GameboyRMH PowerDork
Nov. 16, 2012 11:34 a.m.

Interesting project I ran across:

http://kurtsprojects.blogspot.com/

911 with paddle-shiftable slushbox converted to an EV. He said he's taken it up to 100mph so far and it will get about 50 miles of range once all the batteries are in, but he hasn't posted any 0-60 times because the slushbox is causing no end of trouble.

Woody MegaDork
Nov. 16, 2012 11:37 a.m.

I'm fairly certain that I know someone who would be interested in this...

Raze SuperDork
Nov. 16, 2012 1:42 p.m.

While I was skeptical at first, I'm actually thinking this is pretty cool...

MrJoshua PowerDork
Nov. 16, 2012 1:49 p.m.

That is pretty cool. Crappy energy efficiency though. Sounds like he has more work to do to get it right. Definitely a harder job with modern auto transmissions.

Nashco
Nashco UltraDork
Nov. 16, 2012 4:19 p.m.
MrJoshua wrote: That is pretty cool. Crappy energy efficiency though. Sounds like he has more work to do to get it right. Definitely a harder job with modern auto transmissions.

Not quite sure why he's using the autotragic (goes against everything you'd want in an EV), but with that and the DC motor and controller he's using (not to mention not-low-rolling resistance tires), I'm not sure he's going to see anywhere close to the numbers he wants to see for efficiency. Neat project, but I just can't warm up to DC motors.

Bryce

iceracer UltraDork
Nov. 16, 2012 4:47 p.m.

He should have eliminated the "slushbox:.

With the torque of the electric motor, very little if any transmission is needed.

MrJoshua PowerDork
Nov. 16, 2012 7:46 p.m.

In reply to Nashco:

It's hard to argue a new motor/controller combo for $6k that will do 300hp. An AC equivalent would be well north of $30k. Sure you lose regen and you do have to replace brushes every 100k or so but all that extra money can be used for more or better batteries. The nicest feature of the autotragic is being able to idle and keep the accessories powered up with a simple drive system. That combined with the sticky tires does hurt efficiency but he still is getting about 1/2 the efficiency he should. It is so bad that I am suspicious of bad math or not starting with a truly charged pack.

MrJoshua PowerDork
Nov. 16, 2012 7:56 p.m.
iceracer wrote: He should have eliminated the "slushbox:. With the torque of the electric motor, very little if any transmission is needed.

That is unfortunately a myth of the electric motor drivetrain. Yes they produce a lot of torque, but they are limited by battery and controller capacity. The controller he is using is one of the better ones out there and capable of delivering 1000 amps. At 1000 amps that motor produces around 300 ft/lbs of torque. That means is a car that comes with 300 ft/lbs of torque from the factory you would be slower than a stock version until the stock one got into forth or fifth gear(1/1). There is a 2000amp controller but it is a little uppity and more expensive. There is even a 3000 amp controller but it is $10k and you would need a LOT of battery and motor to make use of it.

HappyAndy Dork
Nov. 16, 2012 8:32 p.m.

Meh, I'm not impressed. DC motors are for amateurs, and like Nashco said the auto trans does nothing usefull for an EV.

MrJoshua PowerDork
Nov. 16, 2012 8:41 p.m.
HappyAndy wrote: Meh, I'm not impressed. DC motors are for amateurs, and like Nashco said the auto trans does nothing usefull for an EV.

If you want to build one that has any performance for yourself you will likely end up with DC.

Auto trans eliminates fabricating an entire new AC setup, fabricating an entire new power steering setup, fabricating an entire new electrical supply system for your car, etc... It also shifts gears so you don't have to like some 99% of all American car owners want.

MrJoshua PowerDork
Nov. 16, 2012 8:45 p.m.

An interesting twist to the AC/DC debate is the Azure Dynamics did just go bankrupt and get liquidated at auction. There will be a BUNCH of really nice AC systems for sale at great prices once all the buyers get their purchases organized.

mad_machine MegaDork
Nov. 16, 2012 8:58 p.m.

electric motors also make the most torque at zero RPMs.. so a transmission is a good thing for performance AND range

MrJoshua PowerDork
Nov. 16, 2012 9:19 p.m.

OK-here is a way to a cheaper AC system than was previously available.

$3kAzure dynamics auction motor

$6k Aus Normal priced Tritium Wavesculptor

That will get you about 175hp.

When the Azure auction controllers hit the market you might be able to get the price of a controller similar to the Tritium for around $3k.

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