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brushless motor selection question

I'm curious to know how to select, with confidence, an appropriate brushless motor for my scratch builds. How is this done? I believe that I understand what the "kv" rating means. Higher "kv" means more speed, less torque/power. Lower "kv" means more torque/power but less speed. However there are so many different sizes of motors, how to select one for my scratch builds?

Any help will be appreciated.

Thanks in advance!!!


I can't adequately explain the "how," but when in doubt I consult Jeff at www.HeadsUpRC.com. I prefer to order from them because their service is top notch and they have a flat rate shipping fee of $2 for all but large items (those are $4). If you give them the weight of your plane, wingspan and desired performance, they will recommend a motor/esc/prop combo for you.

To learn the "ins and outs" of power system selection, this is a great resource: http://www.wattflyer.com/forums/showthread.php?t=18521


Old age member
You must know the size of you plane.
Best is to compare with another similar plane and get what is recommended.

There are lots of recommendations of how many watts/wieght depending on the style of flying from oldtimer-scale-slow to the extreme 3D or racing planes.

KV is only interesting to compare when comparing motors in the same power range and same battery.

a big 200 KV motor will give you a lot more speed om a big plane with 12 cell LiPo battery than a 2000 KV motor vill give you on an indoor plane with 2 cells.