Milton says, "Never leave your li-poly batteries charging unattended"
The Brushless Edge
In areas where noise is a concern and for people who like to fly gliders but don't have enough space for a launching system, electric motors offer a great way to get your airplane in the air. Scale model airplanes can be powered by electric motors, as well as ducted-fan jets and multiple engine models. With one battery charge you can climb to your desired altitude several times. If you decide to have an electric motor for your glider, flights can last as long as 30 minutes.
Two Basic Types of Motors
Motors vary in size and the number of battery cells needed to power them. There are two basic types of motors, brushed and brushless.
Brushed motors use "brushes" to conduct electricity to the commutator, which then conducts the current to the armature. The commutator and armature are two parts of the same assembly, and spin in the middle because of magnetic fields generated by the batteries power. Magnets bonded to the inside of the motor case interact with these magnetic fields and that make the commutator and armature turn.
In 1992, Aveox introduced the first commercially produced brushless motor designed for modeling use. The basic operating principle of a brushless motor is essentially the same as the more common brushed variety, but the construction is quite different. In a brushless motor, the permanent magnets are located on the rotor or armature and the windings are stationary and attached to the motor's outer case. Since the windings do not rotate, the commutation must be done electronically rather than mechanically. A microprocessor circuit that includes an integrated electronic speed control performs this electronic commutation.
The Brushless Advantage
There are several advantages to upgrading from a conventional brushed motor to a brushless motor. The most obvious advantages are more power, longer runtimes and virtually limitless motor life. The heat generated in the windings is more easily dissipated, since the windings are in direct mechanical contact with the motor case (which acts as a heat sink/radiator). In addition, overall resistance is significantly reduced, resulting in a higher overall efficiency. In fact, a brushless motor can often operate at 2 or 3 times the power output of an equivalently sized brushed motor. A side bonus is that brushless motors have less electrical noise that could potentially interfere with the radio signal.
Ultimate Efficiency & Performance
A wide variety of brushless motors is now available from many companies such as AstroFlight, Eflite, Hacker, Multiplex and Kontronik as well as from several other manufacturers. Offerings from any of these are worthy of serious consideration if you want the ultimate in efficiency and performance to power your next electric model.
If you power your model with an electric motor, you will need support equipment. The basic power system is a motor, electronic speed controller, arming switch, fuse and a battery pack. Their capacity is rated in milliamp hours (mAh) and you can expect run times of 3 to 7 minutes from 6 and 7 cell packs, depending on the amp draw. Amp draw is affected by propeller size and pitch, so you should choose the right prop.
Direct Drive or Geared Drive
A motor may have a direct drive or a geared drive. If you need help choosing, all you have to know is what you are going to use it for. If you want high powered but short flights like for racing, then you would want a direct drive motor. If you want a slower but longer more casual flight, then you want a geared drive. Another factor that should be taken into consideration is the propeller size. The larger the prop, the more likely you will need a geared motor. You basically just have to match your motor's power requirements to efficient amp draws.