CalSMV Electric Vehicle Powertrain

CalSMV is a competition club at U.C. Berkeley that strives to build the most efficient electric vehicles. I joined the club in Fall 2019 as a member of the powertrain team, helping with the final details of the club's nearly finished vehicle. In Fall 2020, the club began developing a brand new vehicle, and I was selected to lead 8 other team members in designing the vehicle's powertrain unit.

The powertrain unit is built upon a welded tube subframe which mounts to the vehicle's primary chassis, allowing for easy assembly, testing, installation, and interchangeability. We chose to maintain the same one-wheel drive system used in our previous vehicle for simplicity and efficiency.

The drivetrain consists of a precision ground aluminum drive-shaft secured to the subframe with two taper bearings. The driven wheel hub is secured to the driveshaft with a keyway and castle nut, and features mounting surfaces for both the rim and brake rotor. A 60-tooth sprocket is mounted to the inner side of the drive-shaft for alignment with the motor and provides the required gear reduction. For this new vehicle, we decided to switch from a belt drive to a chain driven system.

The free spinning wheel hub uses two taper bearings mounted to a fixed spindle, also secured with a castle nut. A 5-lug bolt pattern will be installed into the wheel hub end plates to accommodate the vehicle's rims.

This work was completed during Fall 2020 and we are continuing to improve the design during Spring 2021. Our goals for this new semester include adding reinforcement plates throughout the subframe, optimizing the machined components for weight savings, designing a custom 1kwh battery, developing a steering system, and experimenting with a two-stage chain drive system.

Here is a screenshot of our club members during one of our Zoom meetings.