Abstract: This invention replaces the crank-and-chain drive system of the conventional bicycle. A flexible drive line is pulled directly away from the hip by a stirrup located at the “ball” of the foot and drives the rear-wheel hub by means of a cone-shaped spool with a spiral groove. Routing pulleys mounted to a sliding shifter provide drive-ratio variability by adding line to or removing line from the spools, thus utilizing spool segments of varying diameter. A tensioned rewind system enables each spool, when driving the hub, to rewind the other. Benefits of this system as compared to prior art include: (1) the fact that the machine itself, as opposed to the operator's leg, changes the leg's naturally linear motion to rotary; and (2) a smoother, more efficient means of drive-ratio variation with the added advantage of infinite variability within limits.