It looks like one of those linear drive systems have shown their face again. It was in 1897 that a patent, granted to a teen Swedish inventor Birgin Ljungström, showed the world a linear drive bicycle where the pedals moves in linear, reciprocating fashion. The project was sponsored by dynamite inventor Alfred Nobel. Ofcourse, numerous other linear drive systems for bicycles have been invented since then.
Recently shown on the Internet by a Hungarian bicycle design team was a linear drive bicycle. The system we're looking does involve circular pedal motion but the symmetric cam mechanism ensures that a string or rope constantly winds and unwinds on both sides of the bike, transmitting torque through the freewheel of the rear hub. Some videos are attached below to show the design and operation of the drive.
Discuss the possibilities and negative aspects offered by a symmetric drive system such as number of extra moving parts, ease or difficulty of adjustment, gear ratio variability, safety etc.