There are certain considerations and rules which you must remember while selecting effective quadcopter motors .
Decide the Quacopter Motor Size
The first thing you need think about is the motor size which you will need for your quadcopter. You need to ask yourself two questions for this purpose:
- What is the size of your quadcopter’s frame?
- What is the planned total weight of your quadcopter?
When talking about the size of the frame, you must be aware of the maximum propeller size that can be used in your model. When talking about the planned total weight, you must take everything into consideration including battery, frame, motors, wires, ESCs etc. By knowing the answer to these two questions, you can get a rough estimate of the size of motors you will actually be needing.
Thrust To Weight Ratio
The rule of the thumb is that at least twice the amount of weight should be available as thrust. If the thrust provided by the motors is not sufficient, your quadcopter would not respond well to the control. It may even face difficulty while taking off. For FPV drones, the ratio between thrust and weight should be higher. Maybe 8:1 or 10:1. But if this ratio is too high, the quadcopter would become very hard to control.
Quadcopter Motor Size And KV
The wider and taller the motor, the more torque it can generate.
KV is another important parameter which will influence your choice of motor. Theoretically, it means an increase in the motor’s rotations per minute when the voltage increases by 1 volt without load. Motors with higher KV would try to spin the propeller faster. Lower KV means usually generate a higher torque. It is for this reason that we tend to see larger props are matched with low KV motors whereas smaller props are attached with high HV motors.
N And P
In case you see something like ‘12N14P’, you must not get confused. The numbers before letter ‘N’ (in this case ‘12’) denotes the number of electromagnets in the stator and the number ‘14’ denotes the permanent number of magnets in the motor.
In case you find that a particular motor has more electromagnets and permanent magnets, it simply denotes that the torque produced by that particular motor increases more efficiently.
Your motor will spin harder when a high voltage is applied and thus it will draw higher current. Thus it is always important to understand the voltage and current drawn by a motor before choosing it.
Comparing Quadcopter Motors
Thus, in short, following factors need to be considered for selecting the best motor for your quadcopter:
- Current Draw
Other important factors which may influence your choice are:
- Best props
Some other features of motors which might grab your attention are:
- Type of magnets
- Solid/Hollow shafts
- Cooling design
- ESC integration
- Arc magnets
- Smaller air gaps