EV Digest 2846
Topics covered in this issue include:
1) article: Land Speed Records: Advice
by Paul Wujek <[EMAIL PROTECTED]>
2) Re:Why did the Optimas explode?
by "Timothy Humphrey" <[EMAIL PROTECTED]>
3) RE: Li ion Cooling (Was: Li Ion Series Resistance)
by "Chris Tromley" <[EMAIL PROTECTED]>
4) Re: DC to AC
by "tom jackson" <[EMAIL PROTECTED]>
5) Re: Starting torque
by Rich Rudman <[EMAIL PROTECTED]>
6) Re: Why did the Optimas explode?
by Rich Rudman <[EMAIL PROTECTED]>
7) RE: 1958 Chevy Truck Conversion
by "Chris Tromley" <[EMAIL PROTECTED]>
8) Re: Why did the Optimas explode?
by Rich Rudman <[EMAIL PROTECTED]>
9) Re: Starting torque
by Gordon Niessen <[EMAIL PROTECTED]>
10) 2 speed transmission for racing?
by "Eric Penne" <[EMAIL PROTECTED]>
11) RE: 2 speed transmission for racing?
by "Dave Stensland" <[EMAIL PROTECTED]>
12) RE: 2 speed transmission for racing?
by "Eric Penne" <[EMAIL PROTECTED]>
13) Re: DC to AC
by Rich Rudman <[EMAIL PROTECTED]>
14) Re: Starting torque
by Peter VanDerWal <[EMAIL PROTECTED]>
15) RE: 1958 Chevy Truck Conversion
by Peter VanDerWal <[EMAIL PROTECTED]>
16) Re: Starting torque
by "Roderick Wilde" <[EMAIL PROTECTED]>
17) Re: 2 speed transmission for racing?
by "Roderick Wilde" <[EMAIL PROTECTED]>
18) RE: 2 speed transmission for racing?
by "Chris Tromley" <[EMAIL PROTECTED]>
19) Re: Li ion Cooling (Was: Li Ion Series Resistance)
by Victor Tikhonov <[EMAIL PROTECTED]>
20) Re: 2 speed transmission for racing?
by Victor Tikhonov <[EMAIL PROTECTED]>
21) Re: 1958 Chevy Truck Conversion
by "Thomas Shay" <[EMAIL PROTECTED]>
22) Re: Drag racing?
by "T Humphrey" <[EMAIL PROTECTED]>
23) RE: 2 speed transmission for racing?
by Gordon Niessen <[EMAIL PROTECTED]>
24) Re: 72V dc/dc
by "Lawrence Rhodes" <[EMAIL PROTECTED]>
25) eco-friendly transportation
by "Lawrence Rhodes" <[EMAIL PROTECTED]>
26) Re: Drag racing?
by [EMAIL PROTECTED]
27) RE: Drag racing?
by "Chris Tromley" <[EMAIL PROTECTED]>
28) More dc/dc questions, was: 72V dc/dc
by "The Levine Family" <[EMAIL PROTECTED]>
29) Re: Drag racing?
by "Roderick Wilde" <[EMAIL PROTECTED]>
30) Re: EV digest 2845
by Jeff Shanab <[EMAIL PROTECTED]>
--- Begin Message ---
Another article giving more information on the British team that is
trying to set a new battery powered EV land speed record (no I'm not
British, just reading news feeds from http://www.newsnow.co.uk).
Maybe, if someone knowledgeable about the team is on the list they can
forward more information.
article:
http://www.channel4.com/apps26/4car/jsp/main.jsp?lnk=211&id=5679
--
Paul Wujek
--- End Message ---
--- Begin Message ---
Two thoughts...
1. I thought Optima's were not supposed to gas, thus there should
be no hydrogen present in the battery box. Was a regulator system
used?
2. Possibly if no regulator system was used the Optimas did gas;
thus lowering the liquid level inside the battery, (I know with
AGM liquid is not really a proper term). Possibly low enough to
cause the plates to be exposed to a very hydrogen rich atmosphere,
especially right off from charge. Then driving (i.e. pulling big
amps) would turn the intercell connections (now dry) into big
heaters/ignitors, or maybe causing a plate to plate spark.
I'm not a battery engineer, the above is pure speculation.
Stay Charged! anyway
Hump
>
>
>-----Original Message-----
>From: Michael Hoskinson [mailto:[EMAIL PROTECTED]
>Sent: Wednesday, June 11, 2003 12:30 AM
>To: [EMAIL PROTECTED]
>Subject: Re: Why did the Optimas explode?
>
>
>Hmm. Ken's was not vented. Good thought.
>I think I'll vent mine. :)
>
>Mike
>
>Sheer Pullen wrote:
>> This makes it sound kind of like a hydrogen explosion - i.e. a
tiny
>> spark from a opening switch makes the battery go *boom*?
>>
>> Were both cars in question vented? Passive or active (with a
fan)?
