# what's the next step?



## DavidDymaxion (Dec 1, 2008)

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.


2cycle said:


> 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.


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## 2cycle (Jul 2, 2009)

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)?


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## major (Apr 4, 2008)

2cycle said:


> Just for comparison sake, how much horsepower does a off the shelf 100 lb DC motor produce (60 min. rating)?


I'd say about 20.

For a liquid cooled AC motor, maybe 100.

Controller and cooling system not included in the 100 lbs.


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## DavidDymaxion (Dec 1, 2008)

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).


2cycle said:


> 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)?


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## 2cycle (Jul 2, 2009)

When I worked for Arctic Cat the dyno operators that tested durability would make 60 minute runs at full throttle at peak hp rpm. If all goes well they just have to keep feeding the fuel tanks. 
The snowmobile world uses 180 hp 2 stroke engines that weigh in near 90 lbs and they can run for at least 60 min on 91 oct pump gas. This is the stock engine configuration. Now the modified versions with turbo charging (not OEM) can produce 480 hp in the same 90 lb package (+turbo wt) and that is good for drag racing and speed runs, but when tuned properly will last a season of racing.

This is my dilemma. I'm soo use to light weight engines and fuel cells that it's very hard for me to build an apples to apples performance vehicle. You guys talk about 500 lbs of motor and batteries like it's normal. A 400 hp race snowmobile only weighs 500 lbs total. 
I guess if I were a car guy then it would compare favorably for the electric conversion, but I'm not and this is frustrating for me. I want to build something electric in the worst way, and on a customers dime not mine , but I can't seem to find the right project for the available parts. Roadrace vehicles are as good as any place to start with because they don't have crazy hp so it's a better match for EV. I'm more into terrain racing were weight is a huge penalty, and I like drag racing were hp rules the roost.


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## major (Apr 4, 2008)

2cycle said:


> 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.


Hi 2cyc,

Yeah, ya never know what's around the corner. But I doubt seriously it will be a better brushed DC motor. The basic design there is 100 years old. We have some better insulation and run them hotter for increased power density. Maybe some better alloy steel and process to make them a little more efficient and cost effective. But the copper, steel and carbon aren't that much different in all this time. You see these insane power figures because these guys overload the crap out of them. Amazes me that they live as long as they do, like what 10 to 15 seconds? Try sustaining that power level for a 10 lap race 

So where the EV motor is going is where it is in the EVs and HEVs being produced today. AC. Some ACIM and some PMSM. Active thermal management. Good efficiency. Reasonable power density. Cost effective. Able to be validated for automotive. What more could the consumer want? And you know what? They are not much different from the EV1 motor circa 1995 

You seem to think there is some sort of traction motor industry. Speaking about the EV car motors, I do not see a traction motor industry. Auto makers will likely make electric motors themselves, like they do engines, or have selected vendors do it, like Remy. And yes, these guys have R&D departments. And undoubtedly are busy working on better motors. But I don't see the "Lithium" motor around the corner. You have the switched reluctance motor. Only been around for 30 years. And that technology has seemed to merge with the PMSM to give a motor with magnet torque and reluctance torque, so to speak. A pure reluctance motor? Yeah, maybe, F1 KERS was using that I heard. Like 60 kW at 50,000 RPM in a soup can size package. Got gears for that? And you think you could find a place to buy one without an F1 budget 

And then you have this whole thing about wheel motor. I suspect we'll continue to see wasted effort on this idea  Can't stop it. 

A guy like you wants to get a high power dense motor to race with. You just need to get the best available from automotive and push the crap out of it. Or find some other source for a core and develop it. This takes a commitment of money which nobody is willing to make. They all want guaranteed success with payback next year. We need somebody who doesn't mind 10 or 20 failed attempts. And who could tolerate the prospect of never seeing a return on money spent. Somebody in it for the chase, not the pot of gold.

I know of a few who are engaged in trying some different things with motors. Axial air gap (pancake) designs. Ironless armatures. These are interesting. But nothing I haven't seen years ago. Maybe with better materials they can further push limits on speed and make some incremental gains. Kudos to these guys. Keep after it.

But for you, I don't see a better motor tomorrow. Like I said, get the best you can find and push like crazy. Break it and fix it better. Repeat. And again. That's the way your IC race engines got to where they are, isn't it? And along the way, you might invent the turbomagneticultraconducting gizmo 

major


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## toddshotrods (Feb 10, 2009)

Your best bet for anything anywhere near your two-cycles is AC, and the first major hurdle is going to be the inverter - if you can find a motor. High-rpm horsepower isn't really the DC series motor's forte. AC on the other hand can spin crazy numbers, and if your vehicle is 500lbs total you don't exactly need stump pulling bottom-end torque. Who are you going to get to build a 500hp inverter though.

