Wednesday, October 14, 2009

A Electric Mini RC Helicopter Inside Look

This little electric mini RC Helicopter wonders into my backyard due to pilot error. So I capture the intruding aircraft. Here is a review of the enemy technology used in the aircraft.

Interesting thing to note, the tail rotor is mounted horizontally rather than vertically. This leads me to think that this is use to control the forward/backward motion of the rc helicopter. Tilt the tail up and the helicopter will move forward, tilt it down ( by reducing the speed of the rotor ) and the helicopter move backwards. The flight pattern is somewhat like a humming bird I think when it is sucking up nectar.

There are actually two main rotors. One is use to move the helicopter up and the other is used to move the helicopter down. This is probably down to reduce the complexity of the drive electronics and also to reduce cost. There are no complicated electronics to change the direction of the rotor with just one motor. The two motors may also be needed to balance the helicopter since the drive motor is mounted off center in the helicopter chassis.

Note the use of the lithium polymer battery, for its high power to weight ratio. The battery itself does not have a metal casing further reducing the weight.

Note the comments on the battery that the battery should not be charged by children. Yet electric rc helicopters like this are frequently given as toys to children. I supposed its is really safe if you use the charger supplied. ( Lithium polymer battery may explode or catch fire if improperly charged )
This low cost rc helicopter also does not have battery protection circuit to shut off the battery when the voltage drop below the recommended 3V for a Li-Po battery. This can also results in abrupt termination of flight when the battery goes flat in mid air.
A possible improvement to this electric mini RC helicopter would be to use a single brushless DC motor to drive the main rotor. The will considerably lighten the helicopter possibly prolonging the lithium polymer battery life. Brushless DC motor are also more efficient.