PVC Octocopter Drone Frame With Folding Arms

My first instructable - thanks for taking the time to view!

Let me start with a disclaimer: this project is for a very large drone with 8 powerful motors. If you fly this drone publicly you will likely be breaking some laws (at least in Canada or the US) unless you are a professionally licensed drone pilot. More importantly, you will basically be putting a lawnmower up into the sky. Nobody wants a lawnmower flying over their head! Please be very careful!

I built this drone as a "proof of concept" more than anything else. I wanted to find out if pvc would be an acceptable material for a drone frame. I started making home-built drones just after the beginning of the Covid pandemic - probably like many of you I needed something to distract me and keep my brain working. My first was a simple 680 mm hexacopter, big enough to carry a GoPro camera. But I want bigger, and big commercially made drone frames are really expensive (for a good reason - carbon fiber is a superior material, just out of my budget at the time).

The final build is just over a meter in diameter from motor center to motor center. It's heavy, but the 8 motors and BIG battery lift it easily, with plenty of thrust to add a small mirrorless or digital SLR camera, or a small 4K video camera with a gimbal.

All of the frame parts and wiring are available on Amazon or Formufit (full disclosure - I'm not being paid or sponsored by either company). The electronics and other parts can be found on Amazon or eBay. The motors I used are somewhat expensive new, but I found some used ones on eBay for a great price.

Hope you have fun - and share your builds!

It's a pretty long list! Most of the parts are not too expensive, but the motors are pricey, so please shop around! I found mine used on eBay for about $200 for all 8 (new is $96 each).

1. Frame pieces (all pvc is from Formufit.com - most is also available on Amazon.com. Colors are your choice.)

• 3/4" pvc pipe (12 feet) (black)
• 3/4" pvc pipe (5 feet) (white)
• 3/4" pvc 45-degree elbow (8) (black)
• 3/4" pvc tee (8) (black)
• 3/4" pvc cross connector (4) (black)
• 3/4" pvc 4-way connector (4) (black)
• 3/4" pvc 5-way connector (1) (black)
• 3/4" pvc end cap (12) (black)
• 1" pvc end cap (8) (black)
• 4" pvc pipe clamp for 1" pipe (8) (black)
• 3/4" pvc inline folding coupling (8) (black)
• 1/8" carbon fiber plate (2) (6" x 4")
• 1/8" carbon fiber plate (1) (4" x 4")

2. Drive and electronics

• Brushless motors (8) (T-Motor MN4010 400 KV)
• Folding propellers (8) (T-Motor 16.2" length x 5.3" pitch)
• Electronic speed controllers (8) (T-Motor 40 amp)
• Power distribution board (1) (300 amp octocopter PDB with 3.5 mm plugs)
• Flight controller (1) (I used a DJI Naza-M V2)
• Radio controller and receiver (I use a Jumper T8SG controller with a Turnigy TGY-iA6C receiver)
• 6S 22.2-volt LiPo battery (1) (I used a TCBWorth 22,000 mAh battery)
• 14 gauge wire (8 colors, about 10 feet of each color)
• 3-pole bullet connector pairs female (8) (MT-60 3.5 mm)
• 3.5 mm bullet connectors male (40)

3. Miscellaneous stuff

• 3/8" to 1/4" adapter screw (8)
• 1/4" D-ring camera screw (8)
• M4 x 8 mm thumb screw (16)
• 50mm (approx. 2") standoffs (4) (to fit 2.5 mm screws)
• 25mm (approx. 1") standoffs (4) to fit 2.5 mm screws)
• 2.5 mm hex-head screws (about 20)
• Small screws (16) (#12 pan-head 1/4")
• Small flathead screws (I bought a 100-pack #2-56 1/4" length from Amazon)
• 3M double-sided sticky pads (4) (40mm x 40mm)

You have a choice - you could build your drone frame first, and then find motors to fit. However, since motors are the most expensive individual item in this build, and my experience is that it's worth getting quality motors, I suggest getting motors and propellers first and then building the smallest drone frame to fit.

