Electric motor with no tranny for conversion

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Re: Electric motor with no tranny for conversion

Lee Hart
David Dymaxion wrote:
> This is a bit of a nitpick, but you need 1500 ft*lbs to spin the rear
> wheels (2 wheels with 750 lbs each of weight on them), so 965 ft*lbs
> won't quite do it.  It'll still be a fast car and able to climb almost
> any hill you'd see on a U.S. public road.

OK; thanks for the correction. This was just a quick
back-of-the-envelope calculation, so I didn't spend a lot of time
proofreading. :-)

> If you want max acceleration with this setup you'll need either a
> transmission, or more electrical power (maybe even 2 motors), or
> give up some top speed with a lower rear end gear ratio, or a
> lighter car.

Or, a little more controller current (the Zilla actually provides 1000
amps, but I used 900 amps in my estimate because I didn't have the ADC
9" motor's torque at that current). Or, a little higher numerical ratio
for the differential (because my maximum 6000 RPM estimate for the motor
was very conservative).

> This is a fine point primarily of interest to the racers: Weight
> transfer to the rear wheels in a RWD car can significantly raise the
> weight on the rear wheels.

Agreed. This of course works against you for front wheel drive cars (the
most common nowdays).

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in    --    Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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Re: Electric motor with no tranny for conversion

rhgienger
In reply to this post by Richard Marks

If Li-ion with cobalt is considered universally the wrong technology for transportation products, what is the correct choice?
[hidden email]
----------------------------------------

