Inrunner motor & Outrunner motor

There are two types of brushless RC motors for RC Helicopter, Inrunner motor and Outrunner motor .The permanent magnets of inrunner brushless motors are positioned on the inside of the electromagnets.

Inrunner brushless motors are set up very similar to the canned motor explained above, except the permanent magnets and electromagnets are in opposite positions.

An outrunner brushless motor has the permanent magnets on the outside of the electromagnets. You can see in the picture to the right that the outer hub holding the permanent magnets has the output shaft attached in the center.

Inrunner Brushless Model Aircraft Motors
The faster a motor spins, the more efficient it is. Inrunner motors turn very fast and are much more efficient than outrunner motors. Inrunner brushless RC motors require a reducing gearbox between the motor and propeller of your RC airplane. For this reason, the output speed and torque of the propeller can easily be "tweaked" to facilitate different flying characteristics by using different size gears.

The downside is added parts that can and do fail. The gears get stripped, and the gearbox shafts are easily bent. It can also be an obstacle when mounting the gearbox motor combination for your RC airplane neatly, especially under a cowling.

Inrunner vs Outrunner

Outrunners motor
# Low RPM's, high torque
# Less efficient than inrunners
# No gearbox required
# Narrow prop selection
# Silent

Inrunners motor

# High RPM's, low torque
# More efficient than outrunners
# Require a gearbox
# Wide prop selection
# Noisy

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