Our mechanical subteam was composed of Colin Takeda, George Tighe, and Justin Yuan.
The goal of this project was to create a self-balancing unicycle in which a mass on top of a pendulum could be sustained in an unstable equilibrium. Three days prior to the end of this project, the team was forced to pivot and modify the project due to a critical sensor failure. That being said, the original intent was to create a balancing unicycle; in order to accomplish this, the team ensured that all mechanical design decisions were driven by hand calculations and simulations.
The team’s final unicycle design incorporated a frame comprised of steel square tubing that could be easily welded, an off-the-shelf wheel assembly, a 24V 250W DC motor, two 12V batteries, a steel motor mount plate, and a dumbbell for mass. The drivetrain utilized chain and sprocket, with a gear reduction ratio of 7.2:1 The frame and all mounts were welded in house. The wheel axle can be repositioned along the frame in order to tension the chain.
Once the decision was made to pivot and create a scooter, the mechanical design followed much more of a rapid prototyping process. Due to the time constraint and lack of resources, we improvised most of the scooter design through scrap parts found at Olin. We removed the rear wheel off a Razor scooter and used its front wheel plus steering column as the front portion of our final assembly. An aluminum round tube was found and welded onto the steering column to extend the height of the handlebars. Scrap MDF was used to create a deck as well as battery enclosure. A hardboard plate was used to mount electronics. Three button enclosures were 3D printed and ergonomically placed on the handlebars to provide intuitive controls. In 36 hours, the team managed to successfully convert the electric unicycle to a functional first-run prototype of an electric scooter.