> From: [hidden email]
> To: [hidden email]
> Date: Tue, 27 May 2008 12:20:02 -0400
> Subject: Re: [EVDL] Electric motor with no tranny for conversion
>
> Everybody is interested in seeing Tesla succeed.  The question is, do they
> know enough about automotive test and validation to do it properly.  I  live
> in Detroit and Tesla decided they needed more automotive experience to
> design the roadster and the White/Blue Star future models.  They set up a
> facility here and then laid off half of the people last Fall.  I have spoken
> to several of them, I one thing seems clear.  The Tesla management does not
> understand automotive technology.  The fact that most of management came out
> of software is a real worry.  Software people sell products everyday knowing
> it works most of the time and they can release patches to fix things that
> their customers complain about or sell you new software that fixes the old
> bugs and provide new features.  Great in IT, but that does not work in
> automobiles.  You buy a new car today and do not expect to have any problems
> for 10 years.  Everybody remembers the Bill Gates/Microsoft jokes 10 years
> ago about if MS built cars.  You remember?  Your car would periodically stop
> and you would have to reboot...etc...
> Today's car manufacturers build quality to the tune of 10 defects per
> million parts.  Elon Musk about 2 years ago said if you build electronics
> you don't do it in Detroit, you do it in Silicon Valley.  How little he
> knows.  Today's cars are more complex electrically than any single computer
> that uses PayPal.  And they are extremely reliable!
> My biggest concern is their choice of battery technology. Li-ion with cobalt
> is considered universally the wrong technology for transportation products.
> They probably realize this now, but are they too stubborn to make a change?
> The other issue is life cycle testing.  If a battery is supposed to last 10
> years, how do you get 10 years of testing at a pack level?  You don't.  It
> takes more time and everytime you make an improvement you start the testing
> all over.
> But let's not speculate, time will tell if they can be successful.
>     Richard
> ----- Original Message -----
> From: "Chris Leone"
> To: "Electric Vehicle Discussion List"
> Sent: Sunday, May 25, 2008 6:07 PM
> Subject: Re: [EVDL] Electric motor with no tranny for conversion
>
>
>>>Tesla's mainstream is a two speed transmission. Low gear is for the
>>>breathtaking acceleration and high gear is to get you to 150 mph.  They
>>>have
>>>had problems getting this 2-spd transmission to work and are supposedly
>>>going to build some early models with a single speed and later re-fit
>>>these
>>>with the right transmissions.
>>
>> Actually, the original Tesla founder, Martin Eberhard, wanted to do a
>> single gear ratio, but Elon Musk, the primary VC wanted a two speed to
>> improve the accleration.  The early model cars are actually sent out with
>> the original two speed, locked in 2nd gear and will be retrofitted with a
>> single speed later.  The problem they were having wasn't in house, they
>> assumed, much like the rest of us, that transmissions aren't hard to
>> design.  The problem came when they were looking for a transmission that
>> could handle the low speed torque and the 13,500 rpm redline of their AC
>> motor.  They ran into lubrication issues at these rpms, not torque
>> problems.  So the transmissions were failing due to running without
>> lubrication.  To clarify, Tesla was using an outside transmission designer
>> and didn't think there would be issues.
>>
>>>If Tesla can't do 100 year old technology
>>>right, what makes them think they can do high tech EV technology right?
>>
>> Tesla actually did the EV part very well, their controller for the later
>> model single speed drive train is producing 850 amps at the motor,
>> reaching the goal of sub 4 second 0-60 time, and still pushing over 120
>> mph with a 200+ mile range.  Again, they did not design the transmission,
>> they had left that too the "automotive experts", but that didn't work out.
>> So now they are designing their own.
>>
>>
>> Chris Leone
>> University of Florida
>> Student of Mechanical Engineering
>> 352-278-1176
>>
>>
>>
>> ----- Original Message ----
>> From: Richard Marks
>> To: Electric Vehicle Discussion List
>> Sent: Saturday, May 24, 2008 11:35:51 PM
>> Subject: Re: [EVDL] Electric motor with no tranny for conversion
>>
>>
>>    Rich
>> ----- Original Message -----
>> From: "storm connors"
>> To: "Electric Vehicle Discussion List"
>> Sent: Saturday, May 24, 2008 10:18 PM
>> Subject: Re: [EVDL] Electric motor with no tranny for conversion
>>
>>
>>> Tesla had a 2 speed, didn't it?
>>>
>>> On Sat, May 24, 2008 at 3:20 PM, EVDL Administrator
>>> wrote:
>>>> On 24 May 2008 at 12:26, Lee Hart wrote:
>>>>
>>>>> But essentially *all* EVs designed from scratch have no transmission.
>>>>> The exceptions are the rare ones.
>>>>
>>>> I can think of two more or less recent examples offhand : the Comuta-Van
>>>> and
>>>> the Chrysler TEVan.  The C-van had a 3-speed Borg Warner transmission
>>>> that
>>>> Jim Tervort once told me had originally been designed for a 1930s
>>>> vintage
>>>> Dodge (!).  The Chrysler had a 2-speed gearbox about which I know
>>>> nothing
>>>> more.  Rod Hower had one and was involved in designing the vehicle, so
>>>> he
>>>> might know more details, if you care.
>>>>
>>>> No doubt there are other examples, but my impression is in accord with
>>>> Lee's; most factory EVs (not conversions) in recent years have had
>>>> single
>>>> speed drives.  The obviation of the need for a multispeed transmission
>>>> was
>>>> (and is)  considered a significant advantage of electric motors over
>>>> ICEs.
>>>>
>>>> David Roden - Akron, Ohio, USA
>>>> EVDL Administrator
>>>>
>>>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>>>> EVDL Information: http://www.evdl.org/help/
>>>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>>>> Note: mail sent to "evpost" or "etpost" addresses will not
>>>> reach me.  To send a private message, please obtain my
>>>> email address from the webpage http://www.evdl.org/help/ .
>>>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>>>>
>>>>
>>>> _______________________________________________
>>>> For subscription options, see
>>>> http://lists.sjsu.edu/mailman/listinfo/ev
>>>>
>>>
>>>
>>>
>>> --
>>> http://www.austinev.org/evalbum/1059
>>> http://stormselectric.blogspot.com/
>>> Storm
>>>
>>> _______________________________________________
>>> For subscription options, see
>>> http://lists.sjsu.edu/mailman/listinfo/ev
>>>
>>
>> _______________________________________________
>> For subscription options, see
>> http://lists.sjsu.edu/mailman/listinfo/ev
>> _______________________________________________
>> For subscription options, see
>> http://lists.sjsu.edu/mailman/listinfo/ev
>>
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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Re: Electric motor with no tranny for conversion

Roger Stockton
In reply to this post by Lee Hart
Lee Hart wrote:

> Or, a little higher numerical ratio for the
> differential (because my maximum 6000 RPM estimate for the
> motor was very conservative).

I hope you're right about that ;^>

Jim Husted has strongly cautioned against operating either the ADC or Warp 9"ers at 6600RPM even briefly based on what he knows of their comms and the 'sploded ones he's seen.

