Estimated reading time: 11 minutes
Undeniably, drones are currently the most popular gadget. Flying a drone is fun whether you want to capture a video or buzz around in the open field.
Nonetheless, a drone comprises a whole system of components that work together. Among them, there’s one that stands out – the propellers.
Though they function like wings, it’s tricky to understand how drone propellers work. Here’s a glimpse;
Drone propellers use force from the motor to spin. Depending on your drone’s size, the average speed of propellers spin is between 8000rpm to 9000rpm. Also, it’s essential to understand that propellers spin in different directions to counteract the torque.
If you’re a beginner or want to learn more, I’ll be answering more questions about drone propellers below.
Table of contents
- How Drone Propellers Work?
- What Are Propellers Made Of?
- What Direction Do Propellers Spin?
- Why Do Propellers Spin In Different Directions?
- How Fast Do Propellers Spin?
- How Many Propellers Are Ideal for a Drone?
How Drone Propellers Work?
Drone propellers work by using the force from the motor to spin. When the air pressure under the propellers is high, the drone starts going up. Aside from lifting the drone, the spinning also pushes forward and stabilizes the drone.
Let’s go deeper.
Generally, propellers work with thrust and lift forces. These crucial components of the drone are responsible for maintaining the drone’s balance. Besides, the propellers arrangement mainly helps to sustain the drone’s aerodynamics.
Moreover, propellers come in different sizes, shapes, materials, and even colors, depending on your drone type. Most importantly, the manufacturers have to determine the correct number of propellers and blades for different drones.
Additionally, they consider features like weight, battery life, and the drone’s size to ensure utmost performance.
Usually, propellers come with 2 to 4 blades, all for balance. More blades mean a higher lift force for spinning. But, more blades reduce the drone’s landing force.
Lastly, depending on the angle, blades enable thrust. This way, your drone can well handle the drag pressure.
What Are Propellers Made Of?
Propellers come in different types of materials, depending on the manufacturer. However, most propellers come in high-quality but soft plastic, like nylon. Still, if you want a specific material for your propellers, you could have them custom-made.
Some of the materials for making propellers are;
- Carbon fiber
- Glass fiber
- Military-grade carbon fiber
- Nylon Carbon composite
- Polycarbonate (PC)
But why is the propeller material important?
Typically, the materials play an essential role in the rigidity of the propellers. Subsequently, materials directly affect the performance of the propellers. For instance;
Plastic propellers are highly flexible. Therefore, in case of a crash, the blades remain intact and undamaged. However, they’re noisy and not an excellent choice for maintaining balance and efficiency.
Conversely, carbon fiber propellers are the ideal choice for your drone. Here’s why. They operate silently and enhance flight performance. On the downside, they need replacing in case of a crash because they damage easily.
What Direction Do Propellers Spin?
Drone propellers spin in the direction of the drone’s body, irrespective of its number of blades.
The front and rear blades move both clockwise and anticlockwise for a quadcopter. The point is to ensure they rotate in opposite directions.
Generally, quadcopters, hexacopters, and octocopters all come with sets of propellers. But things are different for tricopters! How so?
The two front propellers spin in opposite directions, whereas the rear one rotates anticlockwise.
Let’s look at the physics behind the spinning of propellers in different directions.
Drones use propellers for control and propulsion. Because forces work in pairs, the spinning propellers push down the air, and the air pushes the blades up.
Thus, there’s a lift that controls the up and downforce. In other words, when the propellers spin more, they cause great lift.
Now, here’s the thing. In a vertical plane, a drone climbs, hovers, or descends. In hovering, an equal gravitation force must pull down the drone while the four propellers push it up.
What about climbing or simply moving up? Easy! Increase the speed of the four propellers to ensure the upward force is greater than the drone’s weight.
Still, you can reduce the speed to descend. However, this case has three forces: thrust, air drag, and weight, so you also need a greater thrust than a hover.
Let’s assume that your hovering drone is facing north, but you want to rotate and have it facing east. How do you make this possible by changing the force of the four blades? I’ll need your full attention here, please.
The four rotors moving in opposite directions create zero angular momentum or torque. The angular momentum forms depending on the speed of the blades’ spin. So, there’s constant total angular momentum without torque on the drone.
But wait! Let’s number the rotors 1, 2, 3, and 4 to create a visualization for a more straightforward explanation. Decreasing the spin, blade 1 causes the drone’s rotation and reduces the speed of rotor 1.
The upward force doesn’t balance with the gravitational force, and it descends the drone. Even worse, there’s an imbalance in the thrust forces, making the drone face downward towards rotor 1. Worry not. It’s fixable!
If you want to rotate the drone without causing any hitches, reduce the spin of blades 1 and 3 and add the spin for blades 2 and 4. Still, the angular momentum of the propellers isn’t zero, making the drone rotate.
However, the total force and the gravitational force are equal, causing the drone to hover. Because the lower thrust blades are diagonally opposite, the drone remains balanced.
Forwards and Sideways-
Is there a difference between forwarding and backward motion? Not really, because the drone is proportioned. The same applies to sideways motion.
Ultimately, a quadcopter drone has all sides as the front. Therefore, moving forward is the same as moving back and sideways.
If you want to fly forward, you need the propellers to thrust forward. So, how do you get the drone in this direction?
