Which motor to use for UAV?
The primary candidate to be a motor for this aircraft is the Emax RS2306. Very reliable motor with excellent performance. Total output of the aircraft is expected to be around 3 kilowatt and thrust of around 5 kilograms. The Emax RS line is very reliable and can handle plenty of abuse.

Emax RS2306
The second candidate is the savage T-Motor F40 Pro VI. The slightly higher price will get us more power than we'll ever need, easily going over 5 kilowatt and around 7 kilograms of thrust. This transforms the 300-400 gram drone into an absolute rocket ship. The T-motor is a top of the line manufacturer of motors so reliability is unparalleled.

Tricopter Reptile Mosquito Y400Y
Part of UAV motors
Motors are generally rated by their size usually with two numbers such as 2205. First two numbers indicate wider motors in diameter, second two numbers indicate taller motors. Increasing or decreasing each number has a direct effect on its speed and torque.

Smaller motors tend to have lower torque but spin much faster to compensate for that. Smaller motors are also inefficient in relation to their larger counterpart. In example, a 2205 motor could consume 50 amperes at 16 volts to generate 1500 grams of lift, whereas a bigger 3620 motor could achieve the same lift by consuming only 15 amperes at the same voltage. Of course, the efficiency of the bigger motors comes with a cost, which is weight.

Another rating of the motors is the kV, which doesn't stand for kilovolts. Instead this is a rating which indicates how many revolutions per minute the motor spins for each given volt. In example, a 1000kV motor will spin 12.600 times per minute when powered by a 3 cell, 12.6 volt battery. Generally lower kV motors work best with bigger propellers and this setup is more efficient.

The motors used in UAV's are mostly brushless tri-phase motors requiring their own computer to help them spin. These motors are completely immune to water so they can be submerged and still work perfectly fine.
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