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Trade Study 2

Motor Selection and propeller matching

Hadrien guepet

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Conclusion from the previous trade study

We will use a propeller with a 0,7 tau ratio

The Bigger the Diameter the better the efficiency is.

A electric motor need a small propeller to avoid avoerloading your electric motor at static thrust

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Propulsion System

Battery controller Electric Motor propeller

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brushless electric motor modelling

ElectricPower (Bat)

Power Diagram

Controller Loss

Mechanical power

Copper loss due to wiring

Iron loss due to hysteresis and eddy current

friction

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Comparaison between our model and experimental results

KV 1100

Tension 3S:11,1V

I0 2A

Rext 0,025 ohm

Rmotor 0,025 ohm

After comparing 10 motors : 4% error max

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Our Propeller : 12 x 8 APCE Performance Chart :

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Power required and prop efficiency for our aircraft

Design point : 25° at 40ft/sPower required for the propeller : 342W @ 8210 rpm

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Motor matching

According to our model a motor with a KV of 977 will match perferctly exactly

The closest possible choice is a 1000KV motor

We choose The Turnigy SK 3548 1050KV

(the smaller SK 3542 could fit but we want to be sure it

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Selected motor Turnigy Aerodrive SK 3548 --- 1050 KV

KV 1050Tension 3S:11,1V

I0 2A

Rext 0,025 ohm

Rmotor 0,025 ohm

Weight 0,391lbs

I max 50

Power 0,75hp

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Efficiency diagrams

Climb cruise

https://www.youtube.com/watch?v=GrrJoOSR4W8

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Aircraft performance

Max speed about 83 ft/s

Max climb speed = 40 ft/s

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Speed diagram

Stall Speed

20 ft/s 22,5 ft/s

Speed for max angle of climb

(33°)

40 ft/s

Choosen cruise speed

45 ft/s

Max speed at 25° of climb

49 ft/s

Speed for max Vz (19ft/s max)

83 ft/s

Max speed in level flight