# [EVDL] design input?



## EVDL List (Jul 27, 2007)

Price is third eh : ) sounds expensive
not sure why you think AC is better for direct drive than DC. direct 
drive is very high gearing so requires great torque.
with acceleration as your primary concern I'd say you should look at the 
white zombie and killacycle configuration. and lead is probably the 
simplest like white zombie did. you can use lithiums for that extra 
performance and weight elegance but added complexity from assembling the 
many cells and finding bms.
lead acid white zombie seems to be very close to what you are describing.
although I'm not sure I'd go direct drive if the resulting gearing is 
only 1:4. it would be like starting in 4th or 5th gear.
does WZ use a diff with higher ratio?

as for ACpropulsion, money better be a really distant 3rd because he 
wants 25k$ for that. and it probably wouldn't beat white zombie anyway.
I am not omniscient about available AC controller products but it's my 
impression that there aren't any with really high power and those there 
are are expensive. motors too

Dan





> Mark Maher wrote:
> > Hi all... very new subscriber here, so if you have any posting
> > recommendations, please let me know.
> >
> ...


----------



## EVDL List (Jul 27, 2007)

> Mark Maher wrote:
> > Anyway, I'd like to convert a vehicle for performance first, range
> > secondary, and price third. I'm thinking of doing a 2000 or 2001 Subaru
> > Impreza.
> ...


----------



## EVDL List (Jul 27, 2007)

Hmm, most of the AC motors currently available will need at least a 10:1
reduction for direct drive. The axle gives you ~ 4:1 so how are you going
to make up the difference without a transmission?

> Hi all... very new subscriber here, so if you have any posting
> recommendations, please let me know.
>
> Anyway, I'd like to convert a vehicle for performance first, range
> secondary, and price third. I'm thinking of doing a 2000 or 2001 Subaru
> Impreza. My idea is to ditch the AWD and just go AC, direct, rear drive
> only. I think this could result in lower weight, lower center of gravity
> (motor could go where the tranny normally does and leave tons of room for
> batteries and controller up front with some more battery space in a rear
> box
> if desired) and for just general simplicity. An alternative would be to
> use
> a big DC motor on the existing AWD drivetrain. 2 axle ratios were offered
> in this chassis 3.90:1 and 4:10:1. Probably start with AGM batteries and
> maybe move to more exotic on down the line??
>
> I guess my main concern at this point is regarding motor choice. I know
> this has been hotly contested on more than one occasion, but in this case
> the difference could mean a whole different drivetrain configuration and
> I'd
> like to get some input from the community.
>
> An AC motor seems suited for the rpm range required for direct drive (top
> speed max of ~90 mph would be fine) and for native regen to help in the
> range department, but would it have enough torque to be entertaining at
> stoplights, climb hills, etc? I'd like to be able to break the tires
> loose
> from a start and generally tear around.
>
> Anyone have experience with the Siemens motors / controllers like from
> metricmind.com or possibly the AC Propulsion (pipedream) AC150? DC seems
> to
> win the battle on sheer torque (generalizing) but would it be worth the
> packaging and weight handicap in addition to the lack of regen? Also, if
> I'm ditching the tranny via AC direct drive it might make it easier to
> find
> a donor vehicle as auto/manual doesn't matter...
>
> Regards,
> Mark
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>


-- 
If you send email to me, or the EVDL, that has > 4 lines of legalistic
junk at the end; then you are specifically authorizing me to do whatever I
wish with the message. By posting the message you agree that your long
legalistic signature is void.

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Thanks for the replies....

I thought AC motors went to 8-12k for top rpm whereas DC was about half that
(looking at overall freeway-ability). Seems like I'd need still more
reduction than I can get in a diff, though. I'd seen the White Zombie page
early on in my investigations. I'll go back and have a closer look. I
think I had moved on mentally because I assumed that the drag racers were so
specialized that range was not realistic for around town.

- Mark



> Dan Frederiksen <[email protected]> wrote:
> 
> > Price is third eh : ) sounds expensive
> > not sure why you think AC is better for direct drive than DC. direct
> ...


----------



## EVDL List (Jul 27, 2007)

Yeah... I saw those guys, which sort of started me down the thought
process. I'll see if I can send them a pm via there website.



