A wheel assembly for a small-scale machine includes a pair of opposing, individually-driven wheels, associated motors and possibly one or more gear assemblies. The motors receive separate drive signals from a control electronics subsystem of the wheel assembly. The motors can be connected to the wheels via the gear assemblies. Because the wheels are separately driven, driving the two wheel assemblies at similar or different speeds drives the wheel assembly over straight or curved paths. An orientation assembly allows the orientation of the wheels to the machine to be controllably altered. A height adjusting assembly allows the distance between the wheels and a point on the machine where the wheel assembly is attached to be adjusted. The rotational axis that the wheel assembly rotates about when re-oriented need not pass through either wheel of the wheel assembly. The wheels can be driven by control signals generated by on-board control electronics.