>>
>>
>
--- End Message ---
--- Begin Message ---
Bryan Avery wrote:
> > An aluminum heatsink might be a challenge, as it is
> difficult to make
> a
> > good electrical connection to aluminum.
> > --
>
> Why would you have to make an electrical connection to the
> aluminum? All you need to transfer to the aluminum is the
> heat. Why not just use a copper buss bar between the
> batteries and clamp the aluminum heatsink somehow to the buss
> bar? Or am I missing something here?
Hi Brian,
Actually, you're missing the simple solution. The only reason aluminum
is used for heat sinks is that it's thermal conductivity is high *and*
it's relatively cheap. Copper has twice the thermal conductivity of
aluminum. It's just more expensive and heavier.
How about this? Make your buss bars out of a U-section of copper. The
distance between the legs of the U is slightly less than a flexible
hose. Push the hose into the rows of buss bars. Pump a non-conductive
coolant through the hose and you should be able to draw a big chunk of
heat out of your pack.
The danger here is that you'd have to keep the hose clean. You don't
want a conductive path of dirt connecting your buss bars!
Chris
--- End Message ---
--- Begin Message ---
> 1sclunn wrote:
> > I was thinking of something like a push-pull audio amp and play a
> > 60 or 50 cycle note into it. Yes, there would be some losses (60%
> > I believe) but a nice clean sine wave, would probably need 156v
> > to get the 170 peak peak then a step up transformer.
> lee wrote:
> That's a clever idea. It might even work! :-)
> Many years ago, when I first started experimenting with AC motor drives,
> I used a 4-channel stereo amplifier as my inverter. It was an easy way
> So, if you didn't want very much power (less than 100 watts) and didn't
> need the ultimate in efficiency, I think you could use an audio
> amplifier with a switchmode power supply (so it will work with a DC
> input) to generate 120vac.
A few years ago (approx 30) we modified several a.c. synchronous motor
telescope drives to run off 12 volt car batteries out in the field for
student use. The circuits were very simple. A crystal controlled 50Hz
timebase chip (UK) driving an audio amplifier chip (typically TDA2030 type)
driving a mains transformer in reverse i.e. into the 6V winding and out of
the 240V winding to drive the motor. Although we only needed a few watts of
drive in the initial units we scaled up the audio amplifier and transformer
bits to drive 10's of watts for other kinds of drives. We weren't interested
in efficiency it just had to be done quickly, work reliably and be cheap.
The last one of these drives was decommissioned last summer after around 25
years use. We used waveform generator chips and 555 timer chips also when we
wanted to switch to a slightly higher or lower speed (in order that a star
could be brought into the field of view of the telescope and locked onto the
50Hz drive to track on a equatorial mount). It didn't make a big difference
whether we used sine or square wave drive to the transformers in our case:-
the transformer filters out all the odd harmonics anyway to a smaller or
larger extent. We had cupboards full of second hand transformers and we
selected the ones that remained "coolest" in use!!! Not an approach I would
possibly take these days but acceptable for prototype and D.I.Y. use.
Regards
Tom Jackson
--- End Message ---
--- Begin Message ---
Roderick Wilde wrote:
>
> I concur with Rich on this subject. I believe Rich still remembers that run
> in Phoenix in 1996 when we put the Mazda up against a specially prepared EV1
> that had done 183 MPH. The GM dudes had just changed the gearing for drag
> racing and thought no one could touch them. Out from the shade tree came the
> little red Mazda. We lined up and when the lights dropped I must have been
> asleep. I awoke to see the EV1 launch ahead of me. For those who have never
> been to a drag race the Christmas Tree lights are a series of colored lights
> on two sides of a post that turn on in sequence as they drop down the pole.
> First is your staging light then Yellow, Yellow, Yellow then Green for GO!.
> The next light after Green is RED. You get this light instead of Green if
> you leave the starting line before the Green light. These lights are located
> about 15 to 20 feet from the starting light. Now back to the story. When the
> EVI launched ahead of me I nailed it and by the time we had reached the
> Christmas Tree lights I had passed the EV1 like it was standing still. Rich
> definitely remembers us later all screaming and chanting DC Rules, DC Rules!
> from the stands. In a sense this was part of the beginning of NEDRA as we
> all went to a pub and pizza place afterwards and discussed having a drag
> racing organization.
>
> Roderick
>
> Roderick Wilde, President, EV Parts Inc.
> Your Online EV Superstore
> www.evparts.com
> 1-888-EV Parts (387-2787)
> Phone: 360-385-7966 Fax: 360-385-7922
> PO Box 221, 107 Louisa Street
> Port Townsend, WA 98368
>
It's been 7 years plus since that night.
I still wanna beat the RX-7 with a home brew AC drive.
It's still not happened.
DC still rules the Drag strip.
