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Old May 16, 2002, 08:04 AM
Ninjak2k is offline
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United States, VA, Warrenton
Joined Apr 2001
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How does prop RPM affect power?

I just got AstroFlight's Electric Motor Handbook and I'm trying to puzzle out something regarding the power you get from a motor.

As a for instance, on 10 V you could prop a motor to draw a certain current, say 20 amps. Now, you can then use a gear box to swing a bigger prop at the same 20 amps, but get more thrust. The system you have is still generating 200 Watts, right? But now your RPMs are reducing. Theoretically, you could continue to increase the gear ratio and keep propping for 20 amps and your system is still a 200 W system, right? But your RPMs will go down, down, down...

What is the effect of RPMs on performance? Your system may be using 10 volts and 20 amps, but as you increase the gear ratio, are you really getting that 200 W in the air? What RPM range should you shoot for for good flight?

Dan Nash
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