Wednesday, 23 January 2013

Quadrotor Calculations

Sorry for the boring post, but I'm sick of having to do these out on paper over and over again and losing it. So a quick cheat sheet solves all my problems, here is a quick non flying video (first loaded test, with power issues)


Battery = 11.1 V (LiPo) 6000mAh Discharge 25C Burst 50C

Discharge rates in Amps
C Rate * Capacity (Ah) = Discharge rate in Amps

  • 25C *6000e-3 = 150Amp
  • 50C *6000e-3 = 300Amp

Motors = 950KV 3cell Outrunner Brushless Motors W/ Prop adapter Type A2217/9 200Watt (x4)

Full power current requirements
200W = Volt * Current
200W = 11.1V*Current
Current = 200W/11.1V
Current = 18Amps
  • 1 motor = 18Amps (At full power)
  • 4 motors  = 72Amps (At full power)
But full power is only used by individual motors for maneuvering
Full throttle = 50% power
  • 1 motor = 9Amps (At full throttle)
  • 4 motors = 36Amps (At full throttle)
With Props = 10x4.7

Motors rated for 950rpm/volt
Total RPM = 950*11.1 = 10545
Statics thrust = 1.40kg
Required engine power(Watt) = 275W
But our engine power is limited to 200Watt
So assume engine max RPM = 9500
Static thrust = 1.14kg
Required Engine Power (Watt) = 201W

Quad Mass = ~2.1kg
At full throttle 1 motor will produce = 0.57kg of static lift
At full throttle 4 motors will produce = 2.28kg of static lift

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