# Finding motors

So after doing the math for a project coming up I have calculated that I need a motor with close to 27 watts (0.0362076 hp) output power that must run on less than 9 volts input. My preference is for it to run on a 2s lipo (7.4 volts) but I'm not picky. Brushless or brushed doesn't matter either way (if brushless I would need an ESC that has breaking capabilities) Any suggestions on how I would find such a motor

The highest wattage motor DigiKey has with a rated voltage between 4.5 and 9.0 is a 13W (6V, 10000 RPM ). They have 12V motors at 33W and 35W but all the other motors in the 26 to 35W power range run on 24V. Have you thought abut finding a motor that has the power and speed to do what you want and then picking a power supply to match?

Hobbyking online

Unfortunately the rules do not allow a voltage over 9 volts.

I suspect you may need to over-power your motor to get the output you want - with a small risk of overheating the motor.

Is there a limit to the physical size of the motor?

It's a long time since I was familiar with the wattage numbers but a low voltage (i.e. 3v or 5v) 540 size motor should meet your need. For 27watts at 9v you will need about 6 amps (allowing for inefficiency) and even the smaller motors can take that for a limited time. I have some smaller motors that could take 9 amps - I think they may be a 230 or 250 size, but I can't be certain. (And I don't know what those numbers refer to).

...R

Cool thanks. These are only running for a short time so I can definitely over power it. I'm not sure what those sizing numbers mean though.

jjrreett: I'm not sure what those sizing numbers mean though.

See what Google does with them.

Read some of the electric flight magazines or Forums - those folks get all they can from the motors.

...R

Robin2: See what Google does with them.

Very little. Motor size numbers (130, 540, etc.) have never made sense to me either.

This Mabuchi web page has good info for the small motor sizes

Google "540 electric motor" finds plenty of suppliers.

...R