Inrunner

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The term inrunner refers to a type of brushless motor used in radio controlled models, especially in reference to their use in aircraft to differentiate them from outrunners.

Inrunners get their nickname from the fact that their rotational core is contained within the motor's can, much like a standard ferrite motor.

Compared to outrunner motors, inrunners tend to spin exceptionally fast, often as high as 4200 RPM per volt, far too fast for most aircraft propellers. However, inrunners lack torque. As a result, most inrunners are used in conjunction with a gearbox in both surface and aircraft models to reduce speed and increase torque