--
Rich Rudman
Manzanita Micro
www.manzanitamicro.com
1-360-297-7383,Cell 1-360-620-6266
--- End Message ---
--- Begin Message ---
Sheer Pullen wrote:
>
> This makes it sound kind of like a hydrogen explosion - i.e. a tiny spark
> from a opening switch makes the battery go *boom*?
>
> Were both cars in question vented? Passive or active (with a fan)?
>
My guess is that the Zivan gassed the YT into a dry out condition. When
thier was a few hundred amp draw the rest of the pack(all 84 volts left)
caused a spark or ignition point inside the Yt with a dry cell and LOTS
of pressurized H2. And KaBlam!
I have never had a Yt or Rt explode. I have melted posts and seen folks
melt the interconnects, no explosions. In fact I have be come rather
complacent about it ever happening.
--
Rich Rudman
Manzanita Micro
www.manzanitamicro.com
1-360-297-7383,Cell 1-360-620-6266
--- End Message ---
--- Begin Message ---
Dennis Pestka wrote:
> I have not read much about people doing conversions without
> transmissions. I can see the all the advantages.
>
> What are the drawbacks and limitations to doing this?
Hi Dennis,
Mainly that you don't get the torque multiplication a transmission
provides. Granted, a series DC motor has *big* torque at the bottom
end, but a transmission in first gear has big multiplication too.
Most people use a transmission in conversions because it's there (free).
Starting from scratch, you can get the same result using no transmission
with a high-amp controller and batteries. Or with two motors and
series-parallel switching. I personally think the new Zilla controllers
with automatic series-parallel switching will become very popular with
trans-less EVs.
Chris
--- End Message ---
--- Begin Message ---
Timothy Humphrey wrote:
>
> Two thoughts...
>
> 1. I thought Optima's were not supposed to gas, thus there should
> be no hydrogen present in the battery box. Was a regulator system
> used?
>
> 2. Possibly if no regulator system was used the Optimas did gas;
> thus lowering the liquid level inside the battery, (I know with
> AGM liquid is not really a proper term). Possibly low enough to
> cause the plates to be exposed to a very hydrogen rich atmosphere,
> especially right off from charge. Then driving (i.e. pulling big
> amps) would turn the intercell connections (now dry) into big
> heaters/ignitors, or maybe causing a plate to plate spark.
>
> I'm not a battery engineer, the above is pure speculation.
>
> Stay Charged! anyway
> Hump
>
Same thought thread I had.
YTs Gas. Lead acid chemistry requiers it. But they recombine the H2 and
02. If there is is too much pressure the vent. Hence VRLA or Valve
regulated lead acid.
Dry plates and big amps is most likely right.
There should be a plug here for adjustable voltage regulated chargers
and battery regulators. And remote voltage monitors and displays.
does he have the proper charger for 72 volts???? This level of over
charge is kinda hard to fathom with anything even close to correct.
Rich Rudman
Manzanita Micro
www.manzanitamicro.com
1-360-297-7383,Cell 1-360-620-6266
--- End Message ---
--- Begin Message ---
What exactly is the reluctance in using a transmission to shift from lower
to high gear to give both starting torque and high speed power. The
efficiency of the transmission can't be that bad. Even a two speed
transmission should be able to move the AC motor into a more efficient
power band to recapture the transmission loss. Or am I missing something?
Gordon
--- End Message ---
--- Begin Message ---
Somebody on the list was using a 2 speed transmission for racing that they
bought. The tranny was very robust and the company said it would not
break for anything. Who was it and where can I find out more information
on the tranny?
I've done a google search but it's not exactly what I was looking for. If
I recall correctly it was very small.
Eric
--- End Message ---
--- Begin Message ---
Maybe you're thinking of someone else, but NetGain's Bad Amplitude uses
the same Lenco air-shifted 2 speed that is often used in monster gas
dragsters...
http://www.go-ev.com/vehicles/bad_amplitude.shtml
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
Behalf Of Eric Penne
Sent: Wednesday, June 11, 2003 11:31 AM
To: [EMAIL PROTECTED]
Subject: 2 speed transmission for racing?
Somebody on the list was using a 2 speed transmission for racing that
they
bought. The tranny was very robust and the company said it would not
break for anything. Who was it and where can I find out more
information
on the tranny?
I've done a google search but it's not exactly what I was looking for.
If
I recall correctly it was very small.
Eric
--- End Message ---
--- Begin Message ---
That's exactly who I was looking for. Thanks!
> Maybe you're thinking of someone else, but NetGain's Bad Amplitude uses
> the same Lenco air-shifted 2 speed that is often used in monster gas
> dragsters...
>
> http://www.go-ev.com/vehicles/bad_amplitude.shtml
>
--- End Message ---
--- Begin Message ---
Lee Hart wrote:
>
> The simple answer is that perfect sinewaves aren't needed, and that even
> crude 6-step waveforms give you 90% or more of a motor's sinewave
> performance and efficiency.
> --
That was my point on the E-cycle controller thread.
That last %10 can really be hard to get.
