Cool electric Z-car project

[280Z Turbo]

I thought this was pretty neat. It's a DC powered 240Z.

The Hybrid Z thread:

http://forums.hybridz.org/showthread.php?t=132837

The website:

http://ampeater.wordpress.com/

[GoCougs]

Interesting, but the motor is only rated at 20hp. He might be able to get 40hp or maybe 60hp for really short bursts (on the order of seconds), but that's about it.

[280Z Turbo]

"The motor controller is a 144v/156v unit capable of 1000Amps, pumping out 144,000 watts peak. This works out to 156hp, but several hundred ft/lbs of torque."

[AmpEater]

Interesting, but the motor is only rated at 20hp. He might be able to get 40hp or maybe 60hp for really short bursts (on the order of seconds), but that's about it.

http://www.youtube.com/watch?v=g5_Ft8q3QmM

250 ft/lbs for as long as I dare hold the pedal down

[Soup DeVille]

"The motor controller is a 144v/156v unit capable of 1000Amps, pumping out 144,000 watts peak. This works out to 156hp, but several hundred ft/lbs of torque."

That's the motor controller, not the motor.

However, I know from experience that industrial electric motors are rated with a huge safety factor and can in fact draw much more than their rated amperage for quite a long time.

[GoCougs]

http://www.youtube.com/watch?v=g5_Ft8q3QmM

250 ft/lbs for as long as I dare hold the pedal down

But 20 hp is 20 hp. (And regarding the controller's 144,000 watts; 144 kW = 189 hp, not 153 hp.)

My experience is that DC motors are more limited in overload as their coils are on the rotor, limiting the ability to dissipate heat. However, I've not heard of this motor mfr, so perhaps it's built for sustained overloading. And there's always liquid cooling!

And I sure hope there's some fusing and circuit protection that is simply not shown in the pictures!

[Soup DeVille]

But 20 hp is 20 hp. (And regarding the controller's 144,000 watts; 144 kW = 189 hp, not 153 hp.)

And I sure hope there's some fusing and circuit protection that is simply not shown in the pictures!

I'm sure he's reducing it somewhat for efficiency factors.

Ehh, what's the point of experimenting like this if there's no chance of melting the rubber off of your wheels, eh?

[AmpEater]

But 20 hp is 20 hp. (And regarding the controller's 144,000 watts; 144 kW = 189 hp, not 153 hp.)

My experience is that DC motors are more limited in overload as their coils are on the rotor, limiting the ability to dissipate heat. However, I've not heard of this motor mfr, so perhaps it's built for sustained overloading. And there's always liquid cooling!

And I sure hope there's some fusing and circuit protection that is simply not shown in the pictures!

The 153hp is the product of 144,000 watts * .80 efficiency factor of motor = 115,200 watts to motor / 750 watts/hp = 153.6hp

I have a forced air cooling setup not shown, several hundred cfm of airflow ducted through the motor, brushes first. Even after many sustained 1000 motor amp bursts the motor feels only warm, with the "exhaust" air pretty toasty.  Forced air cooling allows a continuous power output close to that of the motor's peak.

This is besides the point though, how much power do you really need to move a car? I can roast the tires at will, accelerate faster than any car I've ever been in, and maintain a reasonable cruising speed on the highway. The motor is not a limiting factor.

There are redundant semiconductor fuses as well as a manual emergency disconnect not shown.

[Champ]

Great work!

[Soup DeVille]

I almost want to ask why you bothered retaining the transmission?

[deesea]

wait he said it'llbe in 1st and 2nd only, what about reverse?

[Soup DeVille]

wait he said it'llbe in 1st and 2nd only, what about reverse?

He'll reverse the motor instead most likely.

[GoCougs]

The 153hp is the product of 144,000 watts * .80 efficiency factor of motor = 115,200 watts to motor / 750 watts/hp = 153.6hp

I have a forced air cooling setup not shown, several hundred cfm of airflow ducted through the motor, brushes first. Even after many sustained 1000 motor amp bursts the motor feels only warm, with the "exhaust" air pretty toasty.  Forced air cooling allows a continuous power output close to that of the motor's peak.

This is besides the point though, how much power do you really need to move a car? I can roast the tires at will, accelerate faster than any car I've ever been in, and maintain a reasonable cruising speed on the highway. The motor is not a limiting factor.

There are redundant semiconductor fuses as well as a manual emergency disconnect not shown.

After reading a few of my posts it sounds like I was picking and poking. That wasn't my intent. It sounds like a very cool project.

But, as to your question, more power the better! If I were you (and perhaps you have done this), I'd mount a thermocouple as close to the rotor as possible so as to monitor motor heating. I've burned up a few motors in my time by assuming I could rely on case temperature alone.

It's good to see protection - I've seen a few low riders and the like with virtually none - they were little more than plasma bombs on wheels.

