Methods and apparatuses are disclosed that rotate a first member about a
first point relative to a chassis, wherein the first member is rotatably
coupled to a second member at a second point. A second member is
counter-rotated at a ratio of the rotational speed of the first member
wherein the second member is rotatably coupled to the third member at a
third point. The third point is translated in response to the
counter-rotating second member in oscillatory motion along a path. The
third member is pivoted at a third point and fluid is moved in response
to the motion of the third member. A force is applied to the chassis due
to the interaction of the third member and the fluid.