This instructable isn't about drone motors, but in case you wish to educate yourself, here's a link to Drone Nodes. It's all explained in here, so I won't go into thrust-to-weight ratio or kv values. You're looking for reasonably powerful motors (thrust around 3-4 kg per motor at 100% power) because using pvc means your drone frame will be heavier than a comparable carbon fiber, glass fiber, or aluminum frame. But it will also be way cheaper - for comparison, the carbon fiber and aluminum Tarot IRON MAN 1000 is $365 on Amazon.

The motor I used, and highly recommend if you can source it at a good price, is the T-Motor MN4014 400KV (about $96 new). I found a great deal on eBay and got all 8 motors for $200 (lightly used). Another motor I would like to try is the Turnigy Aerodrive SK3 - 5045-450KV brushless motor, for about $55 new on Hobbyking.

Once you have the motors, you will need propellers (4 clockwise rotation and 4 counterclockwise rotation). Be sure that your motors and propellers are compatible - the shaft size/bolt hole pattern needs to be a match, and your propellers should be a suitable length for the motor. For the motors I mentioned above, 16 inch propellers are a good fit and maximize the thrust of my motors. You can usually find a spec sheet for your motor on the seller's page, which will give you an idea of thrust, power usage, and efficiency for various motor-propeller combinations. My propellers, the T-Motor 16.2/5.3 are very well matched to my motors. Another great source for high quality propellers is Master Airscrew.

Once you have the motors and propellers, you can plan out the size of your octocopter drone. Your will want it to be just large enough to accommodate your drive system. Here's a great calculator to help you figure this out: the octagon calculator.

For my drone, with 16.2 inch propellers, the minimum size necessary for 8 propellers arranged in a circle was 1075.2 mm (42.33") from one propeller center to the opposite propeller center. Giving a little clearance, I settled on a frame of 1100 mm (43.3").

Note: you will need to get comfortable working in both imperial and metric with drone building. I'm using metric in this instructable, except where the product measurements are in imperial units (e.g. pvc pipe diameters and propeller length).

The center ring provides the drone frame with it's strength and supports the arms.

Parts:

• center member: 3/4" pvc 5-way connector
• outer ring:
  • 3/4" pvc 45-degree elbows (8)
  • 3/4" pvc cross connector (4)
  • 3/4" pvc 4-way connector (4)
  • 3/4" pvc pipe (16 pieces each 2" for connecting other components)
• 3/4" pvc pipe (4 pieces each 6.5" for connecting the outer ring to the center member)
• Small flathead screws (#2-56 1/4" length) to connect the pvc elements to each other

Steps:

1. Create the center member:
   Connect each of the 6.5" pvc pipe lengths to the the 5-way connector, leaving the top hole open. Set this aside.
2. Create the ring:
   Connect the pvc pieces together in this order to make a small octagon:
   45-degree elbow --> short pipe length --> cross connector --> short pipe length --> 45-degree elbow --> short pipe length --> 4-way connector --> short pipe length --> 45-degree elbow --> short pipe length --> cross connector --> short pipe length --> 45-degree elbow --> short pipe length --> 4-way connector --> short pipe length --> 45-degree elbow --> short pipe length --> cross connector --> short pipe length --> 45-degree elbow --> short pipe length --> 4-way connector --> short pipe length --> 45-degree elbow --> short pipe length --> cross connector --> short pipe length --> 45-degree elbow --> short pipe length --> 4-way connector --> short pipe length
3. Connect the outer ring to the center member to complete the inner frame. This may take a little "bending and forcing", but the pvc pipe still has a small amount of flex at this size.
4. Make sure the center ring is perfectly flat, and secure the pieces using the small flathead screws, 2 at each joint.

Note: It's entirely OK to use pvc cement to connect these pieces together, but I used small flathead screws in case I wanted to take this apart later. The pipes fit tightly into the other pieces, and the small screws just keep them from pulling apart.

We'll talk more about wiring the drone later, but at this point you should run the motor wires from the center of the frame through the tubing, as it will be much more difficult after you add the arms in the next step.

