For my mid-term project, I chose to make a pendulum with escapement. Basically, by attaching a weight to the system, the gear will turn itself and make the pendulum click and swing at an even pace.

The basic process I underwent: modify the existing adobe illustrator file; laser cut the parts; test assemble the parts together; then go back to the first step and modify the AI file. By the first iteration of this process, I made my medium fidelity prototype, using which I figured out the designs that worked and those features that could be improved. This is what it looks like, very crude version of the final product and the main issue was identified immediately: the escapement.

Then the most iteration process was focused on making the gear work. It is very difficult to use the original file on the book because all the dimensions were roughly eyeballed and the way gear works was not explicitly pointed out. I ended up making tons of gears and the ratchet arms, and I even tried to adapt the file online. I made a lot test runs with the old medium fidelity prototype as the test bed.

After some test runs, I felt confident about one set of gears and assembled the whole thing together to see how it will actually work. However it failed miserably, unlike the un-turning gear in medium fidelity one, the arms clicking the gear was now too far apart that the gear would turn without really pushing the arms sideways. After this test run, I finally figured out the core to this design. The arms are pushed by teeth as gear turns. So a good design is to let one arm touch one tooth at a time. Also, as one arm gets pushed away the other arm should come down and contact the tooth on the other side. So the height of each arm and distance between them became the main focus.There were also some designs in making the tip of the arm curved so that the tooth will slide more easily as it pushes the arm.And I made at least 20 different arms before I finally got the right one. Here are some failed parts.

Now, I finally got the gear clicking! And I clear coated the parts and assembled it back together. Some notes on clear coating: I think the coating increased the weight on pendulum and actually decreased the swing radius; it also made the joints less smooth so that I had to apply some oil in order to make it run normally again; I think it also made the clicking noise quieter which is a real bummer. But still, I am glad it all worked out in the end. I really enjoyed the process of making something that actually works.

And here is a video of it in action!!