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As a recent drone or Unmanned Aerial Vehicle (UAV) enthusiast, I started by learning to fly a small toy hobby drone, to which I then successfully designed and printed a frame for one on my Mark Two 3D printer by MarkForged. Having mastered a small drone, I decided to upscale and subsequently purchased a Cheerson CX-20 drone, a much larger UAV.

The Cheerson CX-20, like many of the popular consumer drones, is easy to fly. It has GPS and incorporates common functions like return to home and the flying of programmed missions. It is also designed to be used for aerial photography.


What is often ignored, however, is that it is equally easy to crash, and will most probably break. The body is a thin-shelled injection molded plastic that has very little impact resistance. Almost immediately upon flying it I managed to break one of the landing gear; so, I quickly 3D printed some stronger legs to replace the brittle ones that came with the drone, as can be seen in Figure 1.

Carbon Fiber Printed UAV 1

Figure 1.


While this strengthened the legs, it did nothing for the remainder of the body — and due solely to my inexperience, I had numerous crashes that necessitated the replacement of the body several times. The body of the unit is strong enough to handle the normal stresses of flying, but as I mentioned earlier, it has almost no impact resistance. Figure 2 shows the results of one of these crashes. After replacing the body several times, I decided to design my own frame that would be stronger and better able to handle impacts, and printed them on my Mark Two 3D printer.

Figure 2.

Figure 2.


Design Solutions

My main goal was to design a body that would be strong and impact resistant, with lightness being a secondary consideration. The body and its pieces had to fit on the build plate of the Mark Two, and more importantly, take advantage of the characteristics that give Mark Two 3D-printed parts their strength; most notably the use of thin plate construction strengthened by fiber. My initial design is shown in Figure 3 below.

Figure 3.

Figure 3.


The parts on the left make up the airframe section, while the parts to the right make up the landing gear. Most of parts are thin plate construction with carbon fiber used though out. (The landing gear and top bow incorporate Kevlar.) The individual parts are mechanically fastened together with 3mm screws and all nuts secured using Locktite.

One advantage of the design is that if a part does happen to break, it alone can be easily replaced, rather than needing to replace the entire body. The airframe and landing gear sections are spring loaded together for shock resistance. The battery sits between the two and the camera is hung underneath.

Testing and Tweaking

Initial testing of the frame mainly involved throwing it up in the air as high as possible (without the electronics on it, of course), and letting it crash back to the ground. I was happy to see it survive all such tests.

The completed UAV with a Mobius camera mounted on a 2-axis stabilized gimbal is shown below in Figure 4.

Figure 4.

Figure 4.


The initial flights were promising but showed a particularly annoying problem; the inability to hover and hold position in the air automatically. After a little bit of head scratching and searching the web I discovered the problem had to do with the placement of the compass. I then designed and printed  a compass mast to hold the compass and position it behind and above the rest of the electronics to avoid any electrical interference. At the same time, I also decided to relocate the GPS unit towards the front of the airframe to hopefully enable it to pick up more satellites. Fortunately, these changes in the design were easily and quickly accomplished due to the ease of making the parts on the Mark One. Subsequent flights demonstrated a much improved hover ability.

While the size of the build volume of the 3D printer caused the design to be made up of a number of individual parts, this is actually an advantage as it allows design changes to be easily accommodated. I found the tips of the 9” propellers were dangerously close to some of the wiring and any crash that would cause the drone to flip over could bend the propellers so their tips could cause problems. Fortunately, the arms are easily removable. I subsequently redesigned the arms to make them longer although I chose to print them using Kevlar, rather than carbon fiber. I believe the Kevlar will make them stiff enough for normal flying, but its resilience should help absorb and dissipate any shocks from impacts. Most importantly, I’m hoping their flexibility will absorb any motor vibrations, preventing the vibrations from affecting the video.

In addition, the electronic speed controller (ESC) pcbs previously were screwed to bosses on the arms, and I found that these bosses could snap off the arm if the arm flexed enough. The latest version has the ESC located on a floating holder to mitigate any damage to them.

My current UAV minus the camera module is shown below.

Figure 5.

Figure 5.



I am quite pleased with the result. It is an excellent example of taking advantage of the strengths of a technology in a design and working with these strengths rather than against them. I have had some minor mishaps with the drone and it has come through unscathed. I am confident my days of breaking my drone are over; so, I can concentrate on learning not to crash it, rather than putting it back together after a crash.

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