Second hurdle is a pack light enough to get you even close to the ICE engine and fuel cell. The best lithium packs (pouches) don't have that kind of power density - yet.

The point is you have to be willing to do what Major suggested: start developing on your own, and be at the forefront when it comes of age. Or, wait until someone else does and join the party. It's just all too green (pun intended) and new right now.

The hard truth that people don't seem to like to swallow is electric is still slower than ICE. It's gaining fast, but not quite there yet. Dollar for dollar you will cross the finish line _after_ a comparable ICE. My race rod, with the current plan, will be around the same weight as it would have been with an all-aluminum ICE V8 (that cost as much as my battery pack will). It will be about a second slower, with the absolute best battery pack obtainable. I don't expect the ICE vehicles to wait for me to catch up.


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## 2cycle (Jul 2, 2009)

good info guys, and I tend to believe the time spent on wheel motors is kind of useless myself. There are so many variables that don't lend themselves well to wheel motors for production vehicles. The only wheel motor driven vehicles that make sense to me are mining trucks.
Major, I can imagine the EV1 motor your using has got to be a pretty nice quality piece. I agree with you that AC or some variation of it is likely going to be my style of motor to meet weight demands. 
I think part of my problem is trying to grasp what is maxed out and what is not. With ICEngines there's always something you can add or inject or modify to take it another step. I think I was hoping there were those same types of stage tuning/building one could do with a traction motor, AC and DC. It appears the structure of them is well built and doesn't allow for much altering for better performance, yet anyway. 
I hope to have my dyno built by end of winter and maybe that will be my best test time. If all goes well then putting it to use in a drag sled or ATV would be my next step.
Todd, I've come to realize the good hp comes from high voltage and monster packs, which don't work too well on a snowmobile, better than a motorcycle but still only so much room to work with. The nice thing with sleds is the width where the motor sits, it's around 34", so 2 motors end for end is doable. 
I just have lots of possible scenarios and can't seem to chose just one.
And yes we don't need much low rpm torque in a light weight vehicle because we will just spin off the line anyway, plus we use CVT so a nice power peak is what's needed. We really can't get much quicker than we already are. If you look at Zombie's timeslips you can see his 60' times of 1.6's , we are in the 1.2's and on the well prepped tracks 1.1's, yes that means that after 1 second or so we would be so far ahead of zombie he wouldn't believe he's getting whopped by an overgrown weed eater built like a tank. The usual response to seeing a sled run 160+ mph in the 1/4 mile is "what the he-- was that".


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## resago (Sep 28, 2010)

what about these binary motors they are putting in toys these days, the mini helicopters and such, they have way more power than the motors I played with as a kid, (20 years ago). The motors I see in EV are the old tech. can these binary motors be scaled up?


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## DIYguy (Sep 18, 2008)

2cycle said:


> If you look at Zombie's timeslips you can see his 60' times of 1.6's , we are in the 1.2's and on the well prepped tracks 1.1's, yes that means that after 1 second or so we would be so far ahead of zombie he wouldn't believe he's getting whopped by an overgrown weed eater built like a tank. The usual response to seeing a sled run 160+ mph in the 1/4 mile is "what the he-- was that".


The Zombie weighs over 2300 lbs also, I believe. How would the sleds look lined up with the Killacycle... a little more comparable weight? I think it's 60mph times are under 1 second... not sure about 60 ft.


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## major (Apr 4, 2008)

resago said:


> what about these binary motors they are putting in toys these days, the mini helicopters and such, they have way more power than the motors I played with as a kid, (20 years ago). The motors I see in EV are the old tech. can these binary motors be scaled up?


Sorry, I don't play with little toys much anymore  What is a binary motor?


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## 2cycle (Jul 2, 2009)

DIYguy said:


> The Zombie weighs over 2300 lbs also, I believe. How would the sleds look lined up with the Killacycle... a little more comparable weight? I think it's 60mph times are under 1 second... not sure about 60 ft.


