Racing Drone Basics: Learn The Parts To Build Your First Racing Drone

Disclaimer: Racing drones are a blast!  They can also be hard on your wallet.  It is highly recommended that you download the free drone simulator at The Drone Racing League and get some practice on the “sticks” before you invest too much of your hard earned money into a custom drone that you WILL crash.  With that said, LET’S DIG IN!

So you want to build a racing drone and don’t know where to start?  Let’s take care of that by going over the basics.  By the end of this article you should have a good idea of the main components that go into building a racing drone.  

Components

The Bones: Racing Drone Frame

To build a drone, you are going to need a good set of bones….or the frame.  Choosing a frame will dictate nearly every other decision you make when choosing your drone components.

Your budget will also be affected proportionally by the size of drone you decide to build.  Building a smaller drone doesn’t guarantee that your build will be cheaper, but smaller drones and their parts typically cost less.  Also, in the event of a crash a micro drone is more likely to survive due to basic physics principles.  Warning: boring physics reference [Force = Mass x Acceleration].  I think you get the idea!

Micro Drone (50-150mm)
Mini Drone (150mm-250mm)
Full Drone (250mm+)

Although frames come in a wide array of sizes, the most popular racing drone frames range from 80mm to 450mm.  The smaller end of this spectrum would be considered a “Micro” Drone.  Drones between 150mm and 250mm are typically referred to as “Mini” Drones.

  • Key Considerations
    • Dimensions
    • Durability
    • Weight

The dimensions of your drone will depend on the class in which you decide to race.  I plan to touch base on the different racing classes in a future post.

Once you have decided on the dimensions, the game of teeter-totter between weight and durability starts.  Most racing drone frames are made from carbon fiber.  The main difference between frames available on the market is thickness and design.  Thicker frames tend to be stronger, but also heavier.  Many manufacturers provide sufficiently thick frames with sections cut out of the frame to reduce weight.  This allows the manufacturer to make a durable and lightweight frame.

Weight is always a consideration and is listed as a “Key Consideration” on most of the components below.  Although some components don’t add much to the total weight, every gram counts.  You will want to track the combined weight to evaluate the racing drone before purchasing all the parts.

The Brains: Flight Controller (FC)

The Flight Controller is the brain of a racing drone.  It gathers information from sensors and the receiver (explained below) and spits out the signals that control the motors.

  • Key Considerations:
    • Firmware
    • Additional Features
    • Weight

Racing drones should be equipped with a flight controller that can be programmed to adjust the flight characteristics of the drone.  The flight controller is programmed by plugging it into a computer and using software like Betaflight to modify the firmware that is installed on the controller.  Not all flight controllers are compatible with all software versions, so be sure to check out compatibility before buying a flight controller.

Again… weight IS IMPORTANT!



Circulatory System: Power Distribution Board (PDB)

The Power Distribution Board or PDB for short is the component that takes the battery power and distributes it to the various electrical components on the racing drone.

  • Key Considerations
    • Voltage needs of other components
    • Dimensions
    • Weight

The PDB has convertors on board to convert the battery voltage.  For example, it converts the 11 volt battery voltage to the 5 volts needed by the flight controller.  It also distributes the power to each of the four ESCs (discussed next) to free up space on the flight controller.

The dimensions of the PDB are not extremely important, but it does help when deciding how to mount equipment and easily connect to the other components on the frame.  The last thing you want is a component sticking out past the frame becoming a vulnerability during a crash.

Weight: Tiny part, still important

The Heart: Electronic Speed Control (ESC)

The heart that pumps the blood through a racing drone’s system is the electronic speed control or ESC.  The ESC takes in a DC voltage and a PWM (Pulse Width Modulation) signal and turns it into the 3-phase AC output to the motor.

  • Key Considerations
    • Current Output (Amperes)
    • Dimensions
    • Weight

The current output is the largest determining factor when choosing a set of ESCs.  correctly choosing an ESC rating requires you to know the max current draw from your motor.  This information can be found in the motor manufacturer’s Thrust Tables.  

The dimensions should ideally be within the width of the arms of the frame.  Although this is not a requirement, it helps protect the ESCs in the event of a crash.

Weight: Write it down!

The Muscle: Motors

Now for the muscle!  The motors, typically 4 of them, are what get the racing drone across the finish line.  There are two types of motors: Brushed and Brushless.  Racing drones rely on brushless motors due to their high output power compared to their size.  Brushless motors also produce very little heat, require little to no maintenance, and provide more consistent power & performance.

