Made of cardboard and radio controlled,
this model allowed engineers to test
the design. The base was made of casting
resin. If you look closely you will see that the wheels almost touch in the middle. Also, they were mounted on "Lazy Susans" and driven by a worm drive. Also, the biggest design change was moving the batteries from on top of the wheel edges to being inboard. This change is what gives Topo the advanage of pusing away from a wall when the wheels come in contact, a feature no other robot has! The arm socket is mirrored corner cube drawing (3D perspective string drawings). Very interesting effect, but expensive at the time to reproduce.
Photos courtesy of Doug Jones