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Author Topic: Opening the throttle -> losing control?  (Read 3706 times)

clay.leihy

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Re: Opening the throttle -> losing control?
« Reply #45 on: October 22, 2016, 02:30:23 PM »

This is a common misconception. Motor RPM in an ICE is NOT equivalent to Wheel RPM.

I didn't say it was. That's what gearing achieves, in fact it's very much the point.

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Meanwhile, the zero is phase amp limited. Until your motor RPMs increase, it doesnt make 100% power.

Nope. The controller's current limit is the HIGHEST limit on an electric motor. At higher speeds, the inductance of the motor windings reduces the peak current available, which reduces the torque output of the motor. Look it up. Highest torque at 0 rpm, pretty much flat until field weakening kicks in at some rpm, ramping down smoothly to zero. Keep in mind that this is not a simple synchronous AC motor like in your refrigerator. Topologically, it's closer to a brushless DC motor, and driven by some very smart electronics.

Which brings up perhaps the biggest mistake you're making, which it seems like you've always made in your posts. You're conflating torque and power, which are very different things. Torque is the ability to accelerate a vehicle; power is the ability to dump energy into a system quickly. It's the difference between a "power lifter", whose immense strength allows him to (fairly slowly) bench press hundreds of pounds, versus a hammer thrower, who doesn't have the ultimate strength of the weightlifter, but can supply energy into a heavy weight much more quickly to throw it a much longer distance. Torque is an earth mover; power is a Formula 1 car. When and if you understand the difference between torque and power, you'll be much closer to understanding vehicle performance. A drag racer needs torque; a NASCAR car needs horsepower.

Okay, you have a minor point concerning transient conditions (fanning the clutch to rev the motor, etc.), but overall, it's about torque at low speed, power at high speed.

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Top fuel dragsters all the way down to Gokarts, powerboats, planes, anything where the output is not dependent on engine RPM and will allow for an idle, so tons of hydraulic couplings on most things.

I was referring to commercially available cars and motorcycles, but okay, another minor point conceded. BUT I was also saying the engine cannot run at 0 rpm, and that's absolutely true for an ICE. You can decouple it from the wheels to keep it running, but the motor's not at 0 rpm when you do that. You also seem to have a habit of conflating rpm (engine speed) with road speed, even though you yourself made the point that they're not the same thing.

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But I have to wonder about the accuracy of the statement. A manual transmission is not heavy. They are not expensive in mass production, This application requires no clutch, They use very little oil or other lubrication, and can be made with 100,000 mile service intervals. Modern designs dont leak, and they rarely require servicing.

C'mon man...however cleverly they're engineered, they're bulkier, heavier, less efficient, more expensive, and require more service than nothing. What exactly are you trying to argue here?

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The busa goes faster than 90mph in 1st gear. so your performance off the line would remain insane, and it would continue until you hit the 11k redline.  Clearly not the bike to compare it to.
The zero motor makes similar torque to a literbike AT THE CRANK, but it literally is doing what you say above.. it is starting out in roughly 3.5 gear compared to the literbike sportbikes.

All modern literbikes can exceed 90mph in first gear with their stock gearing. They also all redline around 13,000 RPM.
The ICE motorcycles have their torque multiplied by almost twice what Zero does. Its no wonder they're so much faster.
If you regeared a zero to the same rear wheel torque level (besides having a rear cog larger than the tire) you would be just as quick, but only go 45mph. (when fully charged.)

The power is there, but how its transmitted to the ground is very far from ideal for a performance or efficiency application. The reason ICE motorcycles have multiple gears is not lack of power.. its to lower RPM for efficiency and sanity. The vibration is nuts. Its too loud.. etc.

*Sigh* Yes, one of the reasons ICE motorcycles have multiple gears is because you can't run them at high rpm all day. It's hard on the equipment and very inefficient. But they also need gearing because they don't make torque down low. If they did, you could simply put a single gear on the 'Busa, geared for max speed, and drive it around that way, exactly the way Zero does. If you tried that with a 'Busa, let alone an SV650, it would be an awful (if even possible) riding experience. But it works out very well on the Zero, because the Zero has enough torque down low to pull a fairly high gear right from 0 mph.
I can walk my Zero up the 45 degree slope up to the back yard of my townhouse with a tiny bit of throttle. Try that with an ICE. Oh, I have, and it's a real pain revving it high enough to make the torque to get it up the hill and harder to control as well.

Sent from my Z981 using Tapatalk

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Clay
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Alan Stewart

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Re: Opening the throttle -> losing control?
« Reply #46 on: October 23, 2016, 07:00:51 AM »

Amen. It's not just Lightning, either. Tesla does 0-60 quicker than any other commercially available car, including hypercars, with a single gear that tops out at 150 mph. The motors that provide that level of performance are roughly the size of a watermelon, weighing a couple hundred pounds. This is a luxury car produced for the mass market, not a one-off sports car. Still not enough for you? How about Killacycle? If 0-60 in 0.9 seconds isn't quick enough for you, or its top speed of well over 150 mph isn't fast enough for you, you really need to seek professional help.

Doubly impressive is that the Tesla Model S P100D is most certainly far heavier than any of the cars it's being raced against. Drag Times recently discovered that even in the wet it still does 0-60 in 2.7 seconds, only 0.2 slower than in the dry. Part of the reason is AWD. Maybe what we need is a 2WD Zero SR. 😁
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Alan
2018 Tesla Model 3 LR
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