Even Rudman says he limits his 8" to 5500 on the street and 6500 for racing...

Not that you are likely to get anywhere near that running a 132V pack of floodies unless you spin a wheel ;^>

Cheers,

Roger.

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Re: Electric motor with no tranny for conversion

Jeff Shanab
In reply to this post by chazersize
David, I was gonna say a similar thing about weight transfer.  we can
also look at it from the G force side of things

But we must graph it because as soon as we achieve motion the
acceleration rate drops.
  I think if we were to plot drag racing EV's AC against DC against ICE
we will see a patern
    AC accelrates slower but accross a wider speed range,   a multispeed
tranny not as important
    DC accelrates best off the line droping as speed increases a
multispeed tranny could be of help here
    ICE accelerates in relation to engine rpm and peaks 30 ft out of the
gate and has a secondary peak again in next gear. a multispeed tranny is
imperative.

 .25G acceleration is minimally acceptable
 Most passenger cars can generate launch of .5  and braking of .7
 Most trucks and SUV's are all over the map. they have both way worse
and way more than passenger cars.
 Most sports cars can generate launch of .7-.9 and braking of .9G and
also can have lateral G's of close to 1.0G
 
 750/3000 = .25G, this is anemic. Most drivers will feel this and complain.
1500/300 = .5G This is spirited, People will say wow at first. You can
sell this easy.

I played with this

This graph is generated by php code that pits all the specs I could find
for the white zombie and gone postal in a virtual drag race.
   http://cvevs.jfs-tech.com/graph3.php

Here is the source code of that php (you can run php locally). You can
see the equations in it, they came from a book on race design.

   http://cvevs.jfs-tech.com/graph3.txt

   This program handles weight transfer to determine max adhesion and
values for spring rates, throttle response, shift times had to all be
guessed. The stages are series parallel or gear shifts and it allows for
multiple axles. This was done long before the white zombie broke the
100mph 12.9 sec and you can see it is way off. To many variables guessed
I think.




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Re: Electric motor with no tranny for conversion

Jeff Shanab
In reply to this post by chazersize
David, I was gonna say a similar thing about weight transfer.  we can
also look at it from the G force side of things

But we must graph it because as soon as we achieve motion the
acceleration rate drops.
  I think if we were to plot drag racing EV's AC against DC against ICE
we will see a patern
    AC accelrates slower but accross a wider speed range,   a multispeed
tranny not as important
    DC accelrates best off the line droping as speed increases a
multispeed tranny could be of help here
    ICE accelerates in relation to engine rpm and peaks 30 ft out of the
gate and has a secondary peak again in next gear. a multispeed tranny is
imperative.

 .25G acceleration is minimally acceptable
 Most passenger cars can generate launch of .5  and braking of .7
 Most trucks and SUV's are all over the map. they have both way worse
and way more than passenger cars.
 Most sports cars can generate launch of .7-.9 and braking of .9G and
also can have lateral G's of close to 1.0G

 750/3000 = .25G, this is anemic. Most drivers will feel this and complain.
1500/300 = .5G This is spirited, People will say wow at first. You can
sell this easy.

I played with this

This graph is generated by php code that pits all the specs I could find
for the white zombie and gone postal in a virtual drag race.
   http://cvevs.jfs-tech.com/graph3.php

Here is the source code of that php (you can run php locally). You can
see the equations in it, they came from a book on race design.

   http://cvevs.jfs-tech.com/graph3.txt

   This program handles weight transfer to determine max adhesion and
values for spring rates, throttle response, shift times had to all be
guessed. The stages are series parallel or gear shifts and it allows for
multiple axles. This was done long before the white zombie broke the
100mph 12.9 sec and you can see it is way off. To many variables guessed
I think.





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Re: Electric motor with no tranny for conversion

Lee Hart
In reply to this post by Jeff Shanab
Jeff Shanab wrote:
>   I think if we were to plot drag racing EVs AC against DC against ICE
> we will see a pattern... AC accelerates slower but across a wider speed
> range. A multispeed tranny is not as important.

This point is really a consequence of a high battery voltage vs. low
battery voltage (compared to motor voltage).

