Abstract: A wheeled self-propelled vehicle has a load-carrying body, such as a platform or a driver's seat, which is horizontally rotatable on a spider-leg frame having a caster or support wheel swivelably mounted at the free end of each leg. The body is rigid with a vertical shaft carrying at its lower end a mounting for a guide wheel driven by a motor. Rotation of the body with reference to the frame imparts a desired orientation to the guide wheel which touches the ground, under load, with sufficient force to exert traction for advancing the vehicle. The body rests on the frame by way of one or more shock absorbers or springs which may be adjustable to different loads. The support wheels and the guide wheel may be positively interlinked, through a chain or toothed-belt drive, to rotate in unison about their respective swivel axes.