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 : the fact that the machine itself , as opposed to the operator &# 39 ; s leg , changes the leg &# 39 ; s naturally linear motion to rotary ; and a smoother , more efficient means of drive - ratio variation with the added advantage of infinite variability within limits .