> Tom Parker <[email protected]> wrote:
> 
> > On Mon, 2007-12-03 at 00:12 -1000, Mark Maher wrote:
> > > Anyway, I'd like to convert a vehicle for performance first, range
> ...


----------



## EVDL List (Jul 27, 2007)

Right. I've been wondering over the parameters involved in final drive
decision. All the motors on EVparts.com are DC and I haven't found any AC
torque curves. If a 10:1 is needed (is this specified?) then that may throw
a monkey wrench into the driveshaft-off-the-motor idea. I guess a
transmission would be needed afterall, in which case I could just do DC and
keep the original drivetrain and get reverse plus multiple ratios.

Anyone ever tried an automatic minus the torque converter? I know a lot of
ICE drag racers use 2 speed Powerglide trannies for their durability. If
one could ditch the bellhousing or make a flat plate one for packaging maybe
that could work since shifting under power may not be necessary?

- Mark



> Peter VanDerWal <[email protected]> wrote:
> 
> > Hmm, most of the AC motors currently available will need at least a 10:1
> > reduction for direct drive. The axle gives you ~ 4:1 so how are you going
> ...


----------



## EVDL List (Jul 27, 2007)

Yes AC tends to have a significant advantage in the rpm range (no 
mechanical commutators, hmm got an idea..) but that's an advantage in 
power density that you can only capitalize on when you exceed the rpm 
the DC motor can't do. you are quite right that you could get away with 
a fixed gear with an AC drive but it would need a greater gear ratio 
than the typical car differrential will give you (1:3-1:4). something 
like 1:10 might be a good fixed point.

I don't have much experience with automechanics but maybe a 1:10 diff 
could be found? maybe some light construction vehicle that is slow but 
strong would have such a diff.
that's more or less what tesla is doing. they only have 2 gears.

that said though, while electric drive does have high torque across the 
rpm range, its maximum power (that which pays for your acceleration) is 
in the high rpm of the motor so if you can switch gears fast enough, 
more gears generally help apply more power (keep it in the high rpm). on 
the other hand, the weight spent on a gearbox could be spent on more motor..
many little competing parameters

Dan




> Mark Maher wrote:
> > Thanks for the replies....
> >
> > I thought AC motors went to 8-12k for top rpm whereas DC was about half that
> ...


----------



## EVDL List (Jul 27, 2007)

What if you used the front wheel drive subaru transmission from an EA
series or early legacy and just removed the driveshaft, rear diff, and
rear axles of the imp (except for the stub shafts). Then you still
have the advantage of having the transmission, so you could use
smaller DC motor instead of direct driving the rear differential, but
you don't have the added drag of an AWD setup.

Z



> Mark Maher <[email protected]> wrote:
> > Right. I've been wondering over the parameters involved in final drive
> > decision. All the motors on EVparts.com are DC and I haven't found any AC
> > torque curves. If a 10:1 is needed (is this specified?) then that may throw
> ...


----------



## EVDL List (Jul 27, 2007)

That's a pretty good idea, although the idea of doing a Subaru was mainly to
facilitate a smallish fairly modern (wife mandates airbags) 4 door on a rear
drive platform. This is tricky (without price prohibitive fab work) as
most are all FWD. I think if I went front drive I'd probably choose a
different donor. Maybe a late Integra sedan (still haven't bought the donor
yet, just brainstorming). I do like Subaru's though, this will/would be my
fifth. Thanks for the reply.

On 12/3/07, Zeke Yewdall <[email protected]> wrote:
>
> What if you used the front wheel drive subaru transmission from an EA
> series or early legacy and just removed the driveshaft, rear diff, and
> rear axles of the imp (except for the stub shafts). Then you still
> have the advantage of having the transmission, so you could use
> smaller DC motor instead of direct driving the rear differential, but
> you don't have the added drag of an AWD setup.
>
> Z
>
>


> Mark Maher <[email protected]> wrote:
> > > Right. I've been wondering over the parameters involved in final drive
> > > decision. All the motors on EVparts.com are DC and I haven't found any
> > AC
> ...