Rich Rudman
Manzanita Micro
www.manzanitamicro.com
1-360-297-7383,Cell 1-360-620-6266
--- End Message ---
--- Begin Message ---
On Wed, 2003-06-11 at 10:11, Gordon Niessen wrote:
> What exactly is the reluctance in using a transmission to shift from lower
> to high gear to give both starting torque and high speed power. The
> efficiency of the transmission can't be that bad. Even a two speed
> transmission should be able to move the AC motor into a more efficient
> power band to recapture the transmission loss. Or am I missing something?
>
The issue is mostly weight and space, and to a lesser extent
efficiency.
Depending on the transmission, typical trannies run 90 to 95%
efficient. Therefor, to be useful, the transmission needs to make more
than a 10% improvement in the AC drive's efficiency.
Except near the edges of it's torque band, AC drives tend to be within
10% across the band. So the Transmission only really helps out a bit at
start up, but costs you efficiency during the rest of the power band.
A high efficiency, two speed transmission could really make a difference
here, unfortunately I'm unaware of anyone making such an animal at this
point in time.
--- End Message ---
--- Begin Message ---
On Wed, 2003-06-11 at 04:35, Pestka, Dennis J wrote:
>
> I have not read much about people doing conversions without transmissions.
> I can see the all the advantages.
>
> What are the drawbacks and limitations to doing this?
>
The main drawback is torque. In the typical transmission 4th gear is
about a 1:1 ratio, i.e. the input shaft is spinning at the same speed as
the output shaft. First gear is around 3:1, three revolutions of the
input (motor) for every revolution of the output AND at the same time
the output shaft produces three times the torque of the motor. Second
gear is around 2:1, etc.
So without a transmission you are stuck in 4th gear all the time. In
order to provide the same performance accelerating from a stop, your
motor now needs to provide about three times as much torque. This means
(for a series motor) that you will need somewhere between two and three
times as much current going into the motor. This means a more powerful
controller (more expensive). In order to avoid a melt down you will
also need either two motors (similar in size to the single motor with
transmission) or one much larger motor (again more expensive). Finally
you are going to need more powerful batteries to feed this
motor/controller combo.
Now as I recall you want to convert a truck, that is already quite
heavy, into a performance vehicle?
To get high performance with a heavy vehicle requires a very powerful
motor/controller combo. To do it without a transmission requires an
enormously powerful motor/controller.
Probably talking at least one, possibly two, 'zilla 2k controllers and
two or three Warp motors. I'm not sure where you are going to find high
power batteries that can feed this combo and weigh less than 1,000 lbs,
probably some Hawkers or SVRs.
You were planning on spending about $20,000 on the EV drive system
right? If you can afford $30K you might try going with a double AC
drive setup, that might give you the performance you want...if you can
find the batteries to feed it.
--- End Message ---
--- Begin Message ---
Lee, Thanks for the great post! Very clear and concise as always. I like
your idea of half mechanical and half electronic commutation. You could call
it a hybrid system ;-)
Roderick
----- Original Message -----
From: "Lee Hart" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, June 10, 2003 11:47 PM
Subject: Re: Starting torque
> Seth wrote:
> > I think it has something to do with needing three 2000amp half
> > bridges instead of one, for starters.
>
> Exactly so.
>
> A series motor tends to multiply torque. In theory, Torque =
> FieldCurrent x ArmatureCurrent. Since the field and armature are in
> series, this becomes Torque = Current^2. The torque per amp at high
> currents is fantastic.
>
> In practice, magnetic saturation limits the actual torque to something
> less than current^2. The exponents is somewhat smaller than 2. However,
> as long as it is more than current^1, the series motor beats just about
> any other type at supplying high torque.
>
> An AC induction motor has Torque = Current^1. You only get high torque
> with high current. Now, the inverter is stepping the voltage down, and
> so stepping the current up. But the transistors and diodes in the
> inverter still have to be sized to carry the peak current. To get 1000
> motor amps, you need 1000-amp semiconductors.
>
> Thus, the AC inverter is going to need something like 6 times the
> silicon to match an equivalent series motor. Possible; but expensive!
>
> > people like me can do modest, crude power (200A) for a buck converter
> > for a series or PM brush motor. But asynchronous AC... I hear about
> > space vector, third harmonic, eigen this or that and the other.
>
> All this is just to optimize efficiency -- not raw horsepower or torque.
> If you want maximum starting torque, it's easy. Hit the motor with its
> slip frequency at full pack voltage, and get out of the way! That motor
> is going to start turning -- or break something!
>
> > now I know Rich is allergic to white lab coats ;-)
>
> Not from lab technicians; from the doctors at that hospital that applied
> all those 2x4 "treatments" (Drs. Dube, Wayland, Wilde, et. al. (I'm only
> kidding, folks :-)
>
> > maximum stall torque per transistor to make the "electronic
> > transmission" a reality is a very important goal, from a
> > marketability point and saving costs on the controller. "We
> > haven't figured out the motor math yet, so we just use 800 amp
> > modules for 35kW at 336VDC and hey, 750 watt-hours per mile
> > isn't bad for a compact car" isn't going to cut it at review
> > time for *that* motor engineer.
