Worked examples determining the motor/controller requirements of your model.
1. Power can be measured in watts. For example: 1 horsepower = 746 watts
2. You determine watts by multiplying ‘volts’ times ‘amps’. Example: 10 volts x 10 amps = 100 watts
Volts x Amps = Watts
3. You can determine the power requirements of a model based on the ‘Input Watts Per Kg’ guidelines found below, using the flying weight of the model (with battery):
110-155 watts per kg; Minimum level of power for decent performance, good for lightly loaded slow flyer and park flyer models
155-200 watts per kg; Trainer and slow flying scale models
200-240 watts per kg; Sport aerobatic and fast flying scale models
240-290 watts per kg; Advanced aerobatic and high-speed models
290-330 watts per kg; Lightly loaded 3D models and ducted fans
330-440+ watts per kg; Unlimited performance 3D and aerobatic models
NOTE: These guidelines were developed based upon the typical parameters of our E-flite motors. These guidelines may vary depending on other motors and factors such as efficiency and prop size.
4. Determine the Input Watts Per kg required to achieve the desired level of performance:
Model: E-flite Brio 10 ARF
Estimated Flying Weight w/Battery: 950 grams
Desired Level of Performance: 330-440+ watts per kg; Unlimited performance 3D and aerobatics
0.95kg x 330 watts per kg = 315 Input Watts of total power
(minimum) required to achieve the desired performance
5. Determine a suitable motor based on the model’s power requirements.
The tips below can help you determine the power capabilities of a particular
motor and if it can provide the power your model requires for the desired level
of performance:
Most manufacturers will rate their motors for a range of cell counts, continuous current and maximum burst current.
In most cases, the input power a motor is capable of handling can be determined by:
Average Voltage (depending on cell count) x Continuous Current =
Continuous Input Watts
Average Voltage (depending on cell count) x Max Burst Current = Burst Input
Watts
HINT: The typical average voltage under load of a Ni-Cd/Ni-MH cell is 1.0
volt. The typical average voltage under load of a Li-Po cell is 3.3 volts. This
means the typical average voltage under load of a 10 cell Ni-MH pack is
approximately 10 volts and a 3 cell Li-Po pack is approximately 9.9 volts. Due
to variations in the performance of a given battery, the average voltage under
load may be higher or lower. These however are good starting points for initial
calculations.
Model: E-flite Brio 10 ARF
3 Cells, Continuous Power Capability: 9.9 Volts (3 x 3.3)
x 30 Amps = 297 Watts |
Per this example, the Power 10 motor (when using a 3S Li-Po pack) can handle up to 376 watts of input power, readily capable of powering the Brio 10 ARF with the desired level of performance (requiring 315 watts minimum). You must however be sure that the battery chosen for power can adequately supply the current requirements of the system for the required performance.
Examples of Airplane Setups
NOTE: All data measured at full throttle. Actual performance may vary depending on battery and flight conditions.
E-flite Brio 10 ARF
Option 1:
Motor: Power 10
ESC: E-flite 40A Brushless (V2) (EFLA312B)
Prop: APC 12x6E (APC12060E)
Battery: FlightPower Evolution20 2100mAh
Flying Weight w/Battery: 950grams
Amps | Volts | Watts Input | Watts/Kg | RPM |
37.2 | 9.6 | 357 | 375 | 7800 |
Expect good speed and extreme vertical power for artistic aerobatics. Average duration is approximately 6-9 minutes depending on throttle management.
Option 2:
Motor: Power 10
ESC: E-flite 40A Brushless (V2) (EFLA312B)
Prop: APC 11x5.5E (APC11055E)
Battery: FlightPower Evolution20 2100mAh
Flying Weight w/Battery: 950grams
Amps | Volts | Watts Input | Watts/Kg | RPM |
33.0 | 9.8 | 323 | 340 | 8700 |
Expect high speeds and strong vertical performance ideal for F3A
precision and artistic aerobatics. Average duration is approximately 7-10
minutes depending on throttle management.