----------



## EVDL List (Jul 27, 2007)

As an example at the other end of the spectrum:
My US Electricar S10 (converted chevy truck) has an
AC motor with 9,000 RPM redline directly attached to
the original manual gearbox which has no shifter, but
instead if locked in second gear to provide the
necessary reduction and the rest of the drivetrain
(shaft to rear axle, diff, wheels) is unaltered.
With the standard 2nd gear, the 9,000 RPM redline
is reached at 72 MPH. In fact, converting RPM to MPH
is easy: 125 RPM per MPH; 1,000 each 8 MPH.

NOTE that the absence of low gear and the low current
limit on my controller (250A to the motor, 200A from
the battery at 312V pack voltage) makes for a less
than impressive launch speed, but if the need to drive
electric is not accompanied by the *wish* to take off
fast, then the glacial pace of a totally silent car
can be more impressive than burning rubber.


Cor van de Water
Systems Architect
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
Fax: +1 408 731 3675 eFAX: +31-87-784-1130
Second Life: www.secondlife.com/?u=3b42cb3f4ae249319edb487991c30acb

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Mark Maher
Sent: Monday, December 03, 2007 8:42 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] design input?

Thanks for the replies....

I thought AC motors went to 8-12k for top rpm whereas DC was about half that (looking at overall freeway-ability). Seems like I'd need still more reduction than I can get in a diff, though. I'd seen the White Zombie page early on in my investigations. I'll go back and have a closer look. I think I had moved on mentally because I assumed that the drag racers were so specialized that range was not realistic for around town.

- Mark



> Dan Frederiksen <[email protected]> wrote:
> 
> > Price is third eh : ) sounds expensive not sure why you think AC is
> > better for direct drive than DC. direct drive is very high gearing so
> ...


----------



## EVDL List (Jul 27, 2007)

Actually, from what I hear, the White Zombie gets about 40 miles range
around town.

> I'd seen the White Zombie page early on in my investigations. I'll go back and have a closer look. I think I had moved on mentally > because I assumed that the drag racers were so specialized that range was not realistic for around town.
>
> - Mark
>

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

In EV sized motors, high rpm needs high frequency, high frequency needs
special materials.

rpm = [freq(cycles/sec) * 60(seconds/min)]/(pole pairs) - slip so (60
* 60) / 2 (4 pole = 2 pole pair) == 3600/2 = 1800 rpm * .958 = 1725rpm

same motor on 50hz = 1437rpm
same motor at 400hz = 12,000 rpm

The losses in a 60hz motor pushed to 400hz would be horrendous. 120hz is
about the limit.


_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

> Anyone ever tried an automatic minus the torque converter? =

Many automatic trannys use vaccume to measure when to shift. The other prob=
lem is they need an idling engine to keep pumps going etc. Otherwise you ca=
n't instantly take off and also something lubricated may go too dry.
=

Of course you could simulate the vac-input and have an idle position for th=
e motor, but then you need the clutch to be able to stand still. Guess you =
could shift to nutral though. Vaccume sensors can be reprogrammed or replac=
ed, but the contiuous pumping? Seems counter productive.



Arak Leatham - Web and Desktop Systems Developer




Estimating, Point of Sale, Tracking, Reporting Applications> Date: Mon, 3 D=
ec 2007 07:00:35 -1000> From: [email protected]> To: [email protected]; [email protected]=
lists.sjsu.edu> Subject: Re: [EVDL] design input?> > Right. I've been wonde=
ring over the parameters involved in final drive> decision. All the motors =
on EVparts.com are DC and I haven't found any AC> torque curves. If a 10:1 =
is needed (is this specified?) then that may throw> a monkey wrench into th=
e driveshaft-off-the-motor idea. I guess a> transmission would be needed af=
terall, in which case I could just do DC and> keep the original drivetrain =
and get reverse plus multiple ratios.> > Anyone ever tried an automatic min=
us the torque converter? I know a lot of> ICE drag racers use 2 speed Power=
glide trannies for their durability. If> one could ditch the bellhousing or=
make a flat plate one for packaging maybe> that could work since shifting =
under power may not be necessary?> > - Mark> > On Dec 3, 2007 6:35 AM, Pete=


> r VanDerWal <[email protected]> wrote:> > > Hmm, most of the AC motors curr=
> ently available will need at least a 10:1> > reduction for direct drive. Th=
> e axle gives you ~ 4:1 so how are you going> > to make up the difference wi=
> thout a transmission?> >> > > Hi all... very new subscriber here, so if you=
> ...