>
> Very true. The inverter and AC motor for an on-the-road EV has to be
> very efficient; it is competing against the much cheaper DC series motor
> and PWM controller, which are 80% efficient or better. If your AC drive
> can't beat it, you don't have a product!
>
> But for drag racing, efficiency per se is not all that important. You're
> only going to be racing for a matter of seconds. The series DC motor and
> PWM controller is only 50% efficient under these conditions. So your AC
> drive doesn't have to be 90% efficient; even 60% will do.
>
> But, nobody is designing an AC drive for these conditions. They could!
> -- they just aren't. There are enough examples of very high power AC
> drives to show that they are possible. TV antenna rotators use tiny
> 2-phase AC motors to move monsterous antennas. There are 400 Hz AC
> aircraft motors for moving flaps and landing gear; applications that
> demand very high power for very short lengths of time. Torpedo motors
> are another example.
>
> I honestly think the way to build an AC motor with extremely high peak
> power is with a hybrid inverter. Half transistors, half mechanical
> switches (commutator). The mechanical switches do the work at full
> throttle. The transistors take over at anything less, when more finesse
> is called for.
> --
> Lee A. Hart Ring the bells that still can ring
> 814 8th Ave. N. Forget your perfect offering
> Sartell, MN 56377 USA There is a crack in everything
> leeahart_at_earthlink.net That's how the light gets in - Leonard Cohen
--- End Message ---
--- Begin Message ---
We also use a two speed transmission in the "Maniac Mazda" it is a TCI race
GM powerglide with no torque converter. With 2800 amps of motor torque
providing over 1000 foot pounds of torque multiplied by 1.78 for first gear
times another 4.11 for the rear axle ratio gives you over 7000 foot pounds
of torque on the giant Moser axles. I would say 7000 foot pounds is a good
place to start if you want to launch hard ;-)
Roderick
Roderick Wilde, President, EV Parts Inc.
Your Online EV Superstore
www.evparts.com
1-888-EV Parts (387-2787)
Phone: 360-385-7966 Fax: 360-385-7922
PO Box 221, 107 Louisa Street
Port Townsend, WA 98368
----- Original Message -----
From: "Eric Penne" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, June 11, 2003 9:30 AM
Subject: 2 speed transmission for racing?
> Somebody on the list was using a 2 speed transmission for racing that they
> bought. The tranny was very robust and the company said it would not
> break for anything. Who was it and where can I find out more information
> on the tranny?
>
> I've done a google search but it's not exactly what I was looking for. If
> I recall correctly it was very small.
>
> Eric
>
>
--- End Message ---
--- Begin Message ---
Roderick Wilde wrote:
> We also use a two speed transmission in the "Maniac Mazda" it
> is a TCI race GM powerglide with no torque converter. With
> 2800 amps of motor torque providing over 1000 foot pounds of
> torque multiplied by 1.78 for first gear times another 4.11
> for the rear axle ratio gives you over 7000 foot pounds of
> torque on the giant Moser axles. I would say 7000 foot pounds
> is a good place to start if you want to launch hard ;-)
Hmmm, I don't know much about drag racing and there are probably a lot
of subtle nuances involved. But if I take a crude whack at the numbers
with some guesses inserted, here's what I come up with.
Let's say the Maniac weighs 2000 lbs., and all of it transfers to the
rear wheels at launch. Let's say your track/tire coefficient of
friction is 3. And that your rolling radius is 1 ft. That tells me you
can only put 6000 foot pounds on the track. The weight and coefficient
numbers are probably a bit high, meaning your maximum usable torque is
even less. It also seems to me that if you have WAY too much torque
available it gets to be a real handful to control at launch.
Would it not be a good approach to gear so you have only a little excess
torque at launch, meaning you're pulling low revs and big torque for the
longest possible time?
Searching for enlightenment,
Chris
--- End Message ---
--- Begin Message ---
A solution I was considering for a while was just to deep
all the cells in a box being a tank filled with circulating water.
Each cell is a molded plastic can with seam at the top edge,
so don't care about water outside.
If tops between cells are sealed around (with RTV silicone
or similar), the water will not get on the surface.
I won't do it because for my conditions I believe
forced air cooling will be sufficient, but cooling
the cells directly in water is best way to take heat away.
Sealing top surface will be a challenge though.
Victor
Chris Tromley wrote:
>
> Bryan Avery wrote:
>
> > > An aluminum heatsink might be a challenge, as it is
> > difficult to make
> > a
> > > good electrical connection to aluminum.
> > > --
> >
> > Why would you have to make an electrical connection to the
> > aluminum? All you need to transfer to the aluminum is the
> > heat. Why not just use a copper buss bar between the
> > batteries and clamp the aluminum heatsink somehow to the buss
> > bar? Or am I missing something here?