Suppose you have a 120v motor and a 120v pack. The controller is in
current limit (say, 500 amps) until the motor reaches 120v. 120v at 500
amps is a relatively low RPM; depending on gearing, it might be 30 mph.
Constant current means constant torque, so you get roughly constant
acceleration up to 30 mph. Above this, the controller comes out of
current limit, so torque and acceleration drop.

If instead you have a 120v motor and a 240v pack, the controller stays
in current limit until the motor reaches 240v. Now you have constant
acceleration up to 60 mph.

Almost all the AC EVs run 300v packs (or thereabouts). Almost all DC EVs
run pack voltage of about half this. It's not a requirement, as there
are exceptions on both sides. It's just a consequence of using the
available hardware.

> .25G acceleration is minimally acceptable... 750/3000 = .25G, this is
> anemic. Most drivers will feel this and complain. 1500/3000 = .5G...
> This is spirited, people will say wow at first. You can sell this easy.

The 750 lbs thrust on a 3000 lbs vehicle in my quickie example was an
error; that's what you get for 10 minutes of free engineering. :-) I
should have doubled it, as you have two tires delivering 750 lbs each.

You also need more power from the motor and controller. I used a Z1K
delivering 900a with a 4.29:1 differential in the example. In our
Sunrise, we're actually using a Z2K controller and 5:1 differential.

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in    --    Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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Re: Electric motor with no tranny for conversion

Richard Marks
In reply to this post by Neon John
Neon,
    The number I saw that Tesla has raised was $145M as reported in LA
Times!  I have a company in Detroit that is ready to start producing an
electric Low Speed Vehicle and I can't even raise a dime!  visit me at
www.EcoVElectric.com
Richard
----- Original Message -----
From: "Neon John" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Tuesday, May 27, 2008 3:58 PM
Subject: Re: [EVDL] Electric motor with no tranny for conversion


> On Tue, 27 May 2008 12:20:02 -0400, "Richard Marks"
> <[hidden email]>
> wrote:
>
>
>>Today's car manufacturers build quality to the tune of 10 defects per
>>million parts.  Elon Musk about 2 years ago said if you build electronics
>>you don't do it in Detroit, you do it in Silicon Valley.  How little he
>>knows.  Today's cars are more complex electrically than any single
>>computer
>>that uses PayPal.  And they are extremely reliable!
>
> Yep.  Automotive electronics are on par with and in some cases better than
> aerospace.  All quietly done by the companies that so many on this list
> love
> to hate.
>
>>My biggest concern is their choice of battery technology. Li-ion with
>>cobalt
>>is considered universally the wrong technology for transportation
>>products.
>>They probably realize this now, but are they too stubborn to make a
>>change?
>>The other issue is life cycle testing.  If a battery is supposed to last
>>10
>>years, how do you get 10 years of testing at a pack level?  You don't.  It
>>takes more time and everytime you make an improvement you start the
>>testing
>>all over.
>
> All true.  I just marvel that an outfit like that can run through over $25
> million dollars and have practically nothing to show for it.  The car
> itself
> is built for them by Lotus.  The drive system is AC Propulsion.  I'm not
> sure
> just what it is they've spent all that money on.  My mind races at the
> thought
> of what I could do in the EV world with a tenth that much money.
>
>>But let's not speculate, time will tell if they can be successful.
>
> Here's a good place to keep track.
>
> http://www.thetruthaboutcars.com/category/news-blog/tesla-death-watch/
>
> This is some pretty good reporting by folks who haven't drank the Kool-Aid
> on
> Tesla's activities up to allegedly delivering the first "production" (sic)
> car
>
> http://www.thetruthaboutcars.com/category/news-blog/tesla-birth-watch/
>
> Note the next to last entry where they report on Larry Sonsini, the
> scandalous
> M&A shark, joining the board.  Sounds like the "dump" part of
> "pump'n'dump" is
> being planned for.
>
> John
> --
> John De Armond
> See my website for my current email address
> http://www.neon-john.com
> http://www.johndearmond.com <-- best little blog on the net!
> Tellico Plains, Occupied TN
> If the letters PhD appear after a person's name, that person will
> remain outdoors even after it's started raining.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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Re: Electric motor with no tranny for conversion

Richard Marks
In reply to this post by rhgienger
The world is following iron phosphate (A123) or manganese spinel (EnerDel).
Some of the manganese batteries are showing energy storage much better than
the cobalts and are very robust from an abuse standpoint.
Richard
----- Original Message -----
From: "Robert Gienger" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Wednesday, May 28, 2008 12:24 AM
Subject: Re: [EVDL] Electric motor with no tranny for conversion