----------



## EVDL List (Jul 27, 2007)

I've never understood the attraction of rear wheel drive... but what
if you put a front wheel drive transmission in the back of a car, and
reversed the direction of motor rotation so the car still went
forwards. That would essentially be the same as direct driving the
rear differential, but with the benefit of a transmission... even if
you did something like lock it in 2nd gear or something. Sort of like
the VW bugs.

Another idea... a typical 4wd transfer case is about 2:1 ratio....
what if you got a divorced T-case and fed the motor into it, then
drove the driveshaft from the output. Not sure how the losses of this
and weight would compare to a transaxle. You'd also have to get a
transfer case that could stand the RPM

Or, use a part time 4wd subaru transmission, and take the front axle
shafts out, with it in 4wd. They seem to be be strong enough to stand
this for a while, depending on how much torque you are transmitting.
The 4 wheelers who install a divorced transfer case and solid front
axle on subaru's do this. Actually, if you are going to a rear wheel
drive setup, you could use something like a 2wd S-10 transmission,
with easily available motor adaptors, and then just fabricate customer
motor/transmission mounts, and a custom driveshaft....

Hmmmmm....



> Mark Maher <[email protected]> wrote:
> > That's a pretty good idea, although the idea of doing a Subaru was mainly to
> > facilitate a smallish fairly modern (wife mandates airbags) 4 door on a rear
> > drive platform. This is tricky (without price prohibitive fab work) as
> ...


----------



## EVDL List (Jul 27, 2007)

Hello to Zeke and All,



> Zeke Yewdall wrote:
> 
> >I've never understood the attraction of rear wheel drive...
> >
> ...


----------



## EVDL List (Jul 27, 2007)

Ah yes, how could I forget that.... I've never owned any vehicle
with enough horsepower to matter -- 70 some HP just doesn't do it....
 Actually, come to think of it, my EV is going to the most
powerful vehicle I own when I get it done, at least in terms of peak
power.

Z



> John Wayland <[email protected]> wrote:
> > Hello to Zeke and All,
> >
> > Zeke Yewdall wrote:
> ...


----------



## EVDL List (Jul 27, 2007)

> > Wayland wrote:
> > Look at the photo here to understand:
> >
> > http://www.plasmaboyracing.com/reviews.php#2007e
> ...


----------



## EVDL List (Jul 27, 2007)

Thanks for the vote of confidence John. Also for handling sake the front
tires tend to get "busy" doing the turning and the lion's share of stopping,
adding acceleration to the mix can be overwhelming. Not to mention weight
transfers onto the driving wheels instead of away during acceleration.
Anyway... it seems that using an existing transmission is the more
sensible/flexible option. Then if I go DC for a lot of lowdown torque I can
have various ranges available and mechanical reverse. Plus keeping AWD
would be fun for putting down the power efficiently. I'm not going to say
(now) that drag racing is my main interest. Primarily just want to make a
sleeper EV for my own entertainment and also maybe open some friends eyes
about electric.

Since I'm clearly such a noob, can anyone recommend some threads concerning
the advantages of dual motors v. one bigger motor and how the whole
serial/parallel switching works? This stuff isn't exactly on Ask.com and I'm
having a hard time finding what I want in the EVDL archives (there's a LOT
there, like drinking from the firehose). I'd like something comparable to
an 250-350hp ICE. Is that so much to ask?

Thanks all.
- Mark




On 12/3/07, Zeke Yewdall <[email protected]> wrote:
>
> Ah yes, how could I forget that.... I've never owned any vehicle
> with enough horsepower to matter -- 70 some HP just doesn't do it....
>  Actually, come to think of it, my EV is going to the most
> powerful vehicle I own when I get it done, at least in terms of peak
> power.
>
> Z
>
>


> John Wayland <[email protected]> wrote:
> > > Hello to Zeke and All,
> > >
> > > Zeke Yewdall wrote:
> ...


