Abstract: A crank mechanism for bicycles, in particular racing bicycles on roads, unpaved roads or tracks, includes a winch rod, pedaling members coupled with an end of the rod, and an arm of a connecting rod, of which one end is rotatably coupled with respect to the rod in correspondence of the end of the rod. The pedaling means are rigidly fixed to an opposite end of said arm.

Abstract: The unit comprises two variable-length pedal cranks (20) having a common rotation pin (21) of transverse axis (A), and a mechanism (34, 35, 36) for varying the length of the two pedal cranks (20) on the basis of their angular position; the position of the axes of the pedals (25) in the vertical plane of projection defines, as the angular position of the pedal cranks (20) varies, an endless closed curve (F) about a reference axis (R) which is displaced by an angle of about 15 degrees forwards from the axis (N) passing through the center of the seat (11) of the bicycle and intersecting the axis (A) of the pin (21).

Abstract: The unit comprises two variable-length pedal cranks (20) having a common rotation pin (21) of transverse axis (A), and means (34, 35, 36) for varying the length of the two pedal cranks (20) on the basis of their angular position; the position of the axes of the pedals (25) in the vertical plane of projection defines, as the angular position of the pedal cranks (20) varies, an endless closed curve (F) about a reference axis (R) which is displaced by an angle of about 15 degrees forwards from the axis (N) passing through the center of the seat (12) of the bicycle and intersecting the axis (A) of the pin (21).