If Li-ion with cobalt is considered universally the wrong technology for
transportation products, what is the correct choice?
[hidden email]
----------------------------------------

> From: [hidden email]
> To: [hidden email]
> Date: Tue, 27 May 2008 12:20:02 -0400
> Subject: Re: [EVDL] Electric motor with no tranny for conversion
>
> Everybody is interested in seeing Tesla succeed.  The question is, do they
> know enough about automotive test and validation to do it properly.  I
> live
> in Detroit and Tesla decided they needed more automotive experience to
> design the roadster and the White/Blue Star future models.  They set up a
> facility here and then laid off half of the people last Fall.  I have
> spoken
> to several of them, I one thing seems clear.  The Tesla management does
> not
> understand automotive technology.  The fact that most of management came
> out
> of software is a real worry.  Software people sell products everyday
> knowing
> it works most of the time and they can release patches to fix things that
> their customers complain about or sell you new software that fixes the old
> bugs and provide new features.  Great in IT, but that does not work in
> automobiles.  You buy a new car today and do not expect to have any
> problems
> for 10 years.  Everybody remembers the Bill Gates/Microsoft jokes 10 years
> ago about if MS built cars.  You remember?  Your car would periodically
> stop
> and you would have to reboot...etc...
> Today's car manufacturers build quality to the tune of 10 defects per
> million parts.  Elon Musk about 2 years ago said if you build electronics
> you don't do it in Detroit, you do it in Silicon Valley.  How little he
> knows.  Today's cars are more complex electrically than any single
> computer
> that uses PayPal.  And they are extremely reliable!
> My biggest concern is their choice of battery technology. Li-ion with
> cobalt
> is considered universally the wrong technology for transportation
> products.
> They probably realize this now, but are they too stubborn to make a
> change?
> The other issue is life cycle testing.  If a battery is supposed to last
> 10
> years, how do you get 10 years of testing at a pack level?  You don't.  It
> takes more time and everytime you make an improvement you start the
> testing
> all over.
> But let's not speculate, time will tell if they can be successful.
>     Richard
> ----- Original Message -----
> From: "Chris Leone"
> To: "Electric Vehicle Discussion List"
> Sent: Sunday, May 25, 2008 6:07 PM
> Subject: Re: [EVDL] Electric motor with no tranny for conversion
>
>
>>>Tesla's mainstream is a two speed transmission. Low gear is for the
>>>breathtaking acceleration and high gear is to get you to 150 mph.  They
>>>have
>>>had problems getting this 2-spd transmission to work and are supposedly
>>>going to build some early models with a single speed and later re-fit
>>>these
>>>with the right transmissions.
>>
>> Actually, the original Tesla founder, Martin Eberhard, wanted to do a
>> single gear ratio, but Elon Musk, the primary VC wanted a two speed to
>> improve the accleration.  The early model cars are actually sent out with
>> the original two speed, locked in 2nd gear and will be retrofitted with a
>> single speed later.  The problem they were having wasn't in house, they
>> assumed, much like the rest of us, that transmissions aren't hard to
>> design.  The problem came when they were looking for a transmission that
>> could handle the low speed torque and the 13,500 rpm redline of their AC
>> motor.  They ran into lubrication issues at these rpms, not torque
>> problems.  So the transmissions were failing due to running without
>> lubrication.  To clarify, Tesla was using an outside transmission
>> designer
>> and didn't think there would be issues.
>>
>>>If Tesla can't do 100 year old technology
>>>right, what makes them think they can do high tech EV technology right?
>>
>> Tesla actually did the EV part very well, their controller for the later
>> model single speed drive train is producing 850 amps at the motor,
>> reaching the goal of sub 4 second 0-60 time, and still pushing over 120
>> mph with a 200+ mile range.  Again, they did not design the transmission,
>> they had left that too the "automotive experts", but that didn't work
>> out.
>> So now they are designing their own.
>>
>>
>> Chris Leone
>> University of Florida
>> Student of Mechanical Engineering
>> 352-278-1176
>>
>>
>>
>> ----- Original Message ----
>> From: Richard Marks
>> To: Electric Vehicle Discussion List
>> Sent: Saturday, May 24, 2008 11:35:51 PM
>> Subject: Re: [EVDL] Electric motor with no tranny for conversion
>>
>>
>>    Rich
>> ----- Original Message -----
>> From: "storm connors"
>> To: "Electric Vehicle Discussion List"
>> Sent: Saturday, May 24, 2008 10:18 PM
>> Subject: Re: [EVDL] Electric motor with no tranny for conversion
>>
>>
>>> Tesla had a 2 speed, didn't it?
>>>
>>> On Sat, May 24, 2008 at 3:20 PM, EVDL Administrator
>>> wrote:
>>>> On 24 May 2008 at 12:26, Lee Hart wrote:
>>>>
>>>>> But essentially *all* EVs designed from scratch have no transmission.
>>>>> The exceptions are the rare ones.
>>>>
>>>> I can think of two more or less recent examples offhand : the
>>>> Comuta-Van
>>>> and
>>>> the Chrysler TEVan.  The C-van had a 3-speed Borg Warner transmission
>>>> that
>>>> Jim Tervort once told me had originally been designed for a 1930s
>>>> vintage
>>>> Dodge (!).  The Chrysler had a 2-speed gearbox about which I know
>>>> nothing
>>>> more.  Rod Hower had one and was involved in designing the vehicle, so
>>>> he
>>>> might know more details, if you care.
>>>>
>>>> No doubt there are other examples, but my impression is in accord with
>>>> Lee's; most factory EVs (not conversions) in recent years have had
>>>> single
>>>> speed drives.  The obviation of the need for a multispeed transmission
>>>> was
>>>> (and is)  considered a significant advantage of electric motors over
>>>> ICEs.
>>>>
>>>> David Roden - Akron, Ohio, USA
>>>> EVDL Administrator
>>>>
>>>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>>>> EVDL Information: http://www.evdl.org/help/
>>>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>>>> Note: mail sent to "evpost" or "etpost" addresses will not
>>>> reach me.  To send a private message, please obtain my
>>>> email address from the webpage http://www.evdl.org/help/ .
>>>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>>>>
>>>>
>>>> _______________________________________________
>>>> For subscription options, see
>>>> http://lists.sjsu.edu/mailman/listinfo/ev
>>>>
>>>
>>>
>>>
>>> --
>>> http://www.austinev.org/evalbum/1059
>>> http://stormselectric.blogspot.com/
>>> Storm
>>>
>>> _______________________________________________
>>> For subscription options, see
>>> http://lists.sjsu.edu/mailman/listinfo/ev
>>>
>>
>> _______________________________________________
>> For subscription options, see
>> http://lists.sjsu.edu/mailman/listinfo/ev
>> _______________________________________________
>> For subscription options, see
>> http://lists.sjsu.edu/mailman/listinfo/ev
>>
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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Re: Electric motor with no tranny for conversion