----------



## EVDL List (Jul 27, 2007)

> 
> I've never understood the attraction of rear wheel drive... but what
> if you put a front wheel drive transmission in the back of a car, and
> reversed the direction of motor rotation so the car still went
> forwards. That would essentially be the same as direct driving the
> rear differential, but with the benefit of a transmission... even if
> you did something like lock it in 2nd gear or something. Sort of like
> the VW bugs.

There is no need to reverse the direction of rotation in this setup, you move the fwd transaxle straight back to the rear end of the vehicle it is still driving forward, this is fairly commonplace and is a good way go


> Another idea... a typical 4wd transfer case is about 2:1 ratio....
> what if you got a divorced T-case and fed the motor into it, then
> drove the driveshaft from the output. Not sure how the losses of this
> and weight would compare to a transaxle. You'd also have to get a
> transfer case that could stand the RPM

your weight and losses would be far less than a full transmission, but make sure you get a t-case without any method of slip between the two outputs, this may also let you run a pair of motors, one driving the main input one driving the front axle output with a one-way slipper clutch for extra torque when needed but it disconnects and draws no power at speed and cruise?


> Or, use a part time 4wd subaru transmission, and take the front axle
> shafts out, with it in 4wd. They seem to be be strong enough to stand
> this for a while, depending on how much torque you are transmitting.

the rear output clutches on a subaru are very weak and light duty, Subarus are primarily a front wheel drive car, whose computer can push some torque to the rear wheels when needed but those trannies are not designed to run solely in rwd and won't do so for long, epecially with the torque of an electric drive and the weight of the batteries 

> The 4 wheelers who install a divorced transfer case and solid front
> axle on subaru's do this. Actually, if you are going to a rear wheel
> drive setup, you could use something like a 2wd S-10 transmission,
> with easily available motor adaptors, and then just fabricate customer
> motor/transmission mounts, and a custom driveshaft....

I think this is my favorite Idea although I think I'd use something like a 3 speed saginaw, you jdon't need as many gears as a gasser does and the three speed is lighter and easier to make custom shift linkages and put it where you want it, and because the rear diff is mounted solidly to the body you could push the trans all the way back to the diff, and keep the motor and trans in the tunnel like he wanted and leave the engine compartment open for batteries

> 


_________________________________________________________________
Connect and share in new ways with Windows Live.
http://www.windowslive.com/connect.html?ocid=TXT_TAGLM_Wave2_newways_112007
_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

> Zeke Yewdall wrote:
> > I've never understood the attraction of rear wheel drive...
> 
> I questioned that too. Until I drove a BMW.
> ...


----------



## EVDL List (Jul 27, 2007)

> The losses in a 60hz motor pushed to 400hz would be horrendous.

Why? It just needs higher voltage at lower current.
I would think that a possible problem could be the motor redline,
as 400 Hz on the usual 6 pole (3 pair) motor results in 8,000 RPM
but since many AC motors such as the AC Propulsion, the Prius and
the Tesla (as well as my own Hughes motor for my US Electricar)
have a redline in the range of 9,000 to 12,000 RPM, this does
not seem to be a problem.

Note that airplane designers deliberately chose 400Hz frequency to
make the transformers onboard lighter and more efficient.

I'd be interested to hear where 400Hz is less efficient, unless
you mean that the high amount of back-EMF is difficult to overcome
so there is a need for dynamic field weakening, which adds a little
current that is not contributing to the propulsion.

Cor van de Water
Systems Architect
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
Fax: +1 408 731 3675 eFAX: +31-87-784-1130
Second Life: www.secondlife.com/?u=3b42cb3f4ae249319edb487991c30acb

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Jeff Shanab
Sent: Monday, December 03, 2007 6:23 PM
To: [email protected]
Subject: Re: [EVDL] design input?

In EV sized motors, high rpm needs high frequency, high frequency needs special materials.

rpm = [freq(cycles/sec) * 60(seconds/min)]/(pole pairs) - slip so (60
* 60) / 2 (4 pole = 2 pole pair) == 3600/2 = 1800 rpm * .958 = 1725rpm

same motor on 50hz = 1437rpm
same motor at 400hz = 12,000 rpm

The losses in a 60hz motor pushed to 400hz would be horrendous. 120hz is about the limit.


_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

The Pontiac Fiero has a FWD transaxle moved to the
rear wheels. 