>
> Hi Brian,
>
> Actually, you're missing the simple solution. The only reason aluminum
> is used for heat sinks is that it's thermal conductivity is high *and*
> it's relatively cheap. Copper has twice the thermal conductivity of
> aluminum. It's just more expensive and heavier.
>
> How about this? Make your buss bars out of a U-section of copper. The
> distance between the legs of the U is slightly less than a flexible
> hose. Push the hose into the rows of buss bars. Pump a non-conductive
> coolant through the hose and you should be able to draw a big chunk of
> heat out of your pack.
>
> The danger here is that you'd have to keep the hose clean. You don't
> want a conductive path of dirt connecting your buss bars!
>
> Chris
--- End Message ---
--- Begin Message ---
Bruce Meland uses custom 2 speed transmission in his drag bike.
Victor
Eric Penne wrote:
>
> Somebody on the list was using a 2 speed transmission for racing that they
> bought. The tranny was very robust and the company said it would not
> break for anything. Who was it and where can I find out more information
> on the tranny?
>
> I've done a google search but it's not exactly what I was looking for. If
> I recall correctly it was very small.
>
> Eric
--- End Message ---
--- Begin Message ---
----- Original Message -----
From: "Pestka, Dennis J" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, June 11, 2003 4:35 AM
Subject: RE: 1958 Chevy Truck Conversion
>
> I have not read much about people doing conversions without transmissions.
> I can see the all the advantages.
>
> What are the drawbacks and limitations to doing this?
>
> Dennis
> Elsberry, MO
Without a transmision you have a fixed gear ratio which I think said was
3.90:1
This ratio would work reasonable well at about 70 mph on the level but not
for starting and hillclimbing where a ratio of about 10:1 to 15:1 would be
optimum. A standard transmission allows gear ratios to be selected to suit
various driving conditions.
People who build EVs without transmissions resort to various measures to
make up for the torque multiplication of the lower gears in a transmission.
They use high controller currents and usually dual motors. Some with dual
motors shift the connections of motors between series and parallel. All of
this seems like a lot of trouble just to avoid using a transmission.
The EV-1 with its AC drive uses a fixed ratio transmission with about 13:1
ratio. This provides good torque for climbing and acceleration. The need
to upshift to higher gears is avoided by using a motor that can run up to
about 12,000 rpm. The DC motors commonly used in conversions can't
run that fast.
The Sparrow uses the same DC motor as used in many conversions with
a toothed belt drive with 5.625:1 ratio. It's light weight, about 1300 lbs
plus driver, makes it to possible to get along without a transmission to
provide additional gear reduction for acceleration and climbing.
Tom Shay
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I'm not a drag racer either . ....yet!
But the way I think it works is you want hard pulling torque at
the launch, hard pulling torque in the middle, and hard pulling
torque at the end. Basically you want to be accellerating all the
way past the end of the run.
Now we know that a DC motor's torque starts to diminish as it
Rev's up, so we need to start with way too much torque in order to
have enough for the upper speeds. This is where transmissions come
in handy, or series-parallel shifting or some other torque-
shifting contraption.
I was thinking maybe something like a CVT that keeps a motor right
at 1000rpm (or some other sweet spot) all the way
through ....ooooh .....saaaay ......250mph! If the batt's could
belt out 2800amp for 13 seconds.....hmmmmm!
I don't know the math. Chris, how fast would the Mazda be going
after 13 seconds if it were delivered a CONSTANT 6000 ft lbs at
the pavement. How far will it have travelled? How long would it
take and how fast would it be going at 1320ft. Use your below
assumptions as needed.
Stay Charged!
Hump
>
>
>-----Original Message-----
>From: Chris Tromley [mailto:[EMAIL PROTECTED]
>Sent: Wednesday, June 11, 2003 3:52 PM
>To: [EMAIL PROTECTED]
>Subject: RE: 2 speed transmission for racing?
>
>
>Roderick Wilde wrote:
>
>> We also use a two speed transmission in the "Maniac Mazda" it
>> is a TCI race GM powerglide with no torque converter. With
>> 2800 amps of motor torque providing over 1000 foot pounds of
>> torque multiplied by 1.78 for first gear times another 4.11
>> for the rear axle ratio gives you over 7000 foot pounds of
>> torque on the giant Moser axles. I would say 7000 foot pounds
>> is a good place to start if you want to launch hard ;-)
>
>Hmmm, I don't know much about drag racing and there are probably
a lot of
>subtle nuances involved. But if I take a crude whack at the
numbers with
>some guesses inserted, here's what I come up with.
>
>Let's say the Maniac weighs 2000 lbs., and all of it transfers to
the rear
>wheels at launch. Let's say your track/tire coefficient of
friction is 3.
>And that your rolling radius is 1 ft. That tells me you can only
put 6000
>foot pounds on the track. The weight and coefficient numbers are
probably a
>bit high, meaning your maximum usable torque is even less. It
also seems to
>me that if you have WAY too much torque available it gets to be a
real
>handful to control at launch.