Jeff Shanab
In reply to this post by chazersize
> Jeff Shanab wrote:
>>   I think if we were to plot drag racing EVs AC against DC against ICE
>> we will see a pattern... AC accelerates slower but across a wider speed
>> range. A multispeed tranny is not as important.
>
> This point is really a consequence of a high battery voltage vs. low
> battery voltage (compared to motor voltage).
>
> Suppose you have a 120v motor and a 120v pack. The controller is in
> current limit (say, 500 amps) until the motor reaches 120v. 120v at
> 500 amps is a relatively low RPM; depending on gearing, it might be 30
> mph. Constant current means constant torque, so you get roughly
> constant acceleration up to 30 mph. Above this, the controller comes
> out of current limit, so torque and acceleration drop.
>
> If instead you have a 120v motor and a 240v pack, the controller stays
> in current limit until the motor reaches 240v. Now you have constant
> acceleration up to 60 mph.
>
> Almost all the AC EVs run 300v packs (or thereabouts). Almost all DC
> EVs run pack voltage of about half this. It's not a requirement, as
> there are exceptions on both sides. It's just a consequence of using
> the available hardware.

I think that is why i was saying "see a pattern" As you have said in the
past, most of this is mostly because of tradition anyway.  I think a
wound rotor AC motor could be built that would rival the series DC for
torque off the line and then deliver more across a broader range. It is
one of the few motor topologies that is built for more than one rpm.

