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Old 05-30-2012, 02:21 AM
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Join Date: Apr 2008
Location: Wisconsin, USA
Posts: 8,952

Originally Posted by danauti1 View Post

my only question is can I swing a smaller prop than the recommended if I go for the larger motor?? the plane can onlly handle about an 11 to 12 inch prop...
You've really got to watch the prop size with these electric motor power systems. These motors are pretty much constant RPM power plants, as compared to a glow engines constant torque type power plants.

So, taking an electric motor setup designed for say, 14X8 prop, and putting a 10X8 on it will REALLY kill power output.

Take the hacker A50-12S motor as an example, running on a 6S LiPo.

Motocalc suggests this motor running with a 10X8 prop will turn over at about 10,500 RPM, pulling about 22 Amps and 500 watts, with 60 ounces of thrust.

Upgrading to a more reasonable 14X8 Prop, that motor/battery will turn over about 9600 RPM, pulling about 66 Amps and 1400 watts, with about 180 ounces of thrust. What with what appears to be a reasonable propeller size change can have a very drastic change in power output, and along with that current input to your motor.

This is why so many wattflyers indicate that it is mandatory to pick up one of those wattmeters to measure what current/voltage/watts your power system is running, so as to not burn anything up. These motors are DUMB. They will happily turn over far to big of a propeller. Until the magic smoke comes out.
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