The design process took many iterations. The first design we came up with was a series of offset 4-bar linkages that rotated at a single input, as seen in the figure below. There were 4 independent leg-walking mechanisms, driven by a single input. With multiple leg mechanisms, this ensured that at least one mechanism would be in contact with the ground at all times and thus ensured a steady movement.
Multi-legged mechanism design
However, this design was not without it's drawbacks. The main problem with the above mechanism is that the legs have to cross over a shared shaft, which is impossible in practice. This can be remedied by spacing the leg mechanisms out, by either placing them in opposite sides of a main body or arranging them in specific manners such as a quadruped animal. However, this goes against the idea of simplicity we want, as it would mean multiple input shafts and points of failure.
Thus, we decided to simplify the mechanism above even further, sticking with only one leg so that there was no interference between parts. To ensure steady motion and prevent rocking, we decided to implement two legs in phase with each other, each at one side of the prototype.
Single leg mechanism
With the above in mind, we designed the prototype in SolidWorks. We started by modeling the leg mechanism as a set of four simple links, with holes for shafts or bearings to allow for movement. Once that was designed, we designed the main body of the prototype to accommodate two legs, one on each side. We aimed for the simplest design possible to reduce manufacturing time. Finally, to balance the prototype, we designed a triple-wheel system that the prototype rests on. The wheel supports are designed long enough that the end point on each leg is able to contact the ground without too much pushing. The final design is shown below.