Actually very close to the sleds that actually use sled engines to start with. The outlaw sleds with dual engines and such can't compete at NHRA or IHRA tracks because of safety rules, but the more normal (safer) sleds are in that same area of 7.80's and 170ish mph, I think the record is 7.70's @180ish right now. The sleds also weigh about the same as the killacycle.
The biggest difference is the big heavy track and not tires. The snowmobiles that I speak of are over 500 hp at the crankshaft but they lose so much hp turning a track that they suffer speed as well as not as good traction off the line compared to tires. When you put snowmobiles on an ice track where they belong only a top fuel bike can compare to the acceleration of an open mod sled with picks in the ice.


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## 2cycle (Jul 2, 2009)

major said:


> Sorry, I don't play with little toys much anymore  What is a binary motor?


don't the RC toys use brushless DC motors?


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## DavidDymaxion (Dec 1, 2008)

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).


2cycle said:


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


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## resago (Sep 28, 2010)

acuatlly i was thinking of a digital motor.

there also the dyson thing:
"
The Dyson Digital motor, code named X020, is a 100,000 rpm switched reluctance (SR) motor, meaning that the reluctance (magnetic resistance) is switched between the pole of the stator to create torque through the rotor, forcing it to spin. The motor spins at more than five times faster than a Formula One engine (19,000 rpm), while typical vacuum motors run between 30,000 rpm and 40,000 rpm. It lasts twice as long as conventional motors because of several factors, including no carbon brushes or commutator. 
Dyson’s motor has copper windings on the stator only, which have been overmolded to increase reliability. Conventional brushed motors – the typical motor used in vacuum cleaners – have copper windings on the stator and rotor. Because of the windings being on the stationary part only, the SR motor is more reliable than conventional motors as they have exposed windings on the rotating shaft assembly that are prone to damage."


have a look at one of the toy helicopters that cost around $50 and tell me which kind of motor it is.


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## DawidvC (Feb 14, 2010)

http://www.plettenberg-motoren.com/UK/Motoren/aussen/Predator37/motor.htm

This motor delivers 15kw in a 1.9kg (4pnd) package. It needs to be upscaled, but if it is possible to do, you should get 300kw(400hp) nominal, 600kw peak in a 38kg (80pound) package

I doubt if it is possible to actually do the scaling, but it can be interesting to try.

Dawid


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## DawidvC (Feb 14, 2010)

Sorry about posting twice, but I was typing faster than I was thinking.

If you use this type motor @ 150kw, it will be approx. 40lbs. Add 75lbs for a pack similar to Killacycle, and another 40lbs for the controller, the whole propulsion system will be approx 160lbs for 200hp cont, 400hp peak.

Now we just need to find a sponsor 

Dawid


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## toddshotrods (Feb 10, 2009)

DavidDymaxion said:


> ...The new Killacycle pack is 75 lbs (yes, seventy-five!) and delivers 500 hp!...


Any more details available? A123 again or new sponsor? Composition? Numbers (amps and voltage)?

*Edit =* Did some Googling - very interesting...

Read the post from Sept 30th...

About halfway down this page...


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## DawidvC (Feb 14, 2010)

Thanks for the info on killacycle, Todd. It means that for a bit over 200lbs you should be able to squeeze out 800hp, or else have 400hp for less than 140lbs. Interesting .

BTW, except for the fact that neither the motor nor controller has been designed, we are still talking todays technology. No superconductor or exotic material needed.

Dawid


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## toddshotrods (Feb 10, 2009)

DawidvC said:


> Thanks for the info on killacycle, Todd. It means that for a bit over 200lbs you should be able to squeeze out 800hp, or else have 400hp for less than 140lbs. Interesting .
> 
> BTW, except for the fact that neither the motor nor controller has been designed, we are still talking todays technology. No superconductor or exotic material needed.
> 
> Dawid


You can't even consider those cells, unless you have sponsorship, or happen to be incredibly wealthy. The fact that they're mad efor F1 cars, and have such high power density, means the price would be beyond astronomical. I know some guys who build seven figure (that's not a typo) hot rods and race cars, and that may even be out of their budget.

It does hint at what might be coming our way someday. The cells, like A123 M1s and Kokams, that we think are so hot today were unheard fo not so long ago...


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## major (Apr 4, 2008)

DawidvC said:


> http://www.plettenberg-motoren.com/UK/Motoren/aussen/Predator37/motor.htm
> 
> This motor delivers 15kw in a 1.9kg (4pnd) package.


I wonder how you connect the three 2/0 cables to it


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## 2cycle (Jul 2, 2009)

So killacycle has more hp than Zombie?


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## DavidDymaxion (Dec 1, 2008)

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.