  • Key Considerations:
    • Rotational Speed (KV)
    • Efficiency (watts per gram)
    • Weight

The rotational speed is listed in KV.  This rating tells you the increase in rotational speed, in revolutions per minute (RPM), for every volt applied to the motor.  The resulting speed in RPM is with no load on the motor (i.e. no propeller installed).  Keep in mind that brushless motors SHOULD NOT be operated without a propeller or some kind of load installed.

Let’s look at an example:  One version of the Emax RS2205S motor is rated at 2300KV.  A 3 cell battery (3S) with a voltage of 11.1V will provide 2300KV x 11.1V = 25,530 RPM.  It is important to note that a lower KV rating can produce a faster racing drone.  Let’s assume another motor is rated at 2000KV and can be used with a 5S battery.  It’s max RPM at no load is 2000KV x 18.5V = 37,000 RPM.

The efficiency of the motor we are talking about here is not the amount of power lost versus the power provided to the motor.  What we are talking about is the amount of thrust produced (grams) divided by the power consumption of the motor (watts).  This consideration can help you decide between two capable motors to help increase flight time.

This is where the weight of the drone comes into play.  The combined weight of the racing drone must be less than the thrust that the 4 motors can produce, and that is just enough to get it off the ground.  Ideally, the thrust provided by all 4 motors should be at least 2 times the weight of the drone.  You can shoot for a motor with thrust much higher than 2 times the weight in order to increase the speed of the drone, but at some point the downside of shorter battery life and potentially more difficult throttle controllability come in to play.  Increasing the thrust-to-weight ratio may also require you to upgrade other components.

Recap:  Weight of Complete Drone Assembly x 2 < Thrust Output of Motor = Competitive Racing Drone

The Shovel: Propellers/Blades

Suppose you need to dig a trench.  You need a shovel, right?  Ok… I am assuming you don’t have a trencher in your garage!  Propellers are the shovels that complement the muscle behind them.   Without a good shovel meant for digging, it won’t matter how much muscle you have behind it.  The same concept applies to the motor/blade combination.  Propellers are classified by their length, pitch(twist of the blade), and number of blades.

Example 1:  The Lumineier 5x4x3 is a 5″ long, 4″ pitch, 3 blade propeller.

Example 2:  The DYS XT5550-2 blade is a 5.5″ long, 5″ pitch, 2 blade propeller.

  • Key Considerations
    • Motor Compatibility
    • Length
    • Weight

Most manufacturers of motors have handy Motor Thrust Tables that show the different thrust output you can get from each motor with different propellers.  It is best to stick with a blade size and pitch that is recommended in their table.

The length of the propellers are also restricted by the size of frame you choose.  All frames SHOULD have documentation stating the max size of propeller that will work with them.  Keep this in mind when choosing your propellers.

Weight…again.

The Food/Fuel: LiPo Battery

The food that fuels the “body” of the racing drone is the battery.  The type of battery used for Racing drones are LiPo or Lithium Ion Polymer.  LiPo batteries are capable of producing a lot of current and are very small considering their milliampere-hour ratings (mAH).

  • Key Considerations:
    • Voltage Required by Other Components
    • Capacity (mAH)
    • Discharge Rate (C)
    • Weight

The voltage of your battery will mostly be dependent on the voltage required by the motor and ESC.

The mAH of the battery tells you how much current the battery can supply for one hour.  If your drone consumes power at twice the amount of current that is listed on the battery, you can fly for half the amount of time.

For example:  A 1500mAH battery is the equivalent to a 1.5AH battery.  If a drones constant current required is 4.5 amperes, or 3 times the rated current, the battery should last for 20 minutes.

The other consideration is discharge rate.  A racing drone demands a large amount of current to keep those propellers spinning during a race.  The discharge rate expressed with a number followed by the letter “C” determines how much current can be continuously supplied by the battery.

Example:  We will use the same 1500mAH (1.5AH) battery and add a discharge rating of 10C.  This means that the battery can constantly supply 1.5AH x 10C = 15 Amps.

For demonstration purposes let’s assume that the drone DOES draw a continuous 15 Amps from this battery.  That means that it is using 10 times the 1.5AH rating and will go through the battery in 1/10th of an hour, or 6 minutes.  You can now see how choosing the correct battery plays a big role in the performance and run-time of a racing drone.

