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Old 12-31-2008, 10:50 PM   #30 (permalink)
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I don't necessarily agree w/the issue about 1:1 coupling w/ the wheels, only b/c if you read back through bennelson's E-metro build - he has a video taking off in 3rd and 4th gears, working up to 30mph in 13 seconds each time...

Those two gears are as close to 1:1 as most transmissions will get, and having both of them showing the same acceleration curve shows that the relative torque output of the engine (which most certainly ISN'T 27 HP, being from a forklift which has insane reduction in the transaxle) is more than enough to move the car.

I'm sure that what actually would happen in this case is that even though the 4x27 car might accelerate something comparable to a Corvette (I dunno about this one either.), it will also use more amps to get to speed being directly coupled with no option for gear reduction or changeable speeds.

The Tesla uses a 14krpm AC motor coupled to a single speed gearbox... but if you look at the "dyno" info for the tesla's motor, it develops and MAINTAINS a plateau of peak TQ from 0-6krpm.. while any other car is having to build up that torque to get moving, an e-car already has it, which means that coupling it 1:1 even on a take off would have an ICE power equivalent of launching a 1:1 (final) ratio gear at peak TQ in the RPM range.

Now, I wait for someone to call me out for not mentioning that tires technically change final drive ratio to a greatly underdriven ratio.

Frankly, I still don't think that the e-motor would have much trouble taking off, coupled exactly 1:1 with a wheel/tire combo of reasonable size compared to the power output of the motor. 27HP is more than enough to move an average 13" tire and make it accelerate decently.
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