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Electric flying

I tried to fly an electric model a few years back. It was an RCME Hushabye design (RM165). It didn't fly but it wasn't the fault of the design. The motor, RC and cells that I was using were just too heavy and the throttle was a simple on-off microswitch triggered by a servo. At the time I gave up.

When I visited a club field a little while ago I was surprised to see an electric model flying at speed and doing aerobatics. I decided to look into it.

I was astonished at the improvements in motors, batteries and controllers.

The compactness, rotational speed and power of brushless motors is impressive. It took me a while to realise that they were small three-phase star motors. I was puzzled where the driving waves came from so looked into electronic speed controllers. Not only do these produce the three phases at very large currents but they can be programmed for braking the motor, throttle response and other things. You can even change the sounds they make. The only thing I haven't yet fully grasped is how they sense the rotor position. I believe it's done using hall effect sensors.

Lithium-polymer cells are also impressive. Unless you are planning to boil a kettle, shorting them is a bad idea as I discovered. Luckily a window was nearby. That, and avoiding a full discharge, are the only vices. Otherwise they pack a huge amount of energy into a compact and light package. Graphene is now being used in Lipo batteries so I bought some. They seem to run cooler, probably due to lower internal rsistance. It is said that they can be recharged many more times than conventional ones. I don't yet know, but several standard lipos have started to swell and lose peak power but, in identical models, none of the graphenes have. Worth the extra I think.

For a picture guide to power connectors click here

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(C) Peter Scott 2015

Last edit 25 October 2016