I built a lightweight single speed reduction gear
using the 3.25:1 planetary gears from the differential
or "final drive" gear of a FWD transmission. It was
coupled to a CVT belt drive, and weighed only 32lbs.
You could put one before each differential, but then
its doubling the weight.

I suggest you keep the 4WD and transmission and power
it with one big motor.

Jack



> --- Zeke Yewdall <[email protected]> wrote:
> 
> > I've never understood the attraction of rear wheel
> > drive... but what
> ...


----------



## EVDL List (Jul 27, 2007)

To put a finer point on the attraction of rear wheel drive:

The equations that show maximum acceleration include all kinds of
calculations of weight transfer. This determines the maximum tractive
force you can apply.

If you don't mind dialup performance, I have these links to some PHP
code that I wrote. I got the equations from racing books I have here. It
was the proof of concept for an online simulator. The data I used was my
guess for zombie vs gone postal a long time ago which theorizes if gone
postal could ever get hooked up it would be a hell of a race! There is
front to rear and left to right weight transfer involved. I had to guess
at too many criteria like spring rates and chassis stiffness.


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

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

> Cor van de Water <[email protected]> wrote:
> > > The losses in a 60hz motor pushed to 400hz would be horrendous.
> >
> > Why? It just needs higher voltage at lower current...
> ...


----------



## EVDL List (Jul 27, 2007)

Just note that the losses go up by the root of the freq,
so with 400 Hz iso 60 Hz the losses should be SQRT(400/60)
or about 2.5 times as high.
I am not familiar enough with motor design to tell you 
if that increase in losses will be compensated in some
way due to the lower current and high voltage when running
the same power, as my understanding is that eddy losses
are directly related to the amount of current, but I could
be wrong.

Regards,

Cor van de Water
Systems Architect
Proxim Wireless Corporation http://www.proxim.com
Email: [email protected] Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: [email protected]
Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925
Fax: +1 408 731 3675 eFAX: +31-87-784-1130
Second Life: www.secondlife.com/?u=3b42cb3f4ae249319edb487991c30acb

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Morgan LaMoore
Sent: Monday, December 03, 2007 10:56 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] design input?



> Cor van de Water <[email protected]> wrote:
> > > The losses in a 60hz motor pushed to 400hz would be horrendous.
> >
> > Why? It just needs higher voltage at lower current...
> ...


----------



## EVDL List (Jul 27, 2007)

> Mark Maher wrote:
> > Right. I've been wondering over the parameters involved in final drive
> > decision. All the motors on EVparts.com are DC and I haven't found any AC
> > torque curves. If a 10:1 is needed (is this specified?) then that may throw
> ...


----------



## EVDL List (Jul 27, 2007)

> > Or, use a part time 4wd subaru transmission, and take the front axle
> > shafts out, with it in 4wd. They seem to be be strong enough to stand
> > this for a while, depending on how much torque you are transmitting.
>
> the rear output clutches on a subaru are very weak and light duty, Subarus are primarily a front wheel drive car, whose computer can push some torque to the rear wheels when needed but those trannies are not designed to run solely in rwd and won't do so for long, epecially with the torque of an electric drive and the weight of the batteries
>

The AWD transmissions use computer controlled clutchs, however I was
referring to the 4wd ones that use an actual gear to engage rear wheel
drive -- it would hold up alot better, though with electric motor
torque... you might shear that little gear off.

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

>
>
> I think this is my favorite Idea although I think I'd use something like a
> 3 speed saginaw, you jdon't need as many gears as a gasser does and the
> three speed is lighter and easier to make custom shift linkages and put it
> where you want it, and because the rear diff is mounted solidly to the body
> you could push the trans all the way back to the diff, and keep the motor
> and trans in the tunnel like he wanted and leave the engine compartment open
> for batteries


I like this idea Robert. I'm not really familiar with the Saginaw 3sp, I'll
do some more finding out. Wondering if the bellhousing is removable for
packaging requirements if it were to be mounted in the rear. This also
gives me the idea of just using a dedicated lightweight transaxle to avoid
marrying a diff and tranny C5/C6 Corvette = overkill and $$$ but
maybe a 914... Although then I'd have to do some kind of adapter if I wanted
to keep the stock axles. But maybe it would be better to upgrade to
stronger ones anyway (Subaru axles a historical weak point). I wonder what
the weight difference would be....
_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

>> The losses in a 60hz motor pushed to 400hz would be horrendous.



