what brushless motor to use

by Tom
(Lake forest CA)

I have a P51 mustang that came with a glow engine.I want to convert to a brushless electric motor, how do I calculate what motor to use?

Is it by plane weight wing surface area, or a combination of several factors.

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what brushless motor to use

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Watts/Pound Ratio
by: Tom Bennett

I found a chart on the centralhobbies.com/electricflight website. It shows different types of models and suggests a wattage per pound of weight for each type.

choosing a brushless motor
by: Matt

Hi Tom,

I'd being lying to you if I said I knew exactly how to pick the perfect motor for any given airplane.

There is really no straight forward way to choose a motor. It depends on many factors.

First you have to choose between an outrunner motor and an inrunner motor.

An outrunner motor produces more torque and spins slower than an inrunner. So you would use a larger prop that spins slower. Outrunners are also very quite, which I really like.

Inrunner spin really fast, so they need a gearbox to reduce the speed. Inrunners generally provide less torque with more speed. So now you have to not only pick the right size motor, you also have to decide on what size gearbox to use.

The motor you choose also depends on what type of aircraft you have, and your particular flying style.

When sizing a brushless RC motor, you also have to decide what is more important to you, speed or thrust. It's almost like choosing a propeller. You have to sacrifice speed for thrust, and vise versa.

I find it easier to use what the airplane manufacturer recommends or do some research to see what has worked well with others.

Electrifly's Website has an awesome free program that will assist you with choosing the right size brushless motor for just about any size or type of RC airplane.

Of course they are going to recommend an Electrifly Motor. But you can then look at the specs of the recommended motor and compare with other brands of brushless RC motors.

I hope this helps. Please let me know if you have any more questions.

Let us know what you pick and how it works out will ya?

Thanks,

Matt

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Submitted by: Matt

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Hi Tom, I'd being lying to you if I said I knew exactly how to pick the perfect motor for any given airplane. There is really no straight forward way to choose a motor. It depends on many factors. First you have to <a href="http://www.hooked-on-rc-airplanes.com/brushless-rc-motors.html#4"> choose between an outrunner motor and an inrunner motor</a>. An outrunner motor produces more torque and spins slower than an inrunner. So you would use a larger prop that spins slower. Outrunners are also very quite, which I really like. Inrunner spin really fast, so they need a gearbox to reduce the speed. Inrunners generally provide less torque with more speed. So now you have to not only pick the right size motor, you also have to decide on what size gearbox to use. The motor you choose also depends on what type of aircraft you have, and your particular flying style. When sizing a brushless RC motor, you also have to decide what is more important to you, speed or thrust. It's almost like choosing a propeller. You have to sacrifice speed for thrust, and vise versa. I find it easier to use what the airplane manufacturer recommends or do some research to see what has worked well with others. <a href="http://www.electrifly.com/powersystem/powersystem-index.html" target="_blank">Electrifly's Website</a> has an awesome free program that will assist you with choosing the right size brushless motor for just about any size or type of RC airplane. Of course they are going to recommend an Electrifly Motor. But you can then look at the specs of the recommended motor and compare with <a href="http://www.hooked-on-rc-airplanes.com/brushless-rc-motors.html#VisitorPages">other brands of brushless RC motors.</a> I hope this helps. Please let me know if you have any more questions. Let us know what you pick and how it works out will ya? Thanks, Matt

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Reply
by: Anonymous

Matt,
This is a 1/12 scale P51 mustang. it had a .061 size motor. Its not just replacing the motor by asking, I'm really into learning more about how to calculate motor sizes for different planes. any information you can give me would be greatly appreciated,
Thank You
Tom

What is your current engine?
by: Matt

Hi Tom,

What size plane and what engine do you currently have?

When converting from glow to electric it's easier to find a motor that matches the output of the current engine.

Matt