An apparatus and method is disclosed for displaying a secondary layer of information in a graphical user interface where the second layer of information is revealed when a point on the circumference defined by radius \u201cr\u201d originating at the x,y coordinates of the cursor covers a point in a secondary content of the second layer. An incorrect incremental update may corrupt a navigation database. A power transmission shaft has an upper end coupled to the rotor and movable with the eccentric motion of the rotor, and a lower end constrained to rotate in a concentric manner with respect to the longitudinal axis.