for maximum accelleration.
Now, you could use a PWM controller to vary motor voltage
while maintaining peak power loading of the PV panels. But
I think you will find that this automatically means running
the motor at points away from its peak efficiency.
But, it still might "win" if the extra losses in the
controller and motor were less than losses saved by
replacing the CVT with a fixed or X-speed transmission.
--
"Never doubt that the work of a small group of thoughtful,
committed citizens can change the world. Indeed, it's the
only thing that ever has!" -- Margaret Mead
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377,
leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
sorry. this is the correct site
http://www.psep.biz/store/snapper_mower_drive_parts.htm
this parts site has the cvt parts for sale for a snapper riding mower
with pictures.
dirt cheap!
http://images.google.com/imgres?imgurl=http://www.psep.biz/images/mower%2520parts/Snapper%2520Pic%27s/32%252036%2520and%252048%2520walk%2520behind.jpg&imgrefurl=http://www.psep.biz/store/snapper_mower_parts.htm&h=260&w=267&sz=12&hl=en&start=6&tbnid=Fqw0IM9_pphIaM:&tbnh=110&tbnw=113&prev=/images%3Fq%3D%2522snapper%2522%2Bmower%2B%26svnum%3D100%26hl%3Den%26lr%3D%26safe%3Doff%26sa%3DG
Red snapper brand riding mowers used the same kind of drive.
I rode one for years and the thing took hills like a magnatraction car.
they are bullet proof and the rubber discs are so easy to replace IF
they ever wear out.
A simple hand lever slide the wheel on the disc and changed gears . the
lever locked into set notches with a spring for formal "gear" ratios but
it was really infinitely variable.
jerryd wrote:
Hi Tim and All,
The first car to cross the US, The Wilson, had a
CVT made by using a friction wheel against a drive disc,
moving the driven wheel closer and farther from the
centerline to change gears. And it was one of the few things
not to break!!! Using a rollerblade wheel as the drive wheel
and an alum disc, like used for table disc sanders or made
from scratch with a pully and an Alum plate, ect should work
well for your short term needs.
Hope This helps
Jerry Dycus
----- Original Message Follows -----
From: "Offgrid Engineering" <[EMAIL PROTECTED]>
To: "'Lee Hart'" <[EMAIL PROTECTED]>,
<[email protected]>
Subject: RE: Motor selection for 2KW PV solar only drag race
= LONG
Date: Sat, 25 Nov 2006 18:02:49 -0800
Hi Lee:
Sorry I did not give a very complete reply earlier. I'll
try to be more thorough now that I have time. I'll use your
numbers:
1. I totally agree array direct as soon and as long as
possible will be the best course. The car must peak power
trace the array, and "peak efficiency track" the motor to
have max acceleration. And yes it is well understood the
panels peak power and continuous power, unlike batteries,
is the same thing.
2. Yep Vmp = 56V and 35.7 amps
3,4. The CVT is a solution that can keep the motor at the
same RPM, and it is a possible solution here. We have
modeled the CVT using a number of different pulley sizes
and shapes. While we will continue to work on this, we are
a bit dubious that it will be reliable, efficient, give
high repeatability, have an operation curve close to what
we need, be able to be built by high school students. WE
are interested if anyone has built a simple efficient CVT,
and we won't give up developing ours, thanks for the ideas!
I was assuming a buck pwm would be the better choice, and
my calculations given earlier assume that to be the case,
but this may turn out not to be true. The motor needs to
accerate to full rpm in the very beginning, and would you
like to use max array current of about 36 amps or maybe 150
amps, given the same drive ratio? Now one could use a
combination of say DC-DC converter making 12V at 150 amps
to get RPMS up and then switch to a CVT, and we are looking
at that too. But I do believe in KISS.
If a CVT were, used, I agree that the pmdc motor would be
the better choice, for the high efficiency, but if a pwm
controller is used, using the controller as the
transmission, maybe the series motor is not such a bad
choice. Once I get the curves (have an email to ADC) I can
put them in the model to compare to AGNI.
Thanks again...
Tim
-----Original Message-----
From: Lee Hart [mailto:[EMAIL PROTECTED]
Sent: Saturday, November 25, 2006 1:29 AM
To: [email protected]
Subject: Re: Motor selection for 2KW PV solar only drag
race = LONG
Offgrid Engineering wrote:
I think PMDC is a good choice, but a series motor might
be good too
Your solar dragster is a special-case problem, because your
PV panels are the only source of power, and they are a
constant power device. Loading them heavier or lighter than
optimum produces less power, which means you accellerate
slower (and lose the race).
So, you want your motor/controller/transmission to load the
panels at (about) their peak power point throughout the
race, as the car accellerates from 0 to maximum speed.
Here's how I was approaching the problem:
1. The most efficient controller is NONE. A DC motor,
connected
directly to the PV panels. The throttle is just an
"on/off" switch.
2. The peak power point occurs at a particular voltage and
curent.
