proximal exit point 25 u2032 and an opposite distal exit point 25 u2033 on the wheel assembly 100 as seen in fig1 each of the spring biased hinged flaps 30 is placed over an air chamber or air bag 35 suitable for holding a quantity of compressed air at the outer edge of each flap 30 are mounted the ball bearing flap wheels 40 turning now to fig3 through 5 another apparatus constructed and operating in accordance with the present invention is shown at 300 and is seen to include a rotary member 310 mounted on an axle 312 for rotation about a axis of rotation 313 while immersed in a liquid preferably in the form of water 314 rotary member 310 has a perimeter 316 spaced radially from the axle 312 and from the axis of rotation 313 a plurality of chambers are shown in the form of collapsible gas bags and are illustrated as air bags 320 spaced circumferentially from one another along the perimeter 316 of the rotary member 310 axle 312 is oriented in a substantially horizontal orientation so that rotation of the rotary member 310 about the axle 312 moves the air bags 320 between an uppermost elevation 322 and a lowermