Katrina Lee & Emma Liu’s BIRD!! | ENGI 210: Prototyping and Fabrication

Hi! This is Katrina Lee and Emma Liu, and we are excited to walk you through the process of creating our mechanical bird! This project was our first time working with mechanical elements, and we truly enjoyed the learning process of problem-solving and designing.

Gate 1: Idea Generation, Sketches, and Drawings

To start, we explored the 507 Mechanical Movements website, identifying a few mechanisms that interested us. After discussion and browsing Pinterest for inspiration, we decided to incorporate cams into our midterm project. Ultimately, our design was most similar to movement 96 (heart cam). Our model uses two circular cams of different sizes attached to a dowel, allowing the bird’s wings to move up and down. We opted for a circular cam instead of a heart-shaped one to ensure smooth functionality.
We then sketched multiple ideas for the wing movement. Initially, we considered a crenelated bar mechanism, but it was overly complex and unreliable.
To refine our concept, we created a 3D model in Rhino, which helped us visualize component attachments and spacing. Rhino allowed us to make precise adjustments, considering material thickness and dowel dimensions. The materials we used were:
Wood thickness: 1/5 inch
Dowel diameter: 3/8 inch

Below is a screenshot of our 3D Rhino file and an axonometric drawing illustrating our mechanism.

Gate 2: Low-Fidelity Prototype

Once our digital files were ready, we laser-cut a low-fidelity prototype using cardboard to test our idea. This step ensured all parts fit together properly and allowed us to experiment with the bird’s wing living hinge mechanism. However, when cutting the wing, the hinge pattern was too dense, causing the cardboard to catch fire. We quickly stopped the machine and extinguished the fire by smothering it with a weight.
During assembly, we noticed that the original bird placement was too high and had to make some adjustments. The cam mechanism functioned but had friction issues due to the cardboard’s corrugated texture. We used masking tape to reduce friction. Additionally, the bar controlling the bird’s movement was not perfectly vertical, causing occasional jams. To fix this, we added a guiding wooden piece with holes to ensure vertical motion.

Gate 3: Mostly Functioning High-Fidelity Prototype

Using insights from our low-fidelity model, we proceeded to laser-cut plywood for the final version. We tested three variations of the bird’s wing, each with different living hinge densities, and chose the most flexible one. Additionally, we rastered a curve onto the cams for precise alignment, ensuring synchronized movement.
For assembly, we used finger joint techniques from a previous box-making assignment to construct the base. Sanding and hammering helped achieve a perfect fit, and modeling in Rhino significantly made the assembly process easier with the precise measurements.
However, after assembling, we encountered some issues. The cams had too much friction, making movement difficult, so we sanded them evenly with fine-grit sandpaper. The bars attached to the bird were too light to fall naturally, so we added washers to increase their weight.
Next, we worked on the sky elements by sanding and spray-painting them light blue. We applied four coats of paint, waiting 20 minutes between layers to ensure even coverage.
For final assembly, we inserted the dowel through the first layer’s holes, securing it with stoppers. Using clamps to structure the base, we ensured that all feet were straight for stability. Once secured, we attached the spray-painted waves onto the feet. After assembling the base, we used a hand saw to trim excess dowel length and sanded it for a clean finish.

Post-Processing & Finishing Touches
For a polished look, we disassembled and spray-painted each element. We started with a white primer, followed by a light blue base with a darker blue gradient for depth. To enhance the sky effect, we created cloud decals in Adobe Illustrator and used a vinyl cutter to make white stickers for the backboard. Finally, we reassembled all the components to complete our final product.