3D Printable Ornithopter

In this Instructable, I will go through the steps of building this rubber band powered ornithopter that I designed in Fusion 360. I am currently attending Rensselaer Polytechnic Institute.

• 6 skewers with a 1/8 inch diameter.

- (3X) 7 inches long

- (1X) 2 3/4 inches long

- (1X) 3 1/2 inches long

- (1X) 1 1/2 inches long

• Wire
• Paper
• Rubber bands (of varying lengths and stretchiness)
• A straw
• Spacers (small beads, a thin straw cut into segments, etc.)
• Access to a 3D printer
• Glue (hot glue or super glue should work)
• Pliers
• Scissors
• Drill with 1/16 inch drill bit

Using Fusion 360, I mocked up a modular design for an ornithopter. The reason for this being that it would allow for easy tweaking and alterations just by replacing a skewer instead of having to completely reprint the design if I needed to make an adjustment. When designing this, I was not sure what the best dimensions would be for this machine, but this design allowed me to play around with the dimensions until I got the ornithopter working. And just because I got it working, does not mean that these dimensions are ideal, so I would suggest that you play around with the length of the skewers and let me know if you find any more efficient combinations of lengths.

Once I had designed the ornithopter in Fusion 360, I went on to print out the parts (attached is a file of all the parts). Make sure to clean up the pieces and remove any unwanted supports.

Cut the skewers to length (3X 7 inches, 1X 3.5 inches, 1X 2.75 inches, and 1X 1 1/2 inches long). Now slide the skewers into the 3D printed parts as shown in the video and diagram. Using a 1/16 inch drill bit, drill through the skewers wherever there is a hole in the printed part.

We will need to bend a few different pieces of wire. There are two little pieces that attach the wings to the body and act as hinges. Then there is the driving crank that attaches at the bottom front of the body. The rubber band will be looped around this wire. And lastly we need a connecting wire that connects the crank to the wings. This last wire also acts as a hinge where the wings come together at the center. When choosing the right wire, we must consider its weight as well as its strength. I found that the crank must be made out of a stiff wire so that it does not bend under the stress of the rubber band, but for the other wires, I was able to get away with using thinner wires to keep the ornithopter as light as possible. The crank is the only wire that has dimensions. To find the length of the connecting wire, when the crank is horizontal, the wings should be flat.

For the wings, I just used regular printer paper, but I would recommend experimenting with different weight/stiffnesses of paper. Fold and cut the wings as shown in the diagram. At first I left the wings as a rectangle, but after several unsuccessful flights, I trimmed off the back corners which helped immensely. Perhaps there are even better wing shapes. Experiment! I glued them on with hot glue and in some cases super glue.

Now add the rubber band, wind it up, and give it a toss! Test out different rubber bands, maybe even putting two on at once to add extra power. Keep experimenting and tweaking the design until you're satisfied. Cheerio!