>
>Would it not be a good approach to gear so you have only a little
excess
>torque at launch, meaning you're pulling low revs and big torque
for the
>longest possible time?
>
>Searching for enlightenment,
>Chris
>
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Doesn't the TZero have active traction control to avoid tire spin? I
wonder if it does it by monitoring motor load or tire rotation?
Would it not be a good approach to gear so you have only a little excess
torque at launch, meaning you're pulling low revs and big torque for the
longest possible time?
Searching for enlightenment,
Chris
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http://www.excess-solutions.com/ Ask them about the 25 to 50 watt DC to DC
converters. They accept up to 48 to 63vdc Make 5v and 12v at 25watt. This
time I didn't see anything above 25watt which is think is 1amp. Lawrence
Rhodes.......
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----- Original Message -----
From: "garry" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, June 11, 2003 3:12 AM
Subject: Re: 72V dc/dc
> Hi Lawrence,
>
> Do these guys have a web site for those of us who are out of the area, or
in
> my case out of the country ?
>
> I have just got my 72 volt car going today and I could probably do with a
> few of these.
>
> thanx
>
> Garry Stanley
>
> Cable.net.nz
>
>
>
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--- Begin Message ---
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Lets see,if the wheelie popping manic masda that pulled .9sec 60ft. times
could keep that pace up the whole qt.mi.,it would run 3 seconds faster than my
Current eliminator dragster.Ice drag cars with .9sec 60fts. run in the 5s in
the qt.mi. Rod get some fresh lead in
that slead,and let 2x4 Rudman re- engineer your dc motor,so it will pull the
whole way.
Dennis Kill A Watt Berube 8sec.ev
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T Humphrey wrote:
> But the way I think it works is you want hard pulling torque at
> the launch, hard pulling torque in the middle, and hard pulling
> torque at the end. Basically you want to be accellerating all the
> way past the end of the run.
This is true, but the limit at launch is traction. You want to keep
your tires on the verge of spinning, but not spinning. Too much torque
makes this hard to control. If they spin, you lose traction and
therefore thrust.
> Now we know that a DC motor's torque starts to diminish as it
> Rev's up, so we need to start with way too much torque in order to
> have enough for the upper speeds. This is where transmissions come
> in handy, or series-parallel shifting or some other torque-
> shifting contraption.
That's why I suggested you gear the car higher so it just chirps the
tires at launch. The higher gear keeps you pulling longer and harder
before you have to shift.
> I was thinking maybe something like a CVT that keeps a motor right
> at 1000rpm (or some other sweet spot) all the way
> through ....ooooh .....saaaay ......250mph! If the batt's could
> belt out 2800amp for 13 seconds.....hmmmmm!
I believe the sweet spot depends on your controller. Max power is the
point where your controller comes out of current limit. (I think
constant current means constant torque? But power is torque x rpm.
Hmmm, this means the higher gear may not be the answer.) Power drops
steadily from there.
> I don't know the math. Chris, how fast would the Mazda be going
> after 13 seconds if it were delivered a CONSTANT 6000 ft lbs at
> the pavement. How far will it have travelled? How long would it
> take and how fast would it be going at 1320ft. Use your below
> assumptions as needed.
That assumes constant acceleration, which is relatively easy to
calculate. In this case your coefficient of friction is equivalent to
lateral acceleration in g's, or 3 x 32.2 ft/s/s = 96.6 ft/s/s. It has
little to do with reality, however. For example, I doubt you can
sustain a coefficient of friction of 3 outside the launch area. Aero
losses account for a big drop in acceleration at high speeds. So
there's a real danger in relying on calculations like this. (I can hear
the real racers snickering already.)
Anyway, here goes. By my calculations, in 13 seconds the Maniac Mazda
would be trundling along at 856 mph. Distance traveled is 1.5 miles.
The quarter mile would be covered in 5.23 second at 505 mph. So much
for calculations, at least overly simplistic ones like this. FWIW, a
constant 1 g acceleration gives a quarter mile run of 9.05 seconds at
198.8 mph. Acceleration at the strip ain't constant.
It would be educational to see a simulation that factors in the
traction-limited phase, the constant-torque phase, the rise in aero
losses, changing coefficient of friction at different points on the
track, and anything else I've missed. But then, reality is all that
matters.
Chris
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>>>http://www.excess-solutions.com/ Ask them about the 25 to 50 watt DC to
DC
converters. They accept up to 48 to 63vdc Make 5v and 12v at 25watt. This
time I didn't see anything above 25watt which is think is 1amp.<<<
I still haven't played with my DC-to-DC converters, but being rated for
34-75V input means you'd need 2 with series input to handle a 72V pack (my
Kewet is 48V). They are dual output: either [EMAIL PROTECTED] or [EMAIL PROTECTED],
but I do have
a couple dozen to work with. The Kewet does not have an auxillary 12v
battery - would it be better at 13.2V or 15V; do I need to add a battery; do
I charge it all the time off the main pack or only when turned on, and at
which voltage?