Let’s go back to the picture of 1, 2, 3, and 4 blades. So, in the forward case, you need to increase the rotation speed of the rear 3 and 4 blades and reduce the speed of the front blades 1 and 2.
Consequently, the total thrust force and weight remain balanced, making the drone stay at a vertical level.
Additionally, because one of the back blades is spinning clockwise and the other anticlockwise, the high rotation of those propellers create zero angular momentum.
This still applies to the front rotors, hence no rotation. But, the greater force applied to the drone’s rear makes it tilt and move forward.
You agree that each movement happens after changing the spin thrust of one or more propellers.
Why Do Propellers Spin In Different Directions?
Drone propellers spin differently to cancel out the torque. As a result, the main body comes to a stop. Each set of propellers produces torque because it spins and rotates in different directions.
Here are a few things to digest.
You need to understand torque. It’s simply the amount of rotational force. As a vector quantity, the force’s direction also applies.
Still, an additional concept that pops up, in this case, is the action and reaction law of Newton’s third law of motion. A spinning propeller produces torque and creates an equal and opposite force. Thus, the drone body spins together with the propellers.
The torque effect cancels out because, in each rotating propeller, another propeller is also rotating in the opposite direction.
In the end, there’s balance, and you can use your drone efficiently.
How Fast Do Propellers Spin?
Generally, a drone propeller spins at a suitable speed that enables its flight. The average spin rate is 8000rpm, equal to 133 times per second. Still, the drone’s size determines the exact speed of the propeller’s spin.
The engineers can construct the propellers that spin fast enough to produce the required lift with these factors.
I bet you’re wondering if the speed of 8000 rpm is dangerous. Well, yes! High-speed spinning propellers can even cut your skin or cause severe injury.
How Many Propellers Are Ideal for a Drone?
In this bit, I’ll explain the different reactions of drones if they used three propellers. It’s more like answering; can drones fly using three propellers?
No, three propellers can’t fly a drone as required. However, exceptions apply depending on their designs.
Let’s get started;
These are drones that use only three propellers. Usually, most drones use two propellers rotating in opposing directions. So, an additional third propeller stabilizes the drone, making the motor rotate on the axis, avoiding sideways motion.
Cons of three propellers include;
- Difficult to fly
- The third propeller is complex and hard to replace when damaged
- More expensive
Drones with four propellers are the most popular. The common term for these drones in the industry is quadcopters or quadrotors.
There are two clockwise and two counterclockwise propellers in this drone, but all the four propellers rotate at the same speed. Remarkably, operating such a drone is effortless. Besides, replacing these propellers is also easy after damage.
Because of the convenience in the cost and operation of these drones, both professionals and beginners can use them.
But, can these drones use three propellers? No, because there’ll be no balance.
The four propellers should rotate simultaneously to ensure equal thrust and lift forces. But, if one of the blades is inactive, it becomes a flaw in the design.
So, when the drone starts and one of the propellers don’t rotate, it moves sideways and not up. Still, if one of the propellers stops working when the drone is flying, the drone crashes.
The hexacopters are common in heavy drones, especially for use in agriculture. Since each propeller helps lift the drone, more propellers make the lift easier. Consequently, hexacopters lift the drone better than quadcopters.
Can hexacopter fly with three propellers? Three propellers won’t be working hence significantly affecting the drone’s performance. But, if only one fails, the drone can still fly as the damage won’t be significant.
Octocopters are the most powerful uncontrolled aerial drone of all. Typically, drones with eight propellers have a unique design for specific roles, so they have low availability.
Octocopters are big aerial vehicles that can even carry 15kg. More specifically, package delivery companies have been using these drones to offer their services.
Can octocopters fly with three propellers? Having three propellers inactive in this drone doesn’t make it unable to fly. Though the performance won’t be usual, the octocopter still has enough power for a safe landing.
Can A Drone With Broken Propellers Fly?
No, a drone can’t fly with broken propellers. All drones are symmetrical. Therefore if any blade breaks, it causes an imbalance in the overall propeller weight. Still, your drone won’t produce suitable lift or maintain thrust for any motion.
What Should You Do If A Propeller Stops Spinning?
If a propeller stops spinning when the drone is flying, it crashes down. Crashing causes structural damage to the drone. However, there’re preventive measures you could take to reduce the impact, such as;
- Don’t fly your drone close to trees
- Avoid flying in cold temperatures since the cold weakens the propellers
Why Do Propellers Come Angled?
Drone propellers come angled, rotating clockwise and other anticlockwise to ensure the drone doesn’t spin off under the blades. With the propeller spinning, the force from the motor spins as much as to lift the drone.
How Long Should Drone Propellers Last?
The material of propellers determines how long they last. However, it would be best to replace the propellers after three months of continuous use. Also, remember never to use broken propellers or one in bad condition.
Wrapping up, I’m sure you now understand how drone propellers work. Most importantly, drones must have propellers to enable flight.
While propellers mainly work to generate lift, you should know that they only don’t guarantee a flight. Some forces ensure stable flying; thrust and drag and weight and lift.
Still, several factors come into play when choosing a suitable number of propellers for your drone. You want propellers that ensure the drone performs as desired to enjoy the purpose of your drone.
From the above options of propeller numbers, which suits you best and why? Indulge me.