You will need three wires for each motor. I used 14 gauge multi-strand copper wire with silicon insulation. You might find it helpful to use different colored wires for each motor, as you will want to keep track when you connect the electronics together. Make sure your wires are long enough to reach to the end of the arms, with about 6" left over at each end.

The arms extend from the center to create a frame with a diameter of about 110 cm (or 43"). This is an awkward size for transporting in most vehicles, so I decided I wanted the arms to fold. I managed this with a few specialty pvc pieces: folding couplings and pipe clamps. The folding couplings allow the arms of the drone to fold downwards, shortening the width of the drone from 110 cm to about half of that, allowing it to fit easily into the trunk of a car. The pipe clamps secure to the folding coupling with D-ring camera screws, which can be easily removed for folding and reinserted for assembly.

I made 5 arms with black pvc pipe, and 3 arms with white pipe. The reason for using two colors is that the white arms will be at the back of the drone, and will be very visible from the ground. I will be able to tell what the orientation of the drone is, at least when I am reasonably close to it.

Parts:

• 4" pvc pipe clamp for 1" pipe (8) (black)
• 3/4" pvc inline folding coupling (8) (black)
• 3/4" pvc pipe (5) (black, 12.5" long - adjust to fit your drone size)
• 3/4" pvc pipe (3) (white, 12.5" long - adjust to fit your drone size)
• 3/4" pvc pipe (8 pieces each 2" for connecting the arms to the center ring)
• 3/8" to 1/4" adapter screw (8)
• 1/4" D-ring camera screw (8)
• M4 x 8 mm thumb screw (8)

Steps:

1. Connect the drone arm (12.5" pvc pipe) to the folding coupling, pushing it all the way in.
2. Connect the short (2") pipe to the other end of the coupling.
3. Place the pipe clamp over the coupling, flush with the end of the short pipe.
4. Drill a 5/16" hole through the pipe clamp, coupling, and long pipe (arm) for the D-ring camera screw.
5. Drill a 1/8" hole through the pipe clamp, coupling, and short pipe for the thumb screw.
6. Remove the pipe clamp, and using a 3/8" - 16 tap, tap the hole for the D-ring camera screw.
7. Screw the insert so that it goes through the coupling and into the arm - this will secure the arm to the coupling.
8. Place the pipe clamp back on, and attach it to the folding coupling with the D-ring adapter screw and the 1/8" thumb screw.

Steps:

1. Before connecting the arms to the center ring, you will need to run the motor wires through the arms. If the motor wires are too short, now is a good time to go back to Step 4 and run longer wires through the center ring.
2. Push the short 3/4" pipe on the drone arm into the center ring. Drill a 1/8 inch hole through the pipe clamp and into the center ring. Secure it with a 1/8' thumb screw.
3. Repeat this for all 8 arms, placing the 3 white arms together as in the photo above. To fold the arms, remove the D-ring screw from each and bend the arm downwards.

The motor mount bracket serves a dual purpose - it attaches the motors to the frame of the drone, and it extends downward to provide legs to support the drone off the ground.

Parts:

• 3/4" pvc tee (8) (black)
• 3/4" pvc end cap (8) (black)
• 1" pvc end cap (8) (black)
• 3/4" pvc pipe (8) (about 4" long)
• 3.5mm male bullet connector (24)
• 3-pole bullet connector female (8) (MT-60 3.5 mm)
• Small flathead screws (#2-56 1/4" length)

Steps:

1. Cut a notch in one end of the pvc tee as shown in the photo above. Then drill a hole in the 1" end cap to match the notch in the pvc tee. Fit them together to make sure they line up.
2. Drill holes in top of the 1" end cap to match your motor mounting holes.
3. Secure the motor to the end cap using the mounting bolts that came with your motors.
4. Run the three motor wires through the hole in the end cap. If your motors did not come with wire connectors, add them (I used 3.5mm male bullet connectors).
5. Attach the pvc tee to the end of the drone arm, and run the 3 motor wires through the pvc tee. Solder wire connectors to each wire (I used a 3-pole bullet connector female - MT-60 3.5 mm).
6. Connect the three wires from the motor to the wires running through the frame. You don't need to worry about connecting them in any order. Secure them with electrical tape or shrink tubing.
7. Attach the 1" end cap and motor to the top of the pvc tee, securing with small screws.
8. Add the 4" pvc pipe to the bottom of the pvc tee to form a short leg.
9. Finish with the 3/4" end cap on the bottom of the leg.
10. Secure all joints with the small flathead screws (2 at each joint).

