Mono: One motor. Single motor walker. This is controlled with a Miller type configuration. I made the gear motors myself from an old CD player drive motor and a toy from McDonalds (see gbmotor).

After assembling the two motor walker, one of the motors detached, due to the flailing during gait establishment.

This was a very important success for me. Seeing this guy walk, as simple as its construction is, was very motivating. He can only handle a 0.25" step, but it is enough to demonstrate the two motor - four legged walking approach for under $10. With that, on to bigger (or smaller) better walkers.