Design Process (HW)

Objective: 

The goal of our project is to replicate the motion of a bird flapping its wings, through the controlled extension and retraction of two identical wings, attached to the main body, resembling a bird. 

Our process:

We began with a basic sketch of what we wanted the bird to look like, with a main body and spine-like elements for the wings. The idea was to connect all of the wings via thin plastic (like a plastic bag) to have an accordion style fanning of the wings. In the sketch below, the spine-like wing pieces and “Ziploc” connection can be seen. Additionally, we began to think about how we wanted to replicate rotational motion, and looked at a rotating disk with a shaft that sits inside a loop that slides horizontally. As the disk rotates, the shaft is guided in a circle, which causes the translational motion of the slider. That would allow for the translational movement of the wings. 

Figure 2.1. First draft of the side view of the bird and the initial sliding rotation mechanism idea.

The downside of this initial sketch was that it did not accomplish the complexity of motion that we aimed to replicate. We wanted the wings themselves to move, not just the “shoulder” portion of the bird. This made us refocus our thoughts on how birds extend and retract their wings, which are closer to a planar four-bar mechanism. Thinking about the skeleton of a bird, we sketched a mechanism that resembled an “M” and “W” combined shape, where each vertex was a rotating pin joint, seen in Figure 2.2. This new idea allowed us to plan a more complex mechanism that we then had to determine how to control the motion bilaterally.

Figure 2.2. Second draft of bird wing design with more complex motion.

This design gave us a better understanding of how we should connect the elements together to have equivalent motion on either side. To make it slightly more complex, however, we made the two sides separate, instead of keeping them together in the middle. This posed a new challenge for how to allow the motion to stay synchronized. This sparked us to research different rotational mechanisms based on what we were taught in class. We liked the idea of slider cranks, similar to the slider crank assignment, but we quickly realized that it would cause opposite motion in each of the wings (one would be more extended, while the other would be more retracted). We shifted towards gears at this point and looked at simulated videos to see how feasible this design would be. One of the inspiring videos that we based our final design on is seen below in Figure 2.3.

Figure 2.3. Inspiration for gear design which allows for synchronization of wing motion.