[DavidDymaxion]

Are DC motors really too heavy? My DC motor is 1/3 the weight of the gas motor and accessories it replaced, yet EV drag racers have run 2x the hp and 3x the torque of the gas motor (I'm modestly only going for the same hp.). That's about 6x the hp per pound of motor! You would be very hard pressed to get the 2.7 L gas motor up to 3000 hp to have the same motor power/weight ratio!

Don't forget the DC motor includes a mechanical inverter (the commutator). If you take the weight of a DC motor plus controller, the weight is similar to an AC motor and controller (where the inverter is in the controller rather than the motor).

The heavy case of an electric motor provides a magnetic circuit path. An EV drag racer tried to save weight by machining away some of that heavy metal -- he went slower! That effectively put resistance in the magnetic circuit.

So I wouldn't wait for any "next generation" motors -- electric motors are a pretty mature technology -- we have great motors available today! I think research money would be better spent improving battery technology.

It seems like the style of traction motors available haven't changed much over the past 10 years. I can't imagine there's not a new design coming down the line. What is the next big change in design, anybody know? In my opinion the weight has to be the biggest hurdle to overcome. DC motors weigh too much in my mind. The question is can they be re-engineered with lighter components that maintain the same energy as the current components?
I see this same problem in current auto engines. The tech is there to produce lighter assemblies yet they haven't had a good enough reason to force their hand into using it yet. Oil is still too easy to get so the extra weight of the vehicle can be overcome by more power but at an expense of efficiency.

Does the traction motor industry need a large sum of money to get things started? Is there any pressure being put on them yet? Maybe there is a lot more going on than what we see from our view. Do you suppose the traction motor companies already have a good head start but their not showing their hand just yet? I've read on here about companies that have a product but they don't sell to individuals, which seems counter productive to me.
Anyway I'm just thinking through my fingers. It sure would be nice to know what's around the corner.

 

[DavidDymaxion]

The 60 minute thing is a spec for electric motors that run extended times, and not really an apples-to-apples metric for comparing to gasoline engines. Open Road racing has shown that many high performance motors are not up to full horsepower for 60 minutes. For that matter, many cars are not up to track use, where for an overall average you are only 1/2 power, they'll still overheat. My gas car, for instance, is overheating by the end of a 20 minute track session, even though the gauge never budges off a low temperature otherwise.

Part 2 is look at how monstrous the cooling system is on a typical ICE, vs. virtually nothing for an electric's cooling system.

This is a long way to say it's not directly comparable to take a typical ICE's max hp, good for a small number of minutes, compared to the 60 minute electric spec.

Now that said, John Wayland put about 400 hp through his 180 lb Kostov for drag racing. That's over 2 hp/lb. Bill Dube puts about 500hp through about 100 lbs of DC motors -- that's 5 hp/lb. That's 10 second kind of stuff. Wayland regularly destroys motors, Dube has lost at least one, but they get at least several track trips out of a motor.

I believe the Tesla does about 2 hp/lb for its motor -- it'll do the track (for a while, anyway, before it cuts back due to overheating, just like my gasser).

That was my point precisely. Auto engines weigh so much because it's cheaper to just make more hp to achieve performance goals than to use new tech and tooling to lighten them. Plus most IC engines are reciprocating machines and require much heavier construction than rotating machines so some of that weight is needed.
As my screen name implies I'm a 2 stroke gearhead. So when I'm comparing my style of engine to any other style, my beloved 2 strokes produce more hp per lb of engine weight than anything else. In my world a racing engine that lasts all season without failure can produce 1.5 to 2.0 hp/lb naturally aspirated and 4.0 hp/lb when forced induction is used. Auto engines don't really compare to these numbers and from my research neither do DC motors. I think they will some day and yes the money is well spent in the battery development world.
Just for comparison sake, how much horsepower does a off the shelf 100 lb DC motor produce (60 min. rating)?

 

[DavidDymaxion]

The Killacycle has about 100 lbs of motors. The new Killacycle pack is 75 lbs (yes, seventy-five!) and delivers 500 hp! Bill Dube says that no mere mortal could afford to buy it, though.

There was a discussion on the NEDRA list recently. A long, skinny motor will deliver more hp / lb (allows higher rpm and more surface area / kg for heat dissipation).

... You guys talk about 500 lbs of motor and batteries like it's normal. A 400 hp race snowmobile only weighs 500 lbs total. ...

 

[DavidDymaxion]

When the Zombie had a Kostov it was lead acid. With its Kokam pack it is now higher -- Wayland estimates 900+ hp! http://www.plasmaboyracing.com/blog/?p=170 . So Zombie wins in hp, but I think Killacycle still has better power/weight.

So killacycle has more hp than Zombie?

 

[DavidDymaxion]

Apologies if that was confusing -- I didn't mean to imply pack hp was what he was getting to the ground.

I agree his times are not consistent with 900 hp, but he only tuned the Zillas for 1/2 the pack's potential. His times are in the ball park for 450 pack hp. This is a fresh pack and he'll be working up in hp. He'll need some more safety equipment to go into the 9's, which he hopes to do. So, so far his motors have passed hp of around 450 hp... but hold the phone for a moment...

He did once accidentally wire something up backwards that disabled the Zillas' current limit! He estimates he might have been dumping 3000+ Amps, per how far down the very stiff batteries sagged! He said the car felt very fast. They could not get it to hook up. That might have been as much as 800 hp input to the motors! (That's my estimate, not John's, by figuring 3000 Amps and batteries sagged to the 1/2 way point.) His motors survived, but Otmar warned he likely greatly shortened his Zilla's life. I would guess the high Amp excursion was very brief, and don't forget he is running twin 9 inchers now. Ah heck, John tells the story much better, check it out it is a great read:

http://www.plasmaboyracing.com/blog/?p=239

The way I read it he stated the pack is capable of 900+ hp. His motor surely doesn't put out that kind of power because if it did he'd be a lot faster than he is. 900 hp range is what a few of my friends have in their cars and they run waaaaayy faster than WZ. 900 hp in that light of a car is 1.2's 60' and mid 5's in the 1/8 @ 120's mph without even trying. My friends car runs 4.9's in the 1/8 with 950 hp.
Anyway the WZ article also says he predicts using half that pack power will net him 10 second times, so I would say he's got around 500 hp like killacycle does.

 

[DavidDymaxion]

The Advanced DC motors can only take around 160 or 170 Volts. His leacid packs would sag so much he needed to go parallel. The new lithium pack is so stiff he decided to stay in series.

interesting....in the blog Wayland mentions running the motors in series mode exclusively, no more electronic series parallel shifting...hmmmm

this means that the motors are getting 1/2 the voltage and the full amperage form the controller...

so with a 400V pack, they would be getting 200V & 2000A from a ZillaEHV2K....

I always thought you wanted the high voltage to push the peak amps out to higher rpm...it seems as though wayland is only putting less then 200V into each of the motors...

Is it because the re-gearing is allowing him to get to 125mph trap speeds at a lower rpm and therefore still in the peak torque range of the <200V motors?

 

[DavidDymaxion]

Also you'd need to take into account it takes time for the Zilla to shift from series to parallel.

I think the optimal controller would have three main transistor switches, and gradually and continuously shift the motors from series to parallel instead of doing it in one big step.

Yup. Mind you, it's not a bad thing to stay in series... As long as you haven't run out of voltage (hit 100% duty cycle) that is.

Actually, I just know there is an optimal (physics-based) method for determining when you want to hit 100% duty cycle in the controller for a straight-shot drag race. Applying a little math here ought to do the trick... unfortunately, I've been out of school way too long to remember how...