The NASA Rover Challenge is an annual human-powered vehicle contest based off the design constraints of the Lunar Rover of Apollo 15-17.
- Must be human powered by one male and one female.
- Must collapse to fit in the volume of a 5 ft. cube.
- Must be propelled by non-pneuamtic (airless) wheels.
- Must be carried by two people over a distance of 20 ft.
CHASSIS DESIGN AND BUILD
The vehicle chassis and seating configuration was an adaptation of previous years' entries to the contest. We made design revisions based off ergonomic studies with low-fidelity, full-scale mockups. I was responsible for creating the final CAD dataset incorporating the team's design decisions, and creating part documentation for the CNC tube vendor. The chassis was constructed by brazing thin-walled chromoly steel tube.
I was also responsible for designing the differential driving the rover's front two wheels. The final star ratchet design was significantly lighter and more compact than the previous years' iterations. Excluding the chainring, the final volume of the system was a 2" diameter x 6" long cylinder.
The differential had to be made as lightweight and compact as possible, and assembled using only mechanical fasteners. Traditional bicycle freewheels tend to be extremely heavy, and are easily damaged if directly welded on to a drive shaft. We decided to adapt the freewheel system in the DT Swiss Star Ratchet bike hub. The design process involved drafting and fit-testing different size permutations of the individual components.