Introduction: DIY Modular & Transformable FPV Racing Quadcopter!

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About: I always loved making things since I was a kid! I currently make a lot of DIY drones and love 3D printing! I'm also into skateboarding, motorcycles, electronics or anything that can be home made :)

Most of quadcopters, especially FPV racing quads always looks the same: they are X or H shaped, with motor on facing up.

I wanted to create a FPV racing drone that didn't look like all the other quads and moreover, that is transformable into multiple different style of drones !

In this Instructable you'll learn how to easily create a Modular FPV Racing drone that can be transformed into more than 8 styles with a single frame!!

YES! 8 styles with a single frame including:

- Basic X shape, normal OR inverted motors

- Pendulum X Shape, motors on top, normal OR inverted

- Uncommon "+" Shape, normal OR inverted motors

- Uncommon Pendulum "+" Shape, normal OR inverted motors

Then each of those 8 frame styles can be customized with: batteries on bottom or on top, landing gear or no landing gear etc...

Which make more than 30 variants on a single frame !

Tools needed:

- 3D printer or 3D Hubs account or laser cutting machine.

- Soldering iron

- Screwdrivers (HEX 2.0mm)

Hardware: M3 Bolts (10mm length)

Electronics parts list is located in step 3

Difficulty: Easy to Medium, no skills required except basic soldering

Building time: about 4 hours then 30 min every time you want to change your frame style!

Step 1: Print the 3 Frame Pieces!

The first step is to get the 3 pieces of frame I designed and that will allow you to create your drone.

I have including all the STL files at the end of the Instructable.

The main, central plate will fit on any printer with a 200mm x 200mm print bed, but I also designed a version with detachable arm that can be printed on a very small print bed of only 80mm x 80mm !

Note that the "Top plate" comes in 2 version: one with a inclined area for mounting a GoPro and a standard, flat top plate.

You have 3 options to get the pieces of frame:

  1. Print them yourself, it prints pretty quickly
  2. Print them via 3DHubs, you should have the 3 pieces for about $5
  3. Laser cut them in a strong material of your choice (aluminium? acrylic? carbon??)

Now, for 3D printing the parts, here are my recommendations on Filaments and Infill:

Use a strong filament, like PETG or ABS, that will have a little amount of flexibility which mean that in the case of a crash, it will flex instead of breaking, I printed mine in PETG.

PLA will also work, it will even have an advantage: the frame will be very stiff so it will be more efficient to handle the thrust of the motors! However, it will be more likely to break in the event of a crash.

Infill:
As for infill density, you'll want to have a drone that won't break easily, so it is best to use higher infills (50% or more) so it will be stronger.. It will be a little heavier but the motors we'll use won't have any problem lifting it. What I did is print the 3 pieces at a 65% infill. You can do more, like 90% for maximum strength, if you are using PLA I recommend at least a 80% infill.

As a reminder for the Filaments, here are my tips on PLA, ABS and PETG:

- PLA :The easier filament to print with. The main advantage is that it prints easily and it is pretty stiff, so the frame will be stiffer and won't bend with the thrust of the motors. However it will break more easily than ABS or PETG when crashing.

- ABS : The advantage of ABS is that it is stronger than PLA, it is also a bit more flexible so it won't break as easily as PLA in case of a crash. However it is more difficult to print, and not everyone is equipped to print ABS.

- PETG : An alternative to ABS, PETG is stronger than PLA and is also a little flexible, which means that your frame will not break easily. It is also pretty easy to print with and it is non toxic.

Check out the Torture test video I made with the frame I printed in PETG! as you can see, is it pretty strong :)

There are also new filaments like POM which seems even stronger but requires high printing temperatures.

Step 2: Assemble the Frame As You Like!

Now, the fun part! :)

Hardware required:

- M3 bolts

- M3 standoffs, or 3D printed standoff (I have included the STL file)

It is now time to assemble your Racing drone as you want to!!

You can first choose your shape: X or + Shape.

