String Bike

"The STRINGBIKE® has two identical but oppositely directed driving units at either side of the frame. The rotation of the pedals forces a swinging arm to swing forward and backward around its shaft. The forward segment of this motion pulls a rope wound around a drum on the rear shaft that makes the wheel to rotate. As the two sides move in mirror symmetry, there is always one arm that moves forward, thus the rear wheel is always driven. In this way the task of actual driving is taken unnoticeably from the right to the left side and vice versa." www.stringbike.com for puppets.