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Props, amps, and speed

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Old 03-13-2006, 01:00 AM
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nuclear_cv
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Default Props, amps, and speed

Well, I'm a semi-newbie to rc planes and I have a question. What size props pull more amps and which pull less and what are the advantages of having a big diameter prop v.s. a small one?
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Old 03-13-2006, 05:52 AM
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panzerd18
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Default RE: Props, amps, and speed

Bigger props put more load on the engine thus draw more amps.

Put a too bigger prop on it and it will draw so many amps it will burn the motor out.

What you want to do is turn as bigger prop as you can but not too big to pull so many amps to burn the motor out.

Big props will create more thrust than smaller ones as a general rule, however the smaller ones will spin faster and the bigger ones slower. For an speed plane you want a smaller diameter prop with a higher pitch, for better acceleration and climb performance you want a prop with a larger diameter and lower pitch.

Another confusing thing is that motors are most efficient at a certain RPM. You don't want to put on a put that only spins at 5000rpm when its more efficient at 10,000rmp. To rectify this you would put on a smaller prop to get the extra rpm but then you loose thrust doing so.

Electrics are very interesting, i'm still learning so it could be wrong. What I did was play around with electric motor calculators.

http://brantuas.com/ezcalc/multiplexcalc.asp

http://www.csd.net/~cgadd/eflight/calcs.htm

http://adamone.rchomepage.com/calc_motor.htm

http://www.flyingmodels.org/motortest/index_e.htm
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