Abstract: An exercise machine has a first frame member, a second frame member that is movable with respect to the first frame member, and a locking device having at least one cam that is rotatable into and between a locked position in which the cam abuttingly engages and thereby retains the second frame member in position with respect to the first frame member and an unlocked position in which the cam is spaced from and thereby frees the second frame member for movement with respect to the first frame member. The cam has an engagement surface with a contour that follows a logarithmic spiral curve defined by the following parametric equations: x(t)=r(t)cos(t)=aebt cos(t), and y(t)=r(t)sin(t)=aebt sin(t), wherein e is the base of natural logarithms and a and b are arbitrary positive real constants.

Abstract: A bicycle having a pair of wheels and a frame formed of two crossing bars that are detachable from each other so as to form a separate unicycle and a pedal bike, one of which includes a handle bar at a top, and the other a seat at its top, while each has one wheel at a lower end.