2cycle said:


> So killacycle has more hp than Zombie?


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## 2cycle (Jul 2, 2009)

DavidDymaxion said:


> 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.


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.


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## major (Apr 4, 2008)

DawidvC said:


> If you use this type motor @ 150kw, it will be approx. 40lbs. Add 75lbs for a pack similar to Killacycle, and another 40lbs for the controller, the whole propulsion system will be approx 160lbs for 200hp cont, 400hp peak.


Hi Dawid,

I'm not sure if you are serious here or not. First you jump to a conclusion about doubling stated power to get peak of 400hp. And do you really think the little motor can be scaled up by a factor of ten? I guess you could just use ten of the little guys. But how much of that 15 kW apiece will be required for cooling air over and thru the motor? Be interesting to try. They were about 1000 euros apiece. And then again for a controller. About ripe for a go kart, wouldn't you say?

I have to wonder a bit about these hobby/model motors and equipment. They have made great strides recently with the availability of LiPo batteries. But I just recieved a Tower Hobbies catalog today and was looking at ESCs (electronic speed controllers). They have a TL2522 listed at $149, 1.36 oz, 1620 amperes rated. For brushed motors. 

Regards,

major


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## DavidDymaxion (Dec 1, 2008)

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


2cycle said:


> 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.


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## Bowser330 (Jun 15, 2008)

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?


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## toddshotrods (Feb 10, 2009)

With all this in mind, and getting back to the main subject for this thread, I think the next big step for EV drag racing is going to be purpose-built motors. Right now battery packs are the limiting factor. Even though they are available now, you have to be sponsored, wealthy, or single (read, free to "waste" as much money as you please - like me), to afford to experience it. When that changes and more people have access to serious power, the motors are going to become the weak link. Also, as battery technology advances, the sponsored, wealthy, and single, are going to push existing motors way beyond their physical limits.

Right now the solutions are a bunch of subtle improvements and some not-so-subtle band-aids. If you go back and look at ICE drag racing you will actually see a lot of similarities, including the use of dual (and triple and quad) motors to get more power; and borrowed and modded factory parts. Eventually, purpose-built racing parts, and even full engines, replaced all that and now we have 8000hp T/F and F/C.

If Jim doesn't have any real secrets inside those motors, someone eventually will. If he does, they will eventually be discovered by others and competition will drive advancement. When I started racing motorcycles Vance & Hines had secrets inside the cylinder heads that allowed them to totally dominant the rest of the field. Now, there are others who can compete head-to-head with Byron Hines' porting work, and there is a healthy, competitive, sport.

I really have no idea what I'm talking about but my instincts tell me that custom winding is the key to massive power in the future. Every one is afraid to even consider it right now, because the motors haven't reached their physical limits yet. Time-consuming yes, but time is money and racing ain't cheap...


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## DavidDymaxion (Dec 1, 2008)

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.


Bowser330 said:


> 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...
> 
> ...


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## Tesseract (Sep 27, 2008)

DavidDymaxion said:


> 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.


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...


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## DavidDymaxion (Dec 1, 2008)

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.


Tesseract said:


> 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...


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## GerhardRP (Nov 17, 2009)

Tesseract said:


> 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...


I wouldn't mind giving it a shot... If I can get my hands on the Zilla dumps that went with the White Zombie's record runs. I am a physicist not planning to drag race myself. As I said before, I am sure the best gearing is that which allows a flat out motor/controller at launch to make just enough rear wheel torque that the tires barely slip.
Gerhard


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## 2cycle (Jul 2, 2009)

You don't have to figure it out if your controller can sample rpm quick enough to plot it against time and not let the rpm increase faster than a predetermined rate which takes a few passes to set a base line. We can do this with ICE using the ignition to limit power off the line to control wheel/track spin. The rules against traction control are for active systems such as this and NHRA doesn't allow it so be careful. I believe using this acceleration limiter approach is the best way to do it but is the most looked at by NHRA as well. 
I would think this would be very easy to do with an electric motor seeing it's so easy to do with ICE.


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## E4mula (Mar 31, 2009)

There would be a lot of variables to set up a physics based algorithm for launch control; track prep/temperature, tire temperature, etc.. that could change on each run. Better to let the processor in the controller handle the dynamics.
You could set up a ramped acceleration rate like 2cycle suggested which would be great for consistency in bracket racing, but not if you're trying to set new time records or to run at the traction limit.
Setting up a drag racing launch control routine wouldn't be too difficult. Class rules at the track may disallow it though.


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