Any idea how much wattage I need for peak use? I also plan on replacing the
cheap radio, not for Plasma-Boy-breaking-eardrums levels, just enough to
enjoy the weaker channels. I can hook up 8 of them for [EMAIL PROTECTED], 6 for
[EMAIL PROTECTED], or 9 for [EMAIL PROTECTED] I don't need a new dc/dc, just want to
try to
make up my own (even 9 of these units would be smaller than what came with
the car).
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I would love to see a .9 second 60 ft. time. I just looked in a file with
some early time slips and at Bremerton when we were doing low 11 ETs the 60
ft. times were in the 1.4s. at 108 to 112 MPH terminal speed. Top end
suffers from not seeing much voltage at the motors. We only saw about 100
volts from the 216 volt pack. A gas car with 1.4's runs 130 to 140 something
MPH in the quarter. To keep an EV pulling you MUST run high voltage.
Roderick
Roderick Wilde, President, EV Parts Inc.
Your Online EV Superstore
www.evparts.com
1-888-EV Parts (387-2787)
Phone: 360-385-7966 Fax: 360-385-7922
PO Box 221, 107 Louisa Street
Port Townsend, WA 98368
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Wednesday, June 11, 2003 1:12 PM
Subject: Re: Drag racing?
> Lets see,if the wheelie popping manic masda that pulled .9sec 60ft. times
> could keep that pace up the whole qt.mi.,it would run 3 seconds faster
than my
> Current eliminator dragster.Ice drag cars with .9sec 60fts. run in the 5s
in
> the qt.mi. Rod get some fresh
lead in
> that slead,and let 2x4 Rudman re- engineer your dc motor,so it will pull
the
> whole way.
> Dennis Kill A Watt Berube 8sec.ev
--- End Message ---
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On Tue, 2003-06-10 at 22:55, Jeff Shanab wrote
Isn't it all AC after commutation?
Correct me if I am wrong, i have been trying to naildown motor
characteristics for a while.
Do we mean induction vs Commutation ?
The series motor has the guts off the line because of low rotor voltage,
very low back emf.
Umm, no. Well at least not directly. Off the line the series motor
might have very high rotor voltage.
What gives it it's high torque is that the huge current going through
the rotor is ALSO going trough the field and producing TWO large
magnetic fields (field and armature). Theoretically doubling the
current in a series motor results in four times the torque, reality is
generally less than that due to saturation, etc.
either magnet or rotor windings create back emf as rpm increases
subtracting from avail torque. The comutator gives you a freq range down
to 0hz.
back emf does not subtract from torque unless it causes the current to
drop. Most racing controllers are current limited until very close to
the end anyway.
ok, got it. But isn't that large current flow enabled by the voltage difference?
when the back emf = your applied voltage, current flow is zero and torque is
zero(almost) and we are at no load rpm.
If back emf is greater than applied voltage, er, you are regenerating?
ok, that is the "not directly" of which you spoke.
Induction motor has currents induced in bars due to slip, So much at
start that heat is a major problem. what is the minimum frequency of an
automotive sinewave(AC) drive?
Heat is a major problem in ANY motor with huge currents flowing.
If I load a series wound motor down, the field and stator both get hot, the heat is from losses during creation of work producing torque. I think it is pretty linear?
If I load an Induction motor to where it doesn't make pull out torque the rotor bar current is a function of the slip and can get way hotter than stator. Not really work related, just waste. Very unsuitible for drag racing loads.
I looked at BLDC and the loss of torque at higher RPM's concerned me, no field weekening avialible (efficiently) but I like the simplicity(eats trapazoidal waveforms) and potencial efficiency and regen capabilities.
I looked at SRM, then I looked again, Ok, I need to look at them again, I still don't understand how they can work in an EV.
Then I found what I thought would be the ideal motor, the slip-ring motor. You can run it with 50% slip without burning up the motor, the heat causeing current is allowed to escape out the rotor slip rings. it can be re-used. Injecting a voltage can lock into syncronization and the efficiency can be bumped up a notch. Has anyone tryied using a slip-ring motor? If they can start rock crushers under load off of line frequency, sounds pretty axle braking to me.
I want regen, I want efficency, I want gobs of torque, I want a short range vehicle that is fun and can be autocrossed. I have been tending toward BLDC at the moment. but only if I wind my own. those suckers are expensive!
What I would like to find/create is a web page of motor torque charts for all the different motor/contoller combinations out there. Like "series on PWM" BLDC on trap,6step,sine induction on fixed frequency, variable freq, etc.
then there are the segmented array (to hard to get) and the ironless rotor (also to hard to get)
Thanks EVlist for all the info, Even if I don't post often, I read every night and am constnatly upgrading the plan for my first EV.
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