 

The Eyes: FPV Camera & VTX

Racing drones are not meant to fly without First Person View (FPV).  The courses are large and there is no way that you can run around chasing a racing drone to determine where to fly next.  That is why racing drones are given eyes!  It all starts with the FPV camera and a Video Transmitter (VTx).

  • Key Considerations
    • Video Quality
    • Signal Transmission Strength
    • Weight

The camera used to capture flight video needs to be clear enough to make sure you don’t hit a small branch sticking off a tree.  Although, keep in mind that cameras with better picture quality will cost relatively more money or add weight to your racing drone.  Also keep in mind that the
picture quality is only as good as the picture displayed by the FPV goggles (discussed below) you have.

The signal strength dictates how far the racing drone can fly before the video feed starts to cut out.  This is a VERY important consideration.  Flying further than the VTx can accomodate will almost certainly end in a bad crash.  Like I said before, without eyes makes for a difficult flight.

The Eyes Part 2: FPV Goggles

A set of FPV goggles or a monitor is the tool needed for you to see what the onboard camera is seeing.  The FPV goggles have a receiver (VRx) that “captures” the 5.8GHz signal sent out by the VTx.  That signal is then converted into the display of the FPV goggles or monitor.

  • Key Considerations
    • Video Quality
    • Size
    • DVR

FPV goggles range in price of $40 to more than $500.  The price is typically based on video quality and the physical size of the unit.  Your best bet is to purchase the nicest headset that you can afford because it will likely stick with you through many drones.




One bit of functionality that isn’t always included in a FPV goggle headset is DVR.  The benefit of DVR is that you can record the video being captured by the onboard camera and view it later (or showoff to your friends).  This is especially beneficial on smaller drones where you can’t place a GoPro Session (or similar) onboard due to the weight it adds to the racing drone.

Transmitter (Tx)

The final two items have a less prominent role in deciding how to build your racing drone.  The transmitter, or controller, is the component that sends a 2.4GHz signal to the Racing drone based on the pilots actions.

  • Key Considerations
    • 2.4GHz
    • # of Drones
    • Additional sensors

One thing you will want to be sure of when buying a transmitter is that it is 2.4GHz.  2.4GHz is the standard for racing drones due to its flexibility and wide frequency band.  Without getting into the details, this is helpful when you get to the track.

Many pilots like to have a transmitter that can store multiple receivers at the same time.  This allows you to switch to additional drones without going through the setup every time you want to make the switch.  Most transmitters come with the option to have at least a few drones memorized in its settings.

If you plan to add additional sensors/controls, you will need a transmitter with more than 4 channels.  The bare essentials that are needed for a racing drone are Throttle, Pitch, Yaw, and Roll.  Any additional functionality like turning on or off LED lights would require additional channels.  Most transmitters come with 4 to 9 channels.

Receiver (Rx)

The receiver is the component installed on the racing drone that receives the 2.4GHz signal from the transmitter.  This signal is relayed to the flight controller and subsequently controls the racing drone.

  • Key Considerations
    • Compatibility with Tx
    • Weight

The most important thing to remember with the receiver is that it is compatible with your transmitter.  Transmitters are only designed to work with their respective receiver and vice versa.

Since the receiver is installed on the drone, you will want to note the weight. 😉


Recap:

I think I drove it home with all the references to weight in the “Key Considerations” sections.  The weight of each component in a racing drone is important due to the fact that we want these things to fly and we want them to fly fast!

The greatest part about building your own racing drone is that you have the opportunity to optimize the speed and controllability along the way.  Put a little extra time in the planning stages and you will see a big difference in the performance.

I hope this explanation of what goes into a racing drone was beneficial.  Now get out there, build a racing drone, and start piloting a four rotor rocket!

2 thoughts on “Racing Drone Basics: Learn The Parts To Build Your First Racing Drone”

  1. Very informative, especially for a newbie like myself. I had the opportunity to “fly” a racing drone vicariously using FPV goggles at a racing event in Lincoln, NB. I was hooked! I’ve been scouring the web for info on what I’d need to get started building my own drone. Your article was (is) a huge help. One thing I noticed missing was discussion of the need for a flight controller configurator. Anyway, after reading your article, I’m ready to get started.

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