|Electric Flying - Basic Concepts|
Electric flying is something I've just got into myself! I have been flying over 21 years but wanted to try this side of the hobby. I do not profess to know the ins and out and all the technical details of watts, amps, milliamps, brushless motors or the number of turns required to make a hot motor. But outlined below are some of the basic things I have learnt while getting into the electric side of our hobby. I hope it will help you understand some of the basic concepts.
Indoors Or Out?
All these models are made of expanded polystyrene foam. This gives them a very light structure and cuts down on building time. The standard electric motor is the Speed 400 or Speed 480. These are usually used without gearboxes (direct drive) in the above examples. They use plastic 'Gunther' props (usually supplied) which just push on to the motor shaft or a props around the 6x4 size, which will require a small prop adapter.
Most ESC's have what is called a Battery Eliminating Circuit (BEC) this means that all your on board radio gear (rx, servos) are powered from just the one motor power pack, thus eliminating the need for a separate battery to power your radio gear. When the power pack discharges to a fixed voltage during flight, the BEC will automatically cut the power to the motor(s) at that point, but continue to supply the receiver. This allows you to land safely with out loss of radio communications.
ESC's are rated at different ampreages, from around 2 amps to 50 amps. You choose the one to suit your power pack and motors. In the above examples the Twin Star usually uses a 7 or 8 cell pack (8.4v - 9.6v), which will draw around 20 to 30 amps. In this case an ESC rated at 35 amps would suffice.
Power Packs & Charging
Conversely, a 2000 mAh pack can be charged in 1 hour if supplied with 2 amps! There are many fast chargers on the market. All have their pros and cons. I use the Super Nova 250s. At around £70 it has features that more expensive charger don't have. It will charge and discharge your power packs automatically, both NiCad and Nickel Metal Hydride (NimH). But you can also set in your own rates manually as well if you wish. (See the diagram in our 'How To' section). It can also charge your 12v field battery (Pb - plasma battery). One disadvantage of the Super Nova is that it runs from a 12v supply. Great at the flying field where you just plug onto your car battery, but not so good at home if you want plug into the mains! However, transformers are available. (You will need between 9 and 15 v constant supply at 5 amps for the Super Nova. Maplins produce such a transformer for around £45). In my experience the Super Nova will charge a 2000mAh pack in around half an hour.
One final point about batteries. A new pack must always be given a slow charge for the packs first charge. This conditions the pack for fast charging by giving the pack its full capacity. If you were to give it a fast charge to start, the pack may never again reach its full capacity, thus giving you less running time. A slow charge is usually at a 1/10th (or C/10) of the pack's capacity. 200mAh for 10 hours in our example. Although in reality this is usually about 12 -14 hours.