Two Saxon inventors developed a drive unit for bikes, which is characterised by a 4 pieces assembly group that replaces the foot pedal and treadle of a conventional bike. The cyclist can sit or stand and uses all his body weight to perform with big or little step sequences a max. hinge moment. This leads in a min. physical strain for joints and leg muscles and thus its suitable for untrained people with health problems, e.g. joint or urological problems. All kinds of cooperation are welcome.