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# Could I rig my motor to run a bike? Answered

Okay, so I have a permanent magnet motor I was using as the generator for a Giromill (wind turbine). It's rated at 375 RPM for 120V I believe, and I'm uncertain as to its other characteristics... I've read that voltage is generally proportional to speed in a motor, and amperage to torque, so would hooking up a couple of car batteries or something similar be an effective way to power me and a bicycle around, or am I missing something (other than a control mechanism, of course)? In short, I know that car batteries can work to power a bike, but the unknown here is my motor, and whether it'd be able to work in this circumstance.

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## Discussions

Is this 120 V AC or DC... because a true AC motor will not run on DC power, it needs the phase difference in the voltage to start.... Also, 2-4 car batteries is still a crap ton of extra weight. Your motor would have to work hard enough to move the bike, you, and basically a smaller second person.

Another note, 375 RPM for a 26 " bike would be:

375 rev/min * 26*pi inches/rev * 60 min/hr * 1 foot/12 inches *1 mile/2850 feet = 53.74 MPH

So no, I don't think you would need that kind of RPM... And as you said, reducing the voltage should reduce the motor speed (that is how pulse width modulation works to control robot or other toys speeds) But reducing the voltage to the motor will also greatly reduce it's torque, even with a lot of current going to it. The only way to know if it will would still have the torque is to find a data sheet which should have that kind of information or two to build a test rig and find out.

120V? You'd be carrying a lot of lead around? The device doesn't sound appropriate for the job, from the information you've given. L

I'm assuming I wouldn't need the full 375 rpm the motor would give (would I?), and therefore could give it less voltage (like 24-48, so I'd only be hauling around 2-4 batteries). Thing is I'm not sure whether the relationship between volts and RPM is linear, or elsewise (or whether I could get a reasonable amount of torque). Thanks :)

It's the amount of power you can get into/out of this that is going to make the difference. I suppose the thing to do would be to see how it runs @ 24V. Running as a motor I'm not sure about v to RPM. L