Ever thought about designing your own model? its all to easy just to fit your radio gear to the RTF you bought down the local model shop, all the thinking is done for you.
But its much more fun and involving if you take the time to design your own model, you will soon discover a side to our hobby that only a small amount of modelers experience, and you will learn about aerodynamics, what works and doesn't, and most importantly you will be able to say "I designed and built it myself".
Here are some useful sections that should help you with your design.
An introduction to electric powered flight. Their has been huge advancements in electric motors & batteries over the past few years, gone are the nicads that weighed has much as a brick and the carbon brushed motors, these have been replaced by light weight Lithium Pollimer (LiPo) batteries that are light and capable of delivering large amounts of current, and D.C. Brushless motors that use induction rather than carbon brushes.
Their are two main types of motor, the Innrunner & the Outrunner
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to our Hints & Tips Page
The Innrunner motor This works like a traditional D.C. motor but without the carbon brushes, the rotor is made up of the windings and the stator are the magnets fastened to the case. These motors are used for high speed models (high rpm) that turn small props and don't need large amounts of torque (turning force).
The Outrunner motor is widely used for turning larger props especially on electric powered gliders, because the rotor is the outer casing that also contains the permanent magnets, this produces a flywheel effect that produces a large amount of toque (turning force) compared to the Innrunner motor.
Electronic Speed Controllers (ESC) are very smart pieces of electronics, the battery provides the power to the controller (Vin) and this is reduced to 4.8V for the Battery Eliminator Circuit (BEC), the controller uses a process call Pulse Width Modulation (PWM) to control the speed of the motor by reducing or increasing the duty cycle.
The output voltage (Vout) will be about 11V when the motor is at 0 rpm, when the duty cycle is increased and the motor accelerates the voltage will drop and the current will increase.
Battery Lithium Pollimer battery's (LiPo) are capable of delivering large amounts of current for very modest weight, they are made up of cells (usually flat) that have a voltage of 3.7V, using cells also aids cooling making large discharge rates possible.
Voltage (V) , made up by the number of cells (S) so 11.1V = 11.1 / 3.7 = 3 therefore 3S
Capacity (C), in Milliamperes (mA) 2500mA = 2.5Amps
Discharge Rate, (in this case 20C) therefore 20 x 2500 = 50000mA or 50A
II hope this makes the basics of electric flight a bit clearer, if you need help in chousing your first electric setup a good model shop with knowledgeable staff is essential,
Tony Hill Models will give you all the help you need, just give them a call.
"Everything should be made as simple as possible, but not simpler." - Albert Einstein
