6. Final Prototype Design

Our final design was intended to ensure stability and simplicity. We used three wheels, two in the back and one in the front, to suspend the base platform for the entire mechanism in between the stepping motions. The movement input would come from the two four-bar leg mechanisms in the back that would rotate in phase with each other to propel the entire mechanism forward. For this propulsion, the feet at the bottom of the legs would have a stepping motion, and the two legs would pick the back wheel up off of the ground at the beginning of the step and place it back down at the end. While we initially envisioned that there would be some out-of-phase leg rotation for this project, we decided that keeping the two legs in phase would be ideal to ensure that the mechanism would stay balanced and working consistently. If the legs rotated 180 degrees out of phase with each other, the mechanism would rock back and forth, potentially creating the need for a suspension system or another solution to mitigate the balance issues, so we decided to keep it as simple as possible in order to avoid this problem.

All custom structural parts were created out of wood with the laser cutter, with the exception of the gears, which were also laser cut but made of acrylic in order to ensure smooth gear tooth faces. Within the leg mechanism, steel shafts were used to connect the joints, and ball bearings were installed by hand in order to create smooth motion. The steel shafts were filed down until they fit tightly into the holes within the wooden links and the bearings. The weight of the mechanism ensured proper contact between the shafts and bearings, and for shafts that weren't connected tightly enough into their wooden holes, we used super glue to strengthen the connection. For the legs that suspended the base of the mechanism, we laser cut slits into the base for the legs to fit into, and used super glue to strengthen those connections as well. The wheels on the ground where connected to shafts that ran through bearings at the bottom of the wheel legs.

Mechanism Movement Video.mp4