EXPANDABLE AND RETRACTABLE WHEEL ASSEMBLY

An expandable and retractable wheel assembly in accordance with one or more embodiments includes a hub structure having a circular periphery and a rim expandable in circumference from a retracted circular position to one or more expanded circular positions. The rim engages and is supported by the circular periphery of the hub structure when in the retracted position. A plurality of linear actuators is attached to and supported by the hub structure. Each linear actuator includes a piston rod and a drive system for moving the piston rod from a retracted position to one or more extended positions, wherein a distal end of the piston rod engages and moves the rim when the piston rod is extended and also supports the rim in the one or more expanded rim positions.