The Essentials of Drone Building
‘Take care of your car in the garage, and the car will take care of you on the road.’
In the last blog, you got a concise understanding of the basic concept and different components of a drone, as well as a brief account on the substantial and far-flung applications it potentially possesses. You were introduced to a few terms that are foundational in the mechanical and aerodynamic aspects of drone structure and function. In this blog, we’re gonna be looking at drones from a more in-depth angle at the structural parameters. So without further ado, let’s get right on board!
Motors
It goes without saying, and little imagination, those motors are the chief functional components of a drone. Motors come in a diverse range of sizes, shapes and specifications and it is beyond the scope of a single blog or article to talk about them all. Hence, we’ll be looking at motors specifically in the context of drone building. If you feel you need to revisit a few fundamentals from electromagnetic induction and basic science of motors so that you can get a better hold of the topics examined here, then please do so.
We’ll talk about how to get started; motors, BLDC motors in particular; ESCs and develop a rough but sufficient background understanding of the science and working principles behind them. We will be looking at the whole domain through the vision of drone building in a semi-technical and user-friendly DIY manner.
Enjoy as we prepare you for your coronation to the Drone Throne!
Let The Drones Begin!
In the previous blog of this series, there was an exhaustive list of structural components mentioned that go into the making of a drone. Most of these are available online at very decent prices and you shouldn’t face any difficulty in procuring resources insofar as materials are concerned. However, for understanding the build process and the principles behind different parts and how they assimilate together to form a drone: hmm, that’s why we’re in the scheme of things here.
Let’s go down a motor ride! And yes: we’re talkin’ real motors.
Demystifying BLDC motors and understanding what they’re all about
In brief, we will help you grasp the dynamics behind brushless drone motor used for drones and how they influence flight characteristics. We’ll have a look into types of motors, weight, design variations, total power and factors affecting a quad motor performance.
For beginners, there are 2 types of motors used in drones: brushed and brushless motors. They’re different in the way they operate. The brushless is significantly more powerful for their weight than brushed motors, and they last way longer. For larger drones: brushless is the gold standard.
Why Brushless Motors?
Brushless motors are as effective for high –speed operation as a brushed motor, and because there are no brushes to replace, a brushless can have a life expectancy more than about 10,000 hours.
So, why BLDC again?
- High-Speed Operation — A BLDC motor can operate at speeds above 10,000 rpm under loaded and unloaded conditions.
- Responsiveness as well as Quick Acceleration — Inner rotor Brushless DC motors have low rotor inertia, allowing them to accelerate, decelerate, and reverse direction quickly.
- High Power Density — BLDC motors have the highest running torque per cubic inch of any DC motor.
- High Reliability — BLDC motors do not have brushes, meaning they are more reliable and have life expectancies of over 10,000 hours.
Performance Factors
Thrust to Weight Ratio
A thumb rule is that the motors should be able to provide twice as much thrust as the total weight of the quad. If the thrust provided by the motors is too little, the drone will not react well to your control and may experience issues on takeoff. For more, refer the standard motor size chart depending on your drone.
KV — Velocity Constant
Theoretically, KV represents the rotations per minute at which the motor rotates for every volt applied to the motor. Higher the KV means lower resistance and higher current draw and lower efficiencies. Lower KV means higher resistance and lower current draw and considerably better efficiencies. If you’re starting somewhere around 1000KV would be preferable.
Torque
Moving on the next factor that comes into picture is the torque produced by the motor. Torque is the spinning force or the rotatory force that spins the propeller. It doesn’t matter much if you’re starting.
Current Draw
Current drawn by the motor is important because it helps us to determine the drone ESC size required for that particular motor. To understand this, we need to have a look at ESCs or Electronic Speed Controllers.
Brace yourselves for another technical turnabout.
Enter Electronic Speed Controllers, aka ESCs
An Electronic Speed Controller (ESC) is an electronic circuit that acts as the interface between the pilot’s commands and the individual drone motors. There are several types of ESCs in the market, but brushless motors require a 3-phase ESC. These are easily distinguished by the presence of three soldering pads that are meant to connect to the three motor phases of a brushless motor.
In selecting an ESC, it is important to think about three principle considerations.
- Current Rating: The current rating will greatly dictate the amount of amperage your ESC must be able to handle. Rule of thumb to select ESC current rating is, it should be 1.5 times the maximum current draw.
- Propeller: Choice of propeller will also dictate what amp rating your ESC should be. Will your drone be spinning 3, 4, 5, or 6-inch propellers? What kind of performance will you want, and therefore what kind of propeller pitch will you use?
- Voltage: Will you be using a 3 cell battery, or a 4, 5 or even 6 cell battery? ESCs are rated for amperage, along with battery cells.
There are many choices of ESC to meet the needs of many types of drones, from small 2-inch drones, to power-hungry racing drones, to longer-range camera drones. It is important to match the ESC with the style of flying and intended application. However, it is better to get an ESC capable of handling greater amps and voltage than you may plan to use, as you may give yourself room to grow, along with a margin of safety.
So to say, we have…
- Delved into a comprehensive insight on BLDC motors; their build, operation, advantages, factors and variability;
- Understood and briefly capitulated on what an ESC is and the factors to be kept in mind while choosing it;
- Developed a thorough and solid background to start with the next process in drone building: Flight Controllers.
Next up, we have our informative and enriching blog on the science and the art of flight controllers, Lithium Polymer batteries, and selective terminology.
Be safe, learn, innovate, and aspire to soar!