X shape means that you have 2 front arms and motors and 2 back arms and motors.

+ Shape means that you have 1 front arm and motor, 2 laterals arms and motors and 1 back motor

If you are choosing an X shape, you have to mount the Flight controller in diagonal, if you are choosing a + shape, just mount it in the line of an arm.

There are many theories about + vs X shapes, but overall, the performance will be about the same, most of racing drone nowadays are X shape to avoid having a front propeller in front of the FPV camera, but if you mount the camera on top, you'll be fine.

Choose the direction of your motors: facing up (normal) or down (inverted) !

Now, you can choose wether you want your motors to be facing up, like 99% of FPV racing drone, or facing down (be the 1% different!!)

In terms of pure theoretical performance, motors facing down will be a little more efficient!

Why? because the vortex (airflow) created by the propellers will go straight down, without hitting the arm on a small area. This may be negligible, but in theory, as the air on the exhaust of the propellers is faster than the one on the intake, having the arms on the intake (motors facing down) makes the motors and propellers more efficient!

Choose where to mount the main frame & arms: on top or bottom!

Now it's time to choose if you want your main frame piece (with the arms) on the bottom (below the electronics and body) or on top (above the electronics and body, this is a "Pendulum" configuration)

A pendulum configuration will tend to be more stable, also more original :)

So it has it pros and cons depending on what you want to do: for freestyle and accro flying it might not be the most agile configuration, but for fast racing it can have it perks.

Choose the other accessories:

I have designed and included various optional plates such as a bottom plate, where you can insert a battery or just use as landing skids and also 2 differents top plates if you plan to mount a gopro or not.

You can choose to mount the battery on bottom or on top. Same for the electronics.

Step 3: Add the Electronics!

You now have to add the electronics needed to fly but don't worry ! it is not as difficult as it seems, it is actually
pretty easy if you know how to solder (that's all you have to know but it can be learned easily:) ).

You can get all the parts from online stores like Banggood, eBay, Hobbyking, Aliexpress, Gearbest and other Drone shops.

List of parts needed and recommendations:

- 4 x 1806 motors - Prices start at $7 per motor - Smaller 1306 size or bigger 2204 motors might fit too but you'll have to drill new mounting holes. I recommend the DYS 1806 motors for best performances but any 1806 motors will work. I actually got 4 cheap 1806 motors from Aliexpress and they work just fine!

- 4 x ESC - Starts at $5 per ESC - The Electronic Speed Controller will control the speed of the motors, you'll want to choose at least 12A ESC, 20A ESC would be the best. They are 2 main firmwares for multirotor ESCs : SimonK and BL Heli. I highly recommend BL Heli ESC with BL Heli bootloader because they are a lot easier to program. On this drone, I used KingKong 12A BL heli ESCs because I had some laying around but the best ESC in my opinion if you're willing to pay $11 per ESC are Favorite Littlebee 20A ESCs.

- Flight Controller - Starts at $13 - The brain of your drone. For this drone, you'll need either Naze32 or CC3D flight controller. I personally prefer and recommend Naze32 because they have more options for configuration but both will work. It will be also quicker to change configuration from X shape to + shape with the Naze. Naze32 also allows you to program the ESCs if directly through the flight controller which is very usefull. The software to use with Naze32 flight controllers are either CleanFlight, BaseFlight or BetaFlight (all free) and CC3D will use OpenPilot (free too). I used a Naze 32 Rev 6 flight controller I got for $13 from Banggood.

- (Optional) Power Distribution Board or BEC - starts at $3 - A power distribution is actually not mandatory, but is recommended for a clean setup, it will distribute power from battery to the ESCs, flight controller, camera, VTX etc... PDBs have BEC integrated which means they'll have a 5v output somewhere to power up the Flight controller. Note that your ESC might have integrated BECs to power up the flight controller, but most of the performance ESC are OPTO which means they don't have BECs. If you have OPTO escs and decide not to use a PDB. You'll need a 5V BEC to power up the flight controller. Link to some PDBs.

