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Old 01-06-2009, 01:36 AM   #125 (permalink)
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Join Date: Nov 2008
Location: Troy, Pa.
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Pasta - '96 Volkswagen Passat TDi
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Ok, so since we touched the subject of using voltage vs. current to propel the vehicle, I wonder if I have this correct -

If there is an increase in the voltage, there can be a subsequent decrease in the current to create the same power, however the RPM is increased accordingly.

So if at 120v 20A the motor spins 500RPM and creates 50lbft TQ, and I switch to 240V 10A, It will create the same 50lbft, but at 1000RPM?

So if I have that correct, that leads me into this: What happens when you've done this to the extent that you'd be making minimal torque at 6000RPM, but you gear down and use reduction to recreate that torque to the wheels?

If you have a motor that runs on 120VDC 20A and makes 50LBFT TQ @ 6kRPM,
Then you use 240V 10A, it should make 25LBFT TQ @ 6kRPM, right? So what if I gear it down 2:1, I get that 50LBFT back at the output, which is now traveling 3kRPM...

3kRPM on a 155/80R13 (71.5" Dia, 886 R/M)

3,000/866 = 3.46 Miles per minute! (208MPH, approx)

We know this isn't possible w/ the weight vs the 50lbft of TQ, so we gear it down even more, to say: 3.3:1, which gives us an output of 1818.1818 RPM, at 165lbft TQ to the wheels.

Same tire, 1818.1818 -

1818.1818/886 = 2.05 miles per minute (approx 120 MPH). With an output of 165lbft of torque, this seems quite possible!

Do I have this right? Or am I fudging my numbers somewhere? B/c honestly, that seems WAY too easy.
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