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Old 06-28-2016, 12:43 AM   #11 (permalink)
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Originally Posted by RedDevil View Post
I read about this project.
IIRC they found they could accelerate faster by carefully controlling the speed of the wheels to some precalculated rate rather than relying on traditional traction control, so they could operate on the limit all the time.
TC would take it slightly over the limit, then fall back behind to regain the correct speed.
That makes a whole lot of sense.

And with the electric motors, they can control the exact rate of wheelspin, so even if they lose traction, they still get linear acceleration.

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Old 06-28-2016, 03:12 AM   #12 (permalink)
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Here is something some of you might find interesting.

It's an article by one of the engineers at the company that supplied the laminations for the motor. In the article are some performance graphs and cad drawings of the motor. Oh - also some FEA analysis showing some very impressive flux densities...

Pushing the envelope for electric motors | EETE Automotive

- Enjoy!

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Old 06-28-2016, 03:42 AM   #13 (permalink)
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Quote:
Originally Posted by niky View Post
That makes a whole lot of sense.

And with the electric motors, they can control the exact rate of wheelspin, so even if they lose traction, they still get linear acceleration.
That's why they regulate speed rather than torque.
Torque monitoring (alone) is not optimal as the slightest bump in the road will generate a variance in how much torque you can apply.
By keeping the speed stable a momentary loss of traction will not cause a slipping wheel.

TC works by bringing the speed of the wheel back in line with the others.
No need for that if the speed of all wheels is the same to begin with.

As the weight transfers from the front to the back the front wheels get less grip while the rears get more. But all of them need to turn at the same speed.

That said, if they overdo the speed buildup all 4 wheels will lose grip and the thing does a 4 wheel burnout.
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Old 06-28-2016, 05:32 AM   #14 (permalink)
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Quote:
Originally Posted by RedDevil View Post
That's why they regulate speed rather than torque.
Torque monitoring (alone) is not optimal as the slightest bump in the road will generate a variance in how much torque you can apply.
By keeping the speed stable a momentary loss of traction will not cause a slipping wheel.

TC works by bringing the speed of the wheel back in line with the others.
No need for that if the speed of all wheels is the same to begin with.

As the weight transfers from the front to the back the front wheels get less grip while the rears get more. But all of them need to turn at the same speed.

That said, if they overdo the speed buildup all 4 wheels will lose grip and the thing does a 4 wheel burnout.
I'm pretty sure everything is measured against a time delta... possibly the wheels will not accelerate faster (or probably more than x% faster) than the car can.

Buuuuut... if you give the car a GPS speedometer, or maybe even an inertial one... the controller can correct wheel speed to adjust for slippage on the fly. I doubt that's what they're doing here... but it's a fascinating thought (like the GPS-aware gearshift on the Rolls Royce Wraith that predicts upcoming corners)

Parts of the video show the car doing donuts, which shows that yes, what you posited actually can happen.
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Old 06-28-2016, 02:13 PM   #15 (permalink)
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Originally Posted by niky View Post
And with the electric motors, they can control the exact rate of wheelspin, so even if they lose traction, they still get linear acceleration.
Not much. Ever tried to accelerate on ice by stomping on the gas?

So that's my open-minded question. There is no fundamental problem getting electric motors to apply as much force as desired - even, as with the rail gun, far more than the car's structure could withstand, let alone a human body. But how do you get tires to apply enough force to the road to accelerate at that rate, instead of just sitting there burning rubber?
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Old 06-28-2016, 03:34 PM   #16 (permalink)
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Possible, with traction as the limitation?

Well, it's been done quite a few times before.

Here's the "White Zombie" - a converted 1972 Datsun pulling sub 2 second 1-60's.
Electric White Zombie Claimed to Do 0 to 60 MPH Dash in 1.7 Seconds (w/video) - Inside EVs
Welcome to Plasma Boy Racing, home of White Zombie, the world's quickest street legal electric door slammer in the 1/4 mile drag.

Here's "Killacycle" (I've seen it in person) doing close to 1 second 0-60. Somehow, the bike and rider have survived AND the rider has managed to hang on.


There's some seriously fun stuff out there - have fun!!
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Old 06-29-2016, 02:51 AM   #17 (permalink)
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Originally Posted by jamesqf View Post
Not much. Ever tried to accelerate on ice by stomping on the gas?

So that's my open-minded question. There is no fundamental problem getting electric motors to apply as much force as desired - even, as with the rail gun, far more than the car's structure could withstand, let alone a human body. But how do you get tires to apply enough force to the road to accelerate at that rate, instead of just sitting there burning rubber?
They're using slicks, from what I can tell, and they're using warmer blankets to keep them at the right temperature and stickiness.

After that, it's all about knowing how much grip they have and adjusting the controller accordingly.

And the ice thing, that can be dealt with via an inertial/GPS traction control system. It still won't accelerate quickly, but you can fine-tune wheel acceleration rates so that you're not needlessly spinning them up.
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Old 06-29-2016, 02:33 PM   #18 (permalink)
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Quote:
Originally Posted by niky View Post
After that, it's all about knowing how much grip they have and adjusting the controller accordingly.
Sure, the question is what the heck are they using that has sufficient grip?

Quote:
And the ice thing, that can be dealt with via an inertial/GPS traction control system. It still won't accelerate quickly, but you can fine-tune wheel acceleration rates so that you're not needlessly spinning them up.
Yes, to a degree, but even if it's done perfectly, the acceleration will be slow (if it happens at all), simply because there isn't enough grip between tire & ice.
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Old 06-29-2016, 03:04 PM   #19 (permalink)
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Quote:
Originally Posted by e*clipse View Post
Possible, with traction as the limitation?

Well, it's been done quite a few times before.
Thank you for finally bringing the White Zombie and Killacycle into this thread. The Zombie did 1.6 second 60 foot runs six years ago with nothing more than a calibrated right foot! That was with street legal tires, no warming blankets or any nonsense other than a burnout. Sure, advanced controls can both win races and improve safety, efficiency, and repeatability, but it's just to replace driver skill and govern the brute force inherent to electric drive. I enjoy regen EVen more than the next guy, and may never buy another pure ICE vehicle, but it's still my series-motored conversions that give the biggest EV grins.

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