3. So, the motor will run at a constant voltage and
current. That
implies constant rpm and torque, regardless of vehicle
speed.
4. And that implies a CVT (continuously variable
transmission).
5. Do some calculations using your PV panel's peak power
(2kw?),
motor efficiency at that power (90%?), and the weight of
the
car+driver. Find the resultant wheel rpm vs. time with
this
constant horsepower.
6. Now, using the motor's constant rpm at this power, you
can compute
the CVT ratio as a function of time, to keep the motor
loaded to
its correct speed and torque.
7. Design the pulleys of your CVT to achieve this change in
ratios.
You can have the ratio change linearly by using a flat
band, or
have it change exponentially with a wire that winds up
zig-zag
fashion between two unequal-width spools.
In Excel we modeled the "simple CVT" you suggest and it
is a fairly linear proportion curve. When you overlay
this curve over the exponential torque curve from a
motor, the two do not line up very well.
You're missing that you have a fixed power from the PV
panel. Therefore, the motor has only one operating point.
There is no torque-speed curve; just one operating point
for maximum accelleration.
Now, you could use a PWM controller to vary motor voltage
while maintaining peak power loading of the PV panels. But
I think you will find that this automatically means running
the motor at points away from its peak efficiency.
But, it still might "win" if the extra losses in the
controller and motor were less than losses saved by
replacing the CVT with a fixed or X-speed transmission.
--
"Never doubt that the work of a small group of thoughtful,
committed citizens can change the world. Indeed, it's the
only thing that ever has!" -- Margaret Mead
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377,
leeahart_at_earthlink.net
--- End Message ---
--- Begin Message ---
Found it at http://www.davesevs.com/batteries.htm and its still good.
John
The Skunk http://www.austinev.org/evalbum/preview.php?vid=751
----- Original Message -----
From: "Bob Rice" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Sunday, November 26, 2006 8:37 PM
Subject: Re: Leaking motor, an'Stuff
Hi Storm;
If your worried about a leak, just put a cookie sheet on the carpet
under
the motor<g.>All kidding aside your probably reading through carbon dust
from the brushes? Blow the motor out with compressed air and see if that
makes a differance? Don't breathe that shit, though!Get a cheapo nose air
filter from Tru-Value, or Home Despot. I wouldn't worry about it, if the
damn car RUNS well, be happy!Oh yeah? Are the tops of the batteries clean?
If not hose them clean, dry with the air gun, you ALWAYS unless ya pop for
Optimas or Orbitals ,have the crud, water or damp tops of the floodie
badd-
eries. This is a sloooooow short circuit.Leading to Lee Hart's famous "
Edison Stout, Who Didn't Check His Batteries Out" Poem!There MUST be a
link
for that, plus the In Season "Christmas Story"?
My two ohms worth.
Bob---- Original Message -----
From: "Storm Connors" <[EMAIL PROTECTED]>
To: "List EV" <[email protected]>
Sent: Sunday, November 26, 2006 2:47 PM
Subject: Leaking motor
I am reading 70V between the positive side of my pack and the chassis
ground. If I remove the negative lead to the motor, there is no voltage
between the pack and ground. If I close the contactor which is at the
positive end of the pack, I read 25v from the negative end of the pack to
the chassis and 50v from the positive end of the pack to chassis.
I assume this is a problem. Am I going to have to go inside the motor to
find out what is leaking? FWIW, it seems to be running fine. As a Jeep
owner, I know that is the sure sign of a major problem. Any time it is
running fine, look out.
Thanks,
storm
--
No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.1.409 / Virus Database: 268.14.16/552 - Release Date: 11/26/06
--- End Message ---
--- Begin Message ---
another good source of CVT drives pictures of parts.
they are so cheap when made for mowers. seems that could be a good low
cost source of parts for hobbist car builders.
http://www.jackssmallengines.com/snapperparts_index.html
sorry. this is the correct site
http://www.psep.biz/store/snapper_mower_drive_parts.htm
this parts site has the cvt parts for sale for a snapper riding mower
with pictures.
dirt cheap!
http://images.google.com/imgres?imgurl=http://www.psep.biz/images/mower%2520parts/Snapper%2520Pic%27s/32%252036%2520and%252048%2520walk%2520behind.jpg&imgrefurl=http://www.psep.biz/store/snapper_mower_parts.htm&h=260&w=267&sz=12&hl=en&start=6&tbnid=Fqw0IM9_pphIaM:&tbnh=110&tbnw=113&prev=/images%3Fq%3D%2522snapper%2522%2Bmower%2B%26svnum%3D100%26hl%3Den%26lr%3D%26safe%3Doff%26sa%3DG
Red snapper brand riding mowers used the same kind of drive.
I rode one for years and the thing took hills like a magnatraction car.
they are bullet proof and the rubber discs are so easy to replace IF
they ever wear out.