>
>> .25G acceleration is minimally acceptable... 750/3000 = .25G, this is
>> anemic. Most drivers will feel this and complain. 1500/3000 = .5G...
>> This is spirited, people will say wow at first. You can sell this easy.
>
> The 750 lbs thrust on a 3000 lbs vehicle in my quickie example was an
> error; that's what you get for 10 minutes of free engineering. :-) I
> should have doubled it, as you have two tires delivering 750 lbs each.
>
> You also need more power from the motor and controller. I used a Z1K
> delivering 900a with a 4.29:1 differential in the example. In our
> Sunrise, we're actually using a Z2K controller and 5:1 differential.
OMG that think is gonna smoke!
Is there room to get a dual motor set up in there? I would like to try
S/P off of a z1k next.

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Re: Electric motor with no tranny for conversion

Jeff Shanab
In reply to this post by chazersize
Someone said something about open vs posi rear ends that I think was
missleading.

Open rear ends allow transfering the most power to the ground on
straight-aways and in corners. With the proviso that the wheels stay in
contact with the road. Some road racers take this approach: go open and
soften the suspension to allow the wheel to remain in contact at all
times. This appears to work better on stock vehicles where the roll
center is high.

One of those "in theory theory is easier than practice, in practice...."
situations, but I can tell you that going from open to 140Lb preloaded
limited slip required a lot of changes to get back lost turn in in a n
autocross, Other locking diffys that don't have that drag are far better.

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Re: Electric motor with no tranny for conversion

Peter VanDerWal
Yes, it seems there is a common misconception that open diffs only power
one wheel.
It is true that, with an open diff, if one wheel looses traction and
begins to slip, all you power goes to that wheel.
However, unless one wheel is slipping, the torque splits between the
wheels in nearly equal amounts.

> Someone said something about open vs posi rear ends that I think was
> missleading.
>
> Open rear ends allow transfering the most power to the ground on
> straight-aways and in corners. With the proviso that the wheels stay in
> contact with the road. Some road racers take this approach: go open and
> soften the suspension to allow the wheel to remain in contact at all
> times. This appears to work better on stock vehicles where the roll
> center is high.
>
> One of those "in theory theory is easier than practice, in practice...."
> situations, but I can tell you that going from open to 140Lb preloaded
> limited slip required a lot of changes to get back lost turn in in a n
> autocross, Other locking diffys that don't have that drag are far better.
>
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Re: Electric motor with no tranny for conversion

Mark Grasser
> Yes, it seems there is a common misconception that open diffs only power
> one wheel.

Really, There are people that think that the power goes to only one wheel?

> It is true that, with an open diff, if one wheel looses traction and
> begins to slip, all you power goes to that wheel.

Exactly what I meant when I made the argument about open differential. In
rear wheel drive vehicles using an open drive shaft the torque applied to
the driveshaft tends to lift one side of the axle, the side that is first to
spin.

> However, unless one wheel is slipping, the torque splits between the
> wheels in nearly equal amounts.


Mark Grasser
Eliot, ME

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Re: Electric motor with no tranny for conversion

AMPrentice
In reply to this post by storm connors
Does anyone know which transmission Tesla decided to use?
I thought they would have used a Lenco, liberty or others readily available
for high rpm speedway engines.

storm connors wrote
Tesla had a 2 speed, didn't it?

On Sat, May 24, 2008 at 3:20 PM, EVDL Administrator <evpost@drmm.net> wrote:
> On 24 May 2008 at 12:26, Lee Hart wrote:
>
>> But essentially *all* EVs designed from scratch have no transmission.
>> The exceptions are the rare ones.
>
> I can think of two more or less recent examples offhand : the Comuta-Van and
> the Chrysler TEVan.  The C-van had a 3-speed Borg Warner transmission that
> Jim Tervort once told me had originally been designed for a 1930s vintage
> Dodge (!).  The Chrysler had a 2-speed gearbox about which I know nothing
> more.  Rod Hower had one and was involved in designing the vehicle, so he
> might know more details, if you care.
>
> No doubt there are other examples, but my impression is in accord with
> Lee's; most factory EVs (not conversions) in recent years have had single
> speed drives.  The obviation of the need for a multispeed transmission was
> (and is)  considered a significant advantage of electric motors over ICEs.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
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Storm

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