Electric Model Motors - Key to Indoor RC Flight
RC modelers enjoy a wide choice of quality electric motors
Indoor radio control model airplane flight is a relatively recent development of the hobby. Since the start of practical RC model aviation in the early 1960s, the heavy weight of the early radio control sets mandated the power provided by glow fuel engines.
Geared brushless electric motor on Demoiselle
There were a few tentative steps taken with electric powered aircraft in these beginning days. Early models used NiCad batteries for electrical power. The weight of these batteries made it challenging to obtain any level of performance once airborne. All of the electric motors used for these first flyers employed brushed commutator technology. Brushes were nothing more than an inexpensive way to get electrical current to the motor’s armature. These “can electric motors” were affordable and widely used in consumer products. Common can electric motors were in no way optimized for RC model flight.
Brushless electric motor and mount
Brushed motors
Brushed electric motors did not provide much power and modelers were forced to employ gear boxes to provide useful thrust. The idea behind gearing is that a large prop moving slowly through the air provides more thrust as compared to a smaller propeller operating at higher revolutions. The smaller prop “slips” past some of the airflow at these higher RPMs and is less efficient than a large, slow moving propeller.
As the idea and popularity of electric RC flight started taking root, electric model motor development accelerated as well. The most significant technical achievement with electric motors was the development of practical brushless motor technology.
Brushed motors have a metal to metal contact between the two brushes and the rotating commutator to provide the necessary electric power interruption for motor operation. Brushless motors dispensed with the brushes. There is no physical contact between the rotating and fixed sections of a brushless electric motor.
Common brushed electric "can" motor
Brushless motors
Brushless motors require specialized electronic speed controls to manage the distribution of power. ESC for brushless motors are mature designs and work exceptionally well. Note that an ESC for a brushed electric motor will not work with a brushless engine.
Three wires characterize a brushless motor
Brushless electric model motors are the standard for RC models today. Brushless motors are affordable, come in a wide variety of sizes, and can be adapted to power virtually any radio control model aircraft.
The variety of electric motors can be bewildering to the new RC pilot. Fuel powered internal combustion engines use internal displacement in cubic inches as a useful method to gauge power between various manufacturers. There is no comparable common classification system for electric motors.
When selecting an electric motor for an RC plane, the best approach is to study the manufacturer’s technical information. All motors will come with recommendations for a certain weight and size of RC model airplane. This will be your best clue for choosing the proper engine. If in doubt, select a motor a bit more powerful than needed, and fly at a lower throttle setting.
Tiny brushed geared electric motor on the MicroScout
Brushed motors make a comeback
Interestingly enough, brushed electric motors are making a comeback with the new class of micro ready to fly indoor RC airplanes. Aircraft such as the ParkZone Cessna 210, Ember and all use tiny brushed electric motors precisely geared and E-Flite micro 4-Site propped for the model they are installed on. These carefully designed micro foam models are evenhandedly balanced between their low flight weight and the capabilities of these minute power plants. There would be little advantage trying to develop a more expensive micro brushless motor for this type of ready to fly model.
Inside view of a brushless electric motor
Another key advantage of electric model motors is ease of use. RC pilots flying with fuel powered motors are all too well familiar with a balky engine, one that refuses to start. Contributing factors can include bad fuel, poor tank location, punctured fuel lines or a failed part within the motor. Electric flight cures all these adverse factors instantly. There is nothing more pleasing than flipping a switch and witnessing instant power for your RC model plane.
It is surprising how quickly RC modelers have embraced electric powered models. Electric motors are silent and require essentially no maintenance. Electric engines come ready to run right out of the box, and do not need any sort of break in period. Electric motors last a long time. I have not had a motor failure since I started electric flight back in 2000.
Electric model motors will continue grow in acceptance with RC modelers everywhere. The inherent advantages of electric flight are quickly understood and appreciated by modelers. Electric power is affordable, easy to use and reliable - great features for any equipment used by RC pilots today.