Note: The 1" end caps I used were slightly too large for the 3/4" tee. I used a bit of electrical tape around the tee to make sure I had a snug fit.

I found that the center ring tended to sag slightly, which is OK when the drone is flying but made it so that the battery rested on the ground when the drone landed. LiPo batteries are sensitive to damage, and can cause dangerous fires, Since I didn't want to land on the battery every time i flew the drone, I added a little support and height to the center ring.

Parts:

• 3/4" pvc pipe (4) (black) (about 4" long)
• 3/4" pvc end cap (4) (black)

Steps:

1. On the center ring, attach the short 3/4" pvc pipe to the open end of the 4-way connector.
2. Repeat for the other three legs.
3. Secure the pieces with small flathead screws.

Note: LiPO batteries can be dangerous if mishandled, overcharged, or not stored properly. Use caution. Here's a link to some safe handling information.

This is not meant to be an instructable in drone electronics. I highly suggest that you take the time to learn about the major components of UAV drones before this build, but I'll cover the basics as well as I can.

1. The power distribution board (PDB) is a printed circuit board that routes electric current from the battery to the motors and to the flight controller. I was lucky enough to find a PDB that was capable of handling the current needed and had a large hole in the center - a fortunate design for my drone. This hole fits nicely over the 5-way connector at the center of my drone.
2. Electronic speed controllers are devices that respond very quickly to signals from the flight controller, telling the motors to either speed up or slow down depending on the signal sent from the radio transmitter, or from GPS data or other data. They are rated by the number of amps they can handle, and I had some 40 am speed controllers left over from another project.
3. The flight controller is a processing unit that takes input from the radio transmitter in your hands, or input from other electronics that sense the drones position, and adjust the flight of the drone as necessary. Modern flight controllers also have a GPS/compass module, gyroscopes, altimeters, smart power units, and other features.
4. The radio receiver is a small unit that receives input from a radio transmitter, usually a hand held unit, and sends the input to the flight controller. Your receiver and transmitter need to be compatible.
5. Batteries supply the electricity needed to power the motors and any other devices (flight controller, camera gimbals, servos, lights, etc.) Because of the size of this drone, I used a large 22,000 mAh 6s battery.

I used the Naza-M v2 flight controller, because it's sophisticated enough to handle my octocopter, cheap enough to fit my budget, and it works for me right out of the box. DJI is a proprietary platform, and not really hackable (at least not by me), but there are other open source options and many instructables on how to create your own flight controller.

I secured the electronics to the drone with some 1/8" carbon fiber plates, separated by standoffs (threaded tubes). I secured the electronics using the 2-sided sticky pads (3M) and secured the battery to the bottom of the drone using zip ties. Then I was ready to fly!

My first flight was a success, and I got about 18 minutes of hover total. I didn't take this drone out of my back yard, because as I said earlier, it was just meant as a proof of concept for creating a drone frame using pvc, a relatively cheap material compared to carbon fiber.

I would never actually use this drone for anything other than a fun building experience. The fact that it flies well is great, but I know that for serious work, I'm going to want a lighter, stronger frame for extended flight times and crash resilience. What I love about pvc, though, is that any breakage due to crashes can be easily and cheaply fixed!

Let me know in the messages if I can provide any information not in this instructable.

Enjoy!

Note: The two files below are videos clips (mp4) of bench testing the motors (8,646 KB) and my first flight (21,920 KB) - yes, the landing was a bit hard.

Fun Fact: The background noise and flying insects in the First Flight video are from the 17-year cicada hatch in Maryland, summer 2021.