> Cor van de Water wrote:
> > Why? It just needs higher voltage at lower current.
> > I would think that a possible problem could be the motor redline,
> > as 400 Hz on the usual 6 pole (3 pair) motor results in 8,000 RPM
> ...


----------



## EVDL List (Jul 27, 2007)

> Lee Hart wrote:
> >
> >> Note that airplane designers deliberately chose 400Hz frequency to
> >> make the transformers onboard lighter and more efficient.
> ...


----------



## EVDL List (Jul 27, 2007)

> Dan Frederiksen wrote:
> > what can you change to better fit the higher frequency?
> 
> Since the iron usually *is* the motor, changing the iron laminations to
> ...


----------



## EVDL List (Jul 27, 2007)

It was my understanding that 400hz is used because it's derived from a 
turbine-powered alternator which is a high RPM device.

It would have been difficult back in the day to make 60hz without gearing 
the system down.

-Phil
----- Original Message ----- 
From: "Dan Frederiksen" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Tuesday, December 04, 2007 4:23 PM
Subject: Re: [EVDL] design input?




> > Lee Hart wrote:
> >>
> >>> Note that airplane designers deliberately chose 400Hz frequency to
> >>> make the transformers onboard lighter and more efficient.
> ...


----------



## EVDL List (Jul 27, 2007)

To make matters worse. When you do have such high losses and things
begin to heat up, the efficiency takes a further nose dive.

The accumulation of heat can get ahead of you extremely fast.

" Over a temperature range 0-70^o C the resistance of copper wires
varies 28%."

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

> 
> 
> I like this idea Robert. I'm not really familiar with the Saginaw 3sp, I'll
> do some more finding out. Wondering if the bellhousing is removable for
> packaging requirements if it were to be mounted in the rear. This also
> gives me the idea of just using a dedicated lightweight transaxle to avoid
> marrying a diff and tranny C5/C6 Corvette = overkill and $$$ but
> maybe a 914... Although then I'd have to do some kind of adapter if I wanted
> to keep the stock axles. But maybe it would be better to upgrade to
> stronger ones anyway (Subaru axles a historical weak point). I wonder what
> the weight difference would be....


yes that bellhousing is removeable and interchangeable with several bolt patterns, the old 3 speed manuals are popular with dirt circle track guys because they are stong, light, and versatile which also makes them good for conversions, I have been meaning to look through the race areas for the flywheelless clutches that they use for reducing rotating mass, in an electric conversion the clutch is desirable but the mass of the flywheel is not and is not necessary I am trying to find a suitable clutchlike adapter that is not obscenely expensive to suggest to you guys

_________________________________________________________________
Connect and share in new ways with Windows Live.
http://www.windowslive.com/connect.html?ocid=TXT_TAGLM_Wave2_newways_112007
_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Hi Mark,

A lot of the things that make a Subaru a good EV racecar also make it a good 
candidate for a street conversion. It is fairly light and has a small 
frontal area. It is a popular car for racing and rallying, so there are 
upgraded parts available. Heavier springs, bigger brakes and light weight 
body parts are useful for an EV. The most important factor:

<I love Soobs >

Convert a car that you love because you will be putting some time into the 
job and a good conversion will last a long time.

<I have a few questions about your decision making process that I'm hoping
can help me with mine.>

We knew that our biggest challenge for closed circuit road racing would be 
range at speed. Road racing is the exact opposite of how to drive your car 
efficiently. We accelerate as hard as we can and then brake as hard as we 
can. Repeat until done.

We choose a AWD vehicle because we planned to maximize the energy we could 
recapture with regenerative braking. More detail here: 
http://www.proev.com/IAWDwhy.htm

We are now 'regenning' at 300 amps. This is enough so that we do not use the 
friction brakes on the road except in an emergency stop. In Miami city 
driving, we gain 10-15% range. Highway driving is closer 5%-10%.

On the track, we must combine regen with friction braking to slow as quickly 
as possible. Regen gives us 15%-20% better range. That means without regen 
our battery pack would have to be 1/5 heavier.

