Anyone looking for chainrings on this bicycle will search in vain. This early experiment in alternative propulsion by the Korean Marn T. Seol is remarkably ingenious. You pedaled up and down instead of in circles and that was exactly the problem: the designer assumed a constant speed of movement of the pedals.

When pedaling with a conventional crank, there is a rotational movement, with a deceleration and an acceleration phase in each rotation. With the Alenax you had to pedal at full speed directly from the stop at the top with every stroke, and then stop just as suddenly at the bottom. But how do you shift gears?! Well just… with your shifters. These move a cam on a lever, which makes you pedal harder or lighter.

The manufacturer must have been strongly convinced of the advantages of this type of propulsion, given the many different models that have been produced over the years. But looking at user experiences leads to the conclusion that the thing is as good as unrideable.