- A Radio & receiver - Starting at $50 - This might be the more expensive part, although you might already have you if you're an RC enthusiast. Make sure that your radio have at least 6 channel and a PPM / CPPM receiver, which is much more convenient than standard PWM receivers. I use a FlySky Fs i6 with a ia6B receiver, the package cost around $50 and it is a really great and cheap radio. I actually prefer it to some very expensive Taranis I have too. FlySky FS i6 radio + receiver

- Battery Cable & connector - $2 - To be connected to your PDB, the most common connector for baterry is a XT60 male. For the cable, choose a cable that is not to thin and will easily handle twice or more the max voltage of your battery.

- A camera & 5.8 Ghz Video transmitter (optional) - Starting at $15 for camera & $12 for VTX) - If you want to fly in FPV, then you'll need a camera and 5.8Ghz VTX. There are a lot of different cameras, CMOS, CCD, 600 to 1000 TVL etc... the choice will be up to you. There are also a lot of different size. My favourite camera is the FatShark 700 TVL although it cost $30 and is far from being the cheapest (many cost $10) but it gives a great clear image and is very reliable. For the VTX, the best one in my opinion in the Skyzone 200mw 5.8 VTX, it cost $12 and works really great, it is also pretty small. Note that camera/vtx combo also exist for around 30$ and in a super small size. Don't forget the antennas if you go with a FPV drone, you'll also need some FPV googles or monitor and a receiver of course. You can have very descent quality googles + receiver for $70 now ! Link to some cameras examples.

- Propellers - starting at $2 for 4 props - The propellers I recommend and the one I use are the DAL prop, either the DAL bullnose or DAL V2 props, both 2 blades and 3 blades version. They are almost unbreakable and will hold a ton of thrust. Link to DAL Props.

- Hardware - $1 - In order to mount the Flight Controller and Power distribution board (if you have one) to your frame, Plastic M3 screws & nuts can be very handful. They are better than metal ones because they won't create any short circuit on the electronics. A full box of more than 180 plastic M3 screws and nuts can be purchased for $5 on ebay. Installation & wiring (Picture 1)

Once you got all the components needed, you just have to put everything together ! and it is almost as simple as plug & play ! This wiring diagram will help you to see how you should connect everything together but I will also describe the connection in bullet points :

- Battery wire to PDB battery input

- Motors wire to ESC: there are 3 motors wire to be connected on the ESC, how you connect the wires does not matter, it will only affect the rotation sens of the motor, but this can be change when programming the ESC if you have a BL Heli boot-loaded Esc

- 4 ESC positive to PDB (or battery, although not recommended) positive and 4 ESC negative to PDB negative.

- 4 ESC signal to Flight controler motor output 1 2 3 4 signal. The order of the motors will depend of your flight controller, a motor number diagram will be available on the software of your FC (Openpilot, Cleanflight etc...)

- PDB 5V output to Flight controller, the 5V input on the FC is actually on the motor output (6 of them) pins. So just choose a pin to connect the 5V input.

- Flight controller, Positive (5v), negative and PPM (Ch 1) Signal to Receiver.

- PDB 5V output to your camera

- PDB 12V or more (depending on your VTX) output to your VTX. - Camera Signal to your VTX Thats it ! it's all you need to fly !

Recommendation: do as much direct soldering as possible, that is to say avoid unnecessary connectors, they will be a potential point of failure and take up a lot of space especially on smaller frames.

Step 4: Configure the Drone With Your PC

Since there are many different configurations, you'll need to connect your drone to your PC to configure it, but don't worry, it is super easy!

The first thing to do once connected will be to choose a "X" or "+" shape on your Flight Controller depending on what you chose and set the motor rotation of each motor according to the drawing.