[AmpEater]

I almost want to ask why you bothered retaining the transmission?

Good question, originally I intended to go direct drive but it added too much complication. The real problem was that the driveshaft is set up such that there is a slip yoke on the transmission end. There is no easy way to adapt this to the shaft of the motor. I called many different specialty driveshaft shops and none of them thought they'd be able to fabricate what I need for a reasonable cost. The transmission was there, it worked, and it already mated to the differential so the task of mating the motor to the input shaft of the motor was much simpler. Since I've driven it in this configuration I've decided it was the way to go, I can drive it as though it were direct drive by putting it into 3rd and I can see that it pulls a huge amount more current to achieve the same acceleration, putting alot more stress on the motor and controller. Plus, direct drive would have required a much more complex wiring scheme for motor reversing, made even more difficult by the fact that the motor would be hidden in the transmission tunnel and much more difficult to wire, install, access, etc. 

I have seen a huge range of figures for the efficiency of a transmission, anywhere from 5% loss to 20% loss is quoted. If its closer to 5%, no big deal, probably saves more than that by allowing me to keep the motor in the most efficient rpm range...but if it turns out to be on the 20% side I may have to reconsider. Any hard data on this?

[Soup DeVille]

Good question, originally I intended to go direct drive but it added too much complication. The real problem was that the driveshaft is set up such that there is a slip yoke on the transmission end. There is no easy way to adapt this to the shaft of the motor. I called many different specialty driveshaft shops and none of them thought they'd be able to fabricate what I need for a reasonable cost. The transmission was there, it worked, and it already mated to the differential so the task of mating the motor to the input shaft of the motor was much simpler. Since I've driven it in this configuration I've decided it was the way to go, I can drive it as though it were direct drive by putting it into 3rd and I can see that it pulls a huge amount more current to achieve the same acceleration, putting alot more stress on the motor and controller. Plus, direct drive would have required a much more complex wiring scheme for motor reversing, made even more difficult by the fact that the motor would be hidden in the transmission tunnel and much more difficult to wire, install, access, etc. 

I have seen a huge range of figures for the efficiency of a transmission, anywhere from 5% loss to 20% loss is quoted. If its closer to 5%, no big deal, probably saves more than that by allowing me to keep the motor in the most efficient rpm range...but if it turns out to be on the 20% side I may have to reconsider. Any hard data on this?

Did you look at what it would take to mate the motor directly to the differential and bypass the entire thing? Or is there simply not enough room for that?

Anyways, I have to think that transmission related losses vary greatly from gearbox to gearbox.

At my work here, we are slowly replacing all the large DC-drive equipment with AC motors, so there's a shelf full of DC motors that nobody knows exactly what to do with. I was thinking about such a project (yeah, like I have the time!), and had thought that it would be relatively simple to mate a motor directly to the differential.

[AmpEater]

Did you look at what it would take to mate the motor directly to the differential and bypass the entire thing? Or is there simply not enough room for that?

Anyways, I have to think that transmission related losses vary greatly from gearbox to gearbox.

At my work here, we are slowly replacing all the large DC-drive equipment with AC motors, so there's a shelf full of DC motors that nobody knows exactly what to do with. I was thinking about such a project (yeah, like I have the time!), and had thought that it would be relatively simple to mate a motor directly to the differential.

That would be ideal, but just not practical in the datsun. The transmission tunnel narrows to just a few inches wide right at the mounting flange. One idea I'm still kicking around (I have a 2nd datsun, a 280z that I'm going to convert too) is to turn the differential around so it is facing the rear of the car and mount the motor where the gas tank would have been. The problem then is the differential mounts would have to be totally re-engineered, but it is doable. 

What I wouldn't give for a shelf full of motors! Go for it! The motor is about 1/5 the total cost of such a project, so you're starting out ahead of the game.

PS - Motor donations will be gladly accepted :)

[Soup DeVille]

That would be ideal, but just not practical in the datsun. The transmission tunnel narrows to just a few inches wide right at the mounting flange. One idea I'm still kicking around (I have a 2nd datsun, a 280z that I'm going to convert too) is to turn the differential around so it is facing the rear of the car and mount the motor where the gas tank would have been. The problem then is the differential mounts would have to be totally re-engineered, but it is doable. 

What I wouldn't give for a shelf full of motors! Go for it! The motor is about 1/5 the total cost of such a project, so you're starting out ahead of the game.

PS - Motor donations will be gladly accepted :)

Yeah, so far it's just been idle imaginin'. I alreeady have two ongoing projects that are nearly stalled for lack of time to work on them.

Understand, those motors aren't exactly mine at this point. Someday, I expect they will be "red-tagged" and moved to the scrap bins; and I'll have no problem claiming any of them once that happens.