Objective
I wanted to show appreciation for my Lithuanian teacher and tutor, who had helped me master my mother tongue. I decided to 3D print a model of Gedimino Pilis, a famous national landmark in Lithuania. Inside, I created a secret compartment, which opened with a gear system. The compartment contained a thank-you note.
Mechanism Design
I used Fusion 360 to design every component in the system. The main components were the shell (the castle exterior itself), the internal compartment (with a gear rack along the side), the gears themselves, and a locking mechanism (to stop the compartment from drifting out).
Engineering Challenges
- Getting 3D printed plastic gears to mesh properly (and spin without locking up) was a huge challenge. I had to print several iterations, increasing the leeway between teeth each time. Even after that, I had to sand the gears down so they would not lock up instantly. The final product still required lots of force to turn, but I was happy with the results. It took me less than 2 weeks to go from learning about gears in Fusion 360 to having a working prototype.
- The locking mechanism became unnecessary, as the internal compartment had too much friction to slide out on its own. However, I still made it work: I used the spring from a ballpoint pen to force a small peg into the gear rack. You had to pull on a small tab to unlock the rack. However, this made it hard to open the compartment initially: you had to pull the tab while carefully spinning the handle to turn the gears.