Software

Before explaining how to configure your Flight controller according to the type of your frame, I'll give you a brief reminder on softwares you have to download:

Depending on your flight controller you'll need to download one of these software, but again, I recommend using a Naze32:
For Naze32 : Cleanflight (Chrome Extension) or BaseFlight (Chrome Extension) or BetaFlight.To connect your Naze32 to your PC you'll need a micro USB cable

For CC3D : OpenPilot (Make sure to download a release supporting CC3D) Most of CC3D board use mini usb cables, but newest ones might have micro usb slots.

Driver: For both Flight controllers, you'll a need to driver that will recognize the FC when connected to your PC, here it is: USB to UART driver

Configuration

Now, I will make a tutorial on Cleanflight, I will assume that your Flight Controller is already flashed with the latest version of Cleanflight, if you don't how to do it, you can read my previous instructable here where it is explained.

Once you have connected your drone to your PC via the USB cable, open CleanFlight and click on "Connect", then head on the "Configuration" Tab.

Now, in the "Mixer" area, you'll have to chose the frame type of your drone, choose either "Quad +" or "Quad X" depending on how you mounted your drone.

This is practicaly the only thing you have to do! :) You can also go further into your configuration by tuning your PIDs but this is already a very advanced step of configuration that is not mandatory for flying at all.

Once you've selected the frame shape, a diagram showing the rotation sense of each motor will show up, make sure that all of your motors turn in the right direction, I will now explain how to check this.

Motor rotation sense

Before testing a motor, MAKE SURE THAT THE PROPELLERS ARE REMOVED.

Spining propellers can be very dangerous so make sure that you have removed them before this step.

To test the rotation direction of a motor, head onto the "Motors" tab, plug a battery in your drone and then test each motor by moving the little knob and check if the rotation of each motor is the same as the one on the diagram and that it's not inverted.

If some motors spin in the wrong direction, just note their number so we'll be able to change this when programming the ESC.

Make sure that you have your quad poiting in the right direction (it's nose facing forward) when testing each motor and also note that if you have inverted motor, it doesn't change. What is important is in which direction each motor spin when looking from the top of drone, no matter in which way the motors are mounted.

Programming the ESCs.

For this step, you'll need to download BL Heli Suite.

Programming the ESC will allow you to easily change the spinning direction of a motor.

If you have a Naze32 like me, you don't need special programming cables ! just plug your FC with the USB cable, open BL Heli Suite and in the "Select ATMEL/SILABS interface" tab, choose "SILABS BLHeLi bootloader (CleanFlight). Then just click connect and you'll be good to go !

As I said, programming the ESC is usefull to reverse a motor direction without having to swap the already soldered cable between the ESC and the motor.

To do so, just select the motor you wish to program by unselecting all the others on the little squares at the bottom of the screen. Then, in the "Motor direction" area, choose "Inverted" instead of "normal".

If you want more information on ESC programming, there are many tutorials here.

Final configuration

Now, let's go back to CleanFlight for the final steps of the configuration. Theses step will be up to your personal preferences but here are few recommendations.

It can be useful to program few Flight modes, by default, the Naze32 on cleanflight is in accro mode, so adding a stabilized mode (angle or horizon) for takeoff or landings can be useful.

I also chose to add an air mode, but you could choose to arm your drone with a switch too for example.

Finally, once your configuration is done, head back to the main tab and calibrate your accelerometer by placing your quadcopter on a level surface and pressing "Calibrate accelerometer".

Step 5: Have Fun Flying an Uncommon Drone!

There you go you are now ready to fly! :)

You can have fun trying one frame configuration then change it after few flights to see which configuration you prefer!

Make sure to post photos of your build in the comments :)

IMPORTANT:
Please, always fly legally and always check for your specific country regulations (FAA for example). Such drones can be very dangerous (cutting propellers and high capable of reaching high speeds) and can easily harm people or cause property damage if not used correctly. Always fly safely, away from people, habitations or animals.

If you like my Instructable, drone design, or find any step useful, please vote for me in the Make it fly contest :)

Please note that the design and idea of this modular frame is licensed under the Creative Commons.

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