How to Build a Rubber Band-Powered Ornithopter

Introduction

In this project, we’ll construct a rubber band-powered ornithopter—a flying device that flaps its wings like a bird. The design is based on a modular system using skewers, wires, paper, and 3D-printed parts. This project combines engineering, aerodynamics, and creativity, making it a fun and educational hands-on experience.

I created the design using Fusion 360 and chose a modular approach so that you can easily swap out parts and make adjustments to optimize flight performance. This guide will walk you through everything you need to build and optimize your ornithopter.

I’m currently studying at Polytechnic Institute, where this project originated as a fun challenge in designing lightweight, efficient flying machines.

Supplies You Will Need

Materials:

1. Skewers (1/8" diameter):
2. (3 pieces) 7 inches long
3. (1 piece) 3.5 inches long
4. (1 piece) 2.75 inches long
5. (1 piece) 1.5 inches long
6. Wire: A mix of thin wire for hinges and a stiffer wire for the crank mechanism.
7. Paper: Regular printer paper for the wings (you can experiment with other types later).
8. Rubber Bands: Various lengths and strengths to test flight performance.
9. Straw: Used to create spacers.
10. Spacers: Small beads or segments of a straw to reduce friction.
11. Glue: Hot glue or super glue works best for quick drying and strong bonds.

Tools:

1. Scissors
2. Pliers
3. Drill with a 1/16-inch bit (for precise holes)
4. Access to a 3D printer (to print the modular parts)
5. Fusion 360 or any CAD software (optional for design modifications)

Step 1: Designing & 3D Printing the Parts

Design Overview:

I used Fusion 360 to create a modular set of parts that allows easy adjustments. By using skewers for the frame and 3D-printed parts for connectors, you can swap out components without needing to reprint everything if adjustments are necessary.

Printing Instructions:

1. Download the provided STL file (attached at the end of this guide).
2. Print the parts using a standard 3D printer. PLA or ABS filament works well.
3. Once printed, carefully clean up any support material using pliers or a knife.

Step 2: Preparing the Skewers & Frame Assembly

Cutting the Skewers:

1. Cut skewers to the specified lengths:
2. (3x) 7-inch pieces for the main body and wing supports.
3. (1x) 3.5-inch piece for the central support.
4. (1x) 2.75-inch piece for the tail section.
5. (1x) 1.5-inch piece for the front nose piece.
6. Inserting Skewers into the 3D Parts:
7. Slide the cut skewers into the printed parts according to the diagram (attached or refer to the video if available).
8. Ensure a snug fit, but avoid forcing the skewers in to prevent breaking the printed parts.
9. Drilling Holes:
10. Using a 1/16-inch drill bit, carefully drill holes through the skewers wherever there are pre-made holes in the 3D parts. This ensures all parts are aligned.
11. Secure the skewers in place with a small dab of glue if necessary.

Step 3: Bending and Shaping the Wires

Making the Wire Components:

1. Wing Hinges:
2. Cut two small pieces of thin wire. Bend them into an "L" shape to serve as hinges that attach the wings to the main body.
3. Crank Mechanism:
4. Use a stiffer wire to create a crank that attaches to the front of the ornithopter. This crank will hold the rubber band that powers the wings.
5. Ensure that the crank is sturdy enough to handle the tension without bending during winding.
6. Connecting Wire:
7. Create a longer piece of wire to connect the crank to the wings. This wire will also act as a hinge point for the wings to flap.
8. When the crank is horizontal, ensure that the wings lie flat for optimal flapping motion.

Tips:

1. Test the flexibility of the wires before final assembly. The crank wire needs to be strong, while the hinge wires should be lightweight.

Step 4: Creating the Wings

Cutting the Wings:

1. Start with a rectangular piece of regular printer paper (8.5” x 11”).
2. Cut two wing shapes from the paper. The initial design can be rectangular, but feel free to trim the corners to a rounded or tapered shape for better aerodynamics.
3. Folding the Wings:
4. Fold a small edge along the front of each wing (about 1/4 inch) to create a leading edge. This improves airflow and lift.
5. Attaching the Wings:
6. Using hot glue or super glue, attach the wings to the skewers. Ensure that both wings are symmetrical for balanced flight.
7. Adjust the wing angles slightly upward for better lift.

Step 5: Final Assembly and Rubber Band Setup

1. Attach the Rubber Band:
2. Loop one end of the rubber band around the crank and secure the other end to the back of the ornithopter.
3. Ensure the rubber band is taut but not overstretched.
4. Connecting the Crank to the Wings:
5. Attach the connecting wire from the crank to the wing hinges.
6. Adjust the wire length so that when the crank is wound up, the wings flap smoothly without resistance.

Step 6: Test Flights & Adjustments

1. Initial Launch:
2. Wind up the rubber band by rotating the crank several times.
3. Hold the ornithopter horizontally and release it gently into the air.
4. Troubleshooting:
5. If it dives too quickly, adjust the wing angles upward slightly.
6. If it doesn’t gain enough height, try a longer or stronger rubber band.
7. Experiment with trimming the wings or using lighter paper for better flight performance.
8. Optimizing Flight:
9. Try different wing shapes (triangular, elliptical, etc.) to see which provides better lift.
10. Test using different rubber bands to find the right balance between power and endurance.

Conclusion & Next Steps

Congratulations on building your own ornithopter! This project is perfect for exploring the principles of flight and aerodynamics. Keep experimenting with different materials and configurations to achieve longer flight times.

If you find any improvements or optimizations, please share them—I’d love to see how others can enhance this design!