A simple hand lever slide the wheel on the disc and changed gears . the
lever locked into set notches with a spring for formal "gear" ratios but
it was really infinitely variable.
jerryd wrote:
Hi Tim and All,
The first car to cross the US, The Wilson, had a
CVT made by using a friction wheel against a drive disc,
moving the driven wheel closer and farther from the
centerline to change gears. And it was one of the few things
not to break!!! Using a rollerblade wheel as the drive wheel
and an alum disc, like used for table disc sanders or made
from scratch with a pully and an Alum plate, ect should work
well for your short term needs.
Hope This helps
Jerry Dycus
----- Original Message Follows -----
From: "Offgrid Engineering" <[EMAIL PROTECTED]>
To: "'Lee Hart'" <[EMAIL PROTECTED]>,
<[email protected]>
Subject: RE: Motor selection for 2KW PV solar only drag race
= LONG
Date: Sat, 25 Nov 2006 18:02:49 -0800
Hi Lee:
Sorry I did not give a very complete reply earlier. I'll
try to be more thorough now that I have time. I'll use your
numbers:
1. I totally agree array direct as soon and as long as
possible will be the best course. The car must peak power
trace the array, and "peak efficiency track" the motor to
have max acceleration. And yes it is well understood the
panels peak power and continuous power, unlike batteries,
is the same thing.
2. Yep Vmp = 56V and 35.7 amps
3,4. The CVT is a solution that can keep the motor at the
same RPM, and it is a possible solution here. We have
modeled the CVT using a number of different pulley sizes
and shapes. While we will continue to work on this, we are
a bit dubious that it will be reliable, efficient, give
high repeatability, have an operation curve close to what
we need, be able to be built by high school students. WE
are interested if anyone has built a simple efficient CVT,
and we won't give up developing ours, thanks for the ideas!
I was assuming a buck pwm would be the better choice, and
my calculations given earlier assume that to be the case,
but this may turn out not to be true. The motor needs to
accerate to full rpm in the very beginning, and would you
like to use max array current of about 36 amps or maybe 150
amps, given the same drive ratio? Now one could use a
combination of say DC-DC converter making 12V at 150 amps
to get RPMS up and then switch to a CVT, and we are looking
at that too. But I do believe in KISS.
If a CVT were, used, I agree that the pmdc motor would be
the better choice, for the high efficiency, but if a pwm
controller is used, using the controller as the
transmission, maybe the series motor is not such a bad
choice. Once I get the curves (have an email to ADC) I can
put them in the model to compare to AGNI.
Thanks again...
Tim
-----Original Message-----
From: Lee Hart [mailto:[EMAIL PROTECTED]
Sent: Saturday, November 25, 2006 1:29 AM
To: [email protected]
Subject: Re: Motor selection for 2KW PV solar only drag
race = LONG
Offgrid Engineering wrote:
I think PMDC is a good choice, but a series motor might
be good too
Your solar dragster is a special-case problem, because your
PV panels are the only source of power, and they are a
constant power device. Loading them heavier or lighter than
optimum produces less power, which means you accellerate
slower (and lose the race).
So, you want your motor/controller/transmission to load the
panels at (about) their peak power point throughout the
race, as the car accellerates from 0 to maximum speed.
Here's how I was approaching the problem:
1. The most efficient controller is NONE. A DC motor,
connected
directly to the PV panels. The throttle is just an
"on/off" switch.
2. The peak power point occurs at a particular voltage and
curent.
3. So, the motor will run at a constant voltage and
current. That
implies constant rpm and torque, regardless of vehicle
speed.
4. And that implies a CVT (continuously variable
transmission).
5. Do some calculations using your PV panel's peak power
(2kw?),
motor efficiency at that power (90%?), and the weight of
the
car+driver. Find the resultant wheel rpm vs. time with
this
constant horsepower.
6. Now, using the motor's constant rpm at this power, you
can compute
the CVT ratio as a function of time, to keep the motor
loaded to
its correct speed and torque.
7. Design the pulleys of your CVT to achieve this change in
ratios.
You can have the ratio change linearly by using a flat
band, or
have it change exponentially with a wire that winds up
zig-zag
fashion between two unequal-width spools.
In Excel we modeled the "simple CVT" you suggest and it
is a fairly linear proportion curve. When you overlay
this curve over the exponential torque curve from a
motor, the two do not line up very well.
You're missing that you have a fixed power from the PV
panel. Therefore, the motor has only one operating point.
There is no torque-speed curve; just one operating point
for maximum accelleration.
Now, you could use a PWM controller to vary motor voltage
while maintaining peak power loading of the PV panels. But
I think you will find that this automatically means running
the motor at points away from its peak efficiency.
But, it still might "win" if the extra losses in the
controller and motor were less than losses saved by
replacing the CVT with a fixed or X-speed transmission.
--
"Never doubt that the work of a small group of thoughtful,
committed citizens can change the world. Indeed, it's the
only thing that ever has!" -- Margaret Mead
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377,
leeahart_at_earthlink.net
--- End Message ---
