The motors on your multicopter are the powerhouse of your build. These important pieces of hardware are where the end result of your radio inputs and flight controller calculations end up. Lets dive into the details of these important pieces of hardware. Understanding the basics will help you pick the right motor for your next build.
This article is part of a series that covers the entire concept of quadcopter parts, how they work, and how they come together. For further reading, see the master article: Components & Anatomy of an FPV Quadcopter
Today FPV miniquads are all going to be running brushless motors. These DC motors use small electromagnetic coils connected together in pairs to make up the stator. The rotor contains a set of static magnets mounted around the outside of the casing. These small electromagnets are switched on and off at very specific times by your electronic speed controller. This results in very high RPM rotation.
There are two major types of motors on the market: inrunner and outrunner. Multirotors use outrunner motors which have the rotation portion to the outside. These motors provide less RPM's but more torque than inrunner motors. This difference makes outrunner's better suited to spinning propellers.
When shopping for motors you will commonly see labeling similar to the reference chart above. Understanding these numbers can help you pick the right motors. Most often you will see the first two sections represented in most motor descriptions. The first number (2205 above) describes the motor size. The second (2300kv above) describes the speed at which the motor can turn.
The final number (12N14P above) describes the number of magnets in the stator/rotor. This number can be nice to know, but won't be an essential piece of information to consider when shopping.
Kv refers to the rotations per minute per volt or RPM/V. This number represents the theoretical number of times per minute the motor will spin with 1 volt applied. In reality the RPM will change based on many external factors such as the type of prop used. This rating system does serve as a reference point when considering the purchase of motors.
Obviously faster is better, right? Well not exactly. Higher Kv does have a higher potential RPM, but may put out less torque. A balance between RPM and torque needs to be maintained. The following general guidelines will help you decide the right motor:
Since the RPM is directly tied to volts, it is also important to consider the battery you will be using. For example a 2s battery on a 2000Kv motor will be similar to a 4s battery on a 1000Kv motor.
As we covered in the chart above, the size of a motor is represented by a number like 2205. The first two numbers (22) represent the diameter of the stator and the second two (05) represent the height. The bigger the numbers, the larger the motor, and the more potential power from larger magnets.
These days, popular sizes for brushless miniquad motors are in the 2204 - 2206 range. This size and ratio is the sweet spot for performance and there is a wide range of options in this range.
On the base of your motor you will find 4 threaded holes to mount your motor to your frame. It is important to cross reference your frame to motor mounting pattern to make sure they are compatible. The standard for miniquads is a 16 x 19mm pattern supporting 3mm threads.
Pro tip: be sure to carefully check how much thread can enter the bottom of your specific motor base when mounting. Generally 2-3mm of thread into the bottom of the motor is recommended. Measure the thickness of your frame arms and add the recommended thread depth to get the appropriate mounting hardware length. If your mounting hardware sticks through the motor base and into the stator it can cause the motor to jitter instead of spin and potentially ruin your motor.
What is the difference between CCW vs CW motors?
You will often see motors labeled as clockwise (CW) and counter clockwise (CCW). This does not indicate the direction the motor spins. Brushless motors can spin either direction. This label differentiates the direction that the motor bolt is threaded. This is done so that as the motor spins, the torque from the propeller encourages the motor nut to tighten rather than loosen. This keeps your props from loosening and coming off while you fly. This means you will need two of each for your 4 motor layout.
Pro Tip: It is quick and easy to tell if you have the correct thread for the motor direction. Just hold the nut and rotate the motor in the direction it will turn on your build. If the nut tightens, you're good to go!
Which direction do the motors on a quadcopter spin?
Common across all quadcopters, looking from the top down with the quad facing forward:
How do I change the direction a motor spins?
A standard hookup of 3 wires straight from your motor to your ESC will rotate the motors one direction. Crossing two wires or soldering a jumper on your ESC are both common ways to reverse motor direction.
Which direction do props go on?
Propellers should go on so the leading edge (higher edge if held flat) is cutting into the wind as the motor turns. Commonly propellers that are meant to be spun clockwise have an "R" or "P" marked on them. Propellers meant to spin counter-clockwise do not have this marking.
What is the motor order for my software?
Motor order is commonly used by software configuration programs like Cleanflight, Betaflight, Raceflight, or the KISS GUI. This allows you to individually control and test each motor when setting up and configuring your quad. Each program has a specific motor order that you should follow when building.
Here at Controller Craft we catalog every drone product from around the industry. Visit the motor section to find the right set for your next build.
Last updated on February 6, 2017