Maybe you’re new to the drone hobby, or maybe you’ve flown drones for years. Either way, you’ve undoubtedly seen quadcopters: small, remote-controlled helicopters shaped like an X with four propellers, one on each corner. Today we’re focusing on how to choose and install electric quadcopter motors in your drone project. You’ll want to choose your motors very carefully based on what you want your drone to do, how fast and high you want it to fly, how long you want to stay airborne, and what you’re prepared to spend.
What Are Quadcopter Motors?
Inside the Motor
Electric quadcopter motors have two main parts: the rotor and the stator. The rotor has either a permanent magnet or an electromagnet, and the stator surrounds the rotor with “poles” connected to the battery and the control system. When you apply power, each pole generates a magnetic field to pull the rotor from one pole to the next, causing the rotor to spin a propeller. Its speed depends on how much power you apply, but can range up to thousands of revolutions per minute.
Your drone has a Central Flight Controller chip that translates your desired flight pattern into instructions for its motors. The CFC sends signals to each motor’s Electronic Speed Control chip to manage how fast and which direction to spin its propellers. The ESCs take power from the drone’s battery and switch the motors’ electrical current on and off many thousands of times a minute per motor. Based on the computerized flight plan or your remote-control instructions, the CFC can command each motor to turn its propeller faster or slower, creating thrust to push the drone upward, roll, slide, change direction, or hover in place.
The Various Types of Motors
Just as a car does not have the same kind of motor as a dump truck, a large drone used for aerial photography will need different motors than a small racing drone. Unlike a car, you’ll need four of the same motors for your quadcopter to take flight. Quadcopter motors are designed for top speeds from hundreds of revolutions per minute to almost 30,000 RPM. These motors aren’t always cheap, but they are essential to making sure that your drone stays airborne and performs the work you need.
First, calculate the weight of your quadcopter, including your anticipated payload as well as the propellers and motors you want! This dictates your thrust requirements. For instance, a 400g quadcopter needs a minimum of 400g of thrust in order to hover. That said, your quadcopter won’t be able to lift off with only 400g of thrust! To climb and maneuver we recommend a power-to-weight ratio of 2:1, meaning that a 400g quadcopter actually needs 800g of thrust at full power or 400g at 50% power. Some enthusiasts install even more powerful motors for 3:1, 4:1, or even 10:1 ratios!
Brushed DC Motors
Some older or very inexpensive drones still use “brushed” direct-current motors. These are the original type of electric motor, using a rotating switch and carbon “brush” contacts to transmit electricity to the electromagnetic rotor. These motors create noise and sparks, they sap power, and the brushes may burn out quickly, often within hours. If you can, try to invest a little more in your drone to avoid this style of motor.
Brushless DC Motors
Today, the most common quadcopter motors are the brushless direct-current motor and the similar permanent-magnet alternating-current motor. Their rotors are built around a permanent magnet with no electrical connection to the motor housing. They are more efficient, more reliable, and have a higher RPM than old-style brushed motors. We recommend that you look for this technology when purchasing new motors for your drone.
Barrel-style brushless DC motors are shaped like a skinny barrel or tube and are the most widely used quadcopter motor. They have few electrical poles and spin fast, and should be paired with small, lightweight, multiblade propellers. Choose this option if you have a lightweight quadcopter, want speed and agility for racing, or are a beginner on a budget, though they often produce more vibration and noise than disc-style motors.
Quadcopters with larger propellers need motors that spin slower and create more torque (twisting power). For these drones, a disc-style brushless DC motor may be best. They are short and squat with many poles, which allows them to produce maximum power at lower RPMs and more smoothly and quietly than barrel-style motors. These qualities make them great for heavier drones, aerial photography, and expert operators, but they tend to be more expensive to purchase than barrel-style motors.
Power Rating and Supply
Each type of motor has a different power and RPM rating and needs different voltage and amperage. Just as you need more power to move a dump truck than a car, your quadcopter motors need to overcome more air resistance and weight to hoist a heavy, bulky quad than a flyweight model. If your quadcopter doesn’t need to fly quickly, maneuver much, compensate for wind gusts, or carry a heavy load, you might use lower-powered motors that use less battery power and keep you aloft longer. If you want to do aerobatics, carry heavy cameras, or stay stable in strong winds, your quadcopter motors need to be more powerful and you’ll have lower flight time. Check your drone’s manual before you buy so you get motors that match your control system’s power ratings.
How to Install a Quadcopter Motor
Before installing new quadcopter motors, it’s useful to have some tools and materials on hand. Check your motors to see if you need any special tools, but here is a short list to get you started:
- Small needle-nose pliers
- Screwdrivers, both miniature and regular-size
- Anti-static pad
- Bright work lamp
- Soldering iron and solder
- A multimeter, to check the motors and chips for problems before you install them
- The instruction manual for the motors
- The manuals for the drone’s Central Flight Controller and Electronic Speed Control chips
Important: Be Safe Around Batteries
The first step when working on your drone’s electrical system is to always disconnect and remove the drone’s battery, and then ground out any remaining charge in the drone’s capacitors. Lithium-ion batteries catch fire or explode if you short them out, damage them, or puncture them! If you remove the battery, it also means you won’t cause damage to the drone’s electronics if you do accidentally have a short circuit.
Attaching the Motors
Pick quadcopter motors that are designed to fit your drone without much trimming or drilling whenever possible, so you don’t have issues with balance, vibration, or frame strength. Attach the motors using the manufacturer’s recommended hardware or adhesives, which may include soldering wire connections. Be very careful to attach the positive (+) wire to the motor’s positive terminal and the negative (-) wire to the negative terminal!
Consider whether your quadcopter motors need new propellers. The propeller’s thrust level depends on their size, air resistance, angle or pitch, blade count, and speed. If you replace high-RPM barrel motors with low-RPM disc motors, you should consider larger propellers with a lower pitch instead of small multiblade propellers. Raising the power level might also mean switching from cheap plastic blades to high-quality carbon fiber blades.
Keep It Centered
After installing new quadcopter motors, you should check your drone’s center of gravity to make sure it won’t tip to one side when flying. You may also need to reprogram your drone’s control software to ensure that the Central Flight Controller, Electronic Speed Control, any Battery Management Control chip, and the Remote Control Station recognize the new motors and propellers. New electrical components will draw different levels of power, which may even mean installing a new, larger battery.
Newton stated that each action has an equal and opposite reaction, which means that when a motor shaft turns in one direction, the motor housing tries to twist the opposite way. Unless you want your entire drone to spin in a circle like a disco ball, make sure two motors rotate one direction and two rotate the other way! This is the most common pattern for motor installation:
- Front left: clockwise
- Front right: counter-clockwise
- Back left: counter-clockwise
- Back right: clockwise
Finally, be sure that you install your clockwise propellers on the clockwise motors and vice versa.
The motors are the heart of your quadcopter. Whether you’re building a large, advanced quadcopter or a lightweight barebones craft, you’ll need a matching set of four quadcopter motors that balances power, responsiveness, weight, and affordability. Check out our reviews to find the best models to suit your drone and let us know in the comments what you think!