< I think you are running direct AC drives (both
motors mounted amidship of it's respective diff??), do you have any
reduction?>

The motors are bolted directly to two Subaru stock 3.9 rear differentials. 
On the stock 16' Sube WRX rims, we are turning 3,290 rpm at 60 mph. On race 
tires, we see 120 mph at about 7,000 rpm. The Siemens motors spin up to 
12,000 rpm but do not have a lot of torque up high.

The 3.9 ratio is in the right ball park for the tracks we are racing on. For 
the street or the perfect autocross car, we would do better with a ration 
around 5.5. This would give an under 4 second 0-60 time and a top speed of 
90 MPH.

The Subarus use the same diff as the Datsuns and Nissans, so there are a 
wider variety of ratios out there.

<My original idea was to ditch the tranny altogether and just run
direct drive to the rear diff only, and do electric reverse, have regen...
all that.>

I don't think it will be sporty enough with the stock Siemens offerings but 
the more powerful EVISOL controller should be available soon 
(http://www.metricmind.com/index1.htm) or AC Propulsions excellent but 
pricey drive (http://www.acpropulsion.com/technology/gen2.htm) would be 
nice.

< But now I'm thinking I need some kind of reduction so I might as
well keep the AWD >

We looked at using the Subaru automatic transmission. It uses 5 volt digital 
signals to initiate shifts and it is fairly easy to hack. We needed more 
power for racing than any of the available AC motors could give us, so we 
dropped the idea. It would have allow AWD regen and more flexibility in gear 
ratios. Concerns would be adding a transmission fluid pump and durability 
questions.

<but aren't AC motors kind of weaker in the
torque department compared with DC?>

The torque curves on the available traction DC and AC motors are very 
different. DC motors have amazing torque at low RPM but drop off very 
quickly. AC motors tend not to have the same initial torque but the torque 
curve is flatter and stays to a higher rpm.

<and do a big torquey DC motor (or maybe 2 ala White Zombie...) >

DC motors need either a transmission to keep the rpms in the sweet spot or 
two motors to allow a long gearing and still have good acceleration. I would 
tend towards the 2 motor direct drive because DC torque can trash 
transmissions.

I have spoken to one Subaru owner who is thinking about DC direct drive 
using stock rear diffs front and rear. This should make a very sporty 
vehicle. Custom front half shafts and fabricating a front crossmember will 
be required.

< A range of 30-50 miles of
semi-conservative driving would be good and I don't care about a top speed
of more than 85-90 mph or so, but I want something that is very quick from a
stoplight or on an onramp. Like WRX or STI level performance.>

I think this is very possible. There are lots of fun ways to get to this 
goal. I do not know which will work best.

Please let us know what you decide to try.

Cliff
www.ProEV.com



_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

Cliff,
I appreciate the detailed response. Lots of really good info and
recommendations. I found that the automatic 2.5 RS's have a 4.44:1 diff and
there is LSD options available there. And I've found some anecdotal
evidence that even 350whp has been put down through the stock units.

>I would
>tend towards the 2 motor direct drive because DC torque can trash
>transmissions.

When you said 2 DC motors do you mean married together or one per diff? If
I was going to do the 2 motor option I think the 2 married together running
to one diff would be a little simpler and then one could do the
parallel/series switch for greater range with the zilla 2k, right?

- Mark



> ProEV <[email protected]> wrote:
> 
> > Hi Mark,
> >
> ...


----------



## EVDL List (Jul 27, 2007)

Hi Mark,

Sorry about the delay replying.

> When you said 2 DC motors do you mean married together or one per diff? >

I was thinking one per diff but either would work.

> If I was going to do the 2 motor option I think the 2 married together 
> running
> to one diff would be a little simpler

Both ways will present some challenges. How do you plan to Siamese the two 
motors? Do you have enough space to fit the motors and how will they attach 
to the diff?

On the other hand, you would have to solve the whole 'mounting the second 
rear diff up front' problem if you do two diffs.

>and then one could do the parallel/series switch for greater range with the 
>zilla 2k, right?>

Is there any reason not to be able to do the whole series/parallel switch 
with the motors on different diffs?

Either way will make a good conversion. I just like the picture of all four 
wheels smoking off the line<G>.

Cliff
www.ProEV.com




_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev


----------

