Today I’m looking at one of the components that can make a huge difference when it comes to building a fast drone, the motors. This article will look at what makes a motor good for a particular application and compare some of the most popular motors.
FPV racing drones rely on four brushless electric motors (hence the term quadcopter), along with speed controllers and propellers for thrust. I’m going to be giving an overview of what you need to look for depending on your flying style/track and which motors are best. I’ll be providing options for both cheap FPV racing drone motors and higher quality, more expensive options.
FPV drone motor sizing guide
Motors come in many different sizes and speeds, so understanding what all the numbers mean will help you get the right motor for the job.
The size is expressed by four numbers, the first two detailing the stator diameter and the second two relating to the stator height. For example a common 2205 motor has a 22mm diameter stator that is 5mm high. The motor torque is proportional to the size of the stator, but the larger the stator, the heavier the motor. Selecting the correct motor is therefore important, as an oversized motor just adds to the overall weight, reducing flight time and responsiveness.
The second four numbers (followed by the letters kV) refer to the speed of the motor. The higher the kV of the motor the faster it’s top speed/RPM. A typical motor designed for use with a 5″ prop may have a rating of 2000-2700kV. The RPM of your motor can be calculated by multiplying the kV with the Volts supplied by your battery. i.e. a 2300kV motor running at 16.8V (4S) would have a maximum speed of 38,640 RPM.
Higher motor speeds allow you to go faster, but also draw more current from your battery. A prop with a large amount of thrust, such as a 5050 tri-blade, will cause your battery to sag significantly if running on a 2600kV and above motor, so would be much better paired with a 2300kV or lower motor. A higher top speed also provides less control, as each percent of throttle increase corresponds to a larger change in thrust. High kV motors are typically used with smaller or lighter (lower thrust) props, such as bi-blades, to offer good efficiency and high top end speeds.
Lower kV motors twinned with larger props offer increased efficiency, whereas using a heavier (larger thrust) prop with a lower kV motor offers increased low end thrust for changing direction.
Best motors for FPV drone racing
When drone racing, the course type will heavily influence the ideal motor. For example a course with long straights and sweeping corners will be best suited to a high speed motor. As direction changes are small, heavier motors can be used to provide more top end speed.
A good motor here is the 2750kV version of the EMAX RS2306
A cheaper alternative is the Racerstar BR2306S 2700kV
For tight, twisting courses, overall weight has a larger influence and keeping the drone’s weight as low as possible is advantageous. A light weight motor with lower speed, but good torque/throttle response, will help with cornering.
Racerstar provide a cheaper alternative here too, with the Racerstar BR2205S 2300kV
Best FPV drone motors for acrobatic flight
For acrobatic flying, where speed is not a critical factor, motors with a large amount of torque and good punch are best. Being able to pull out of a dive at the last minute or punch up over a tree, requires a heavier prop and a motor that can spin it. It is becoming more popular to run larger stator diameters of 23mm (compared to the standard 22mm), as these offer good low throttle torque.
A cheaper alternative is the Racerstar BR2306S 2400kV
Cheap drone motors
It’s important to remember that when it comes to drone components, you do get what you pay for. Cheap components are unlikely to be made from the same high quality materials, or be subjected to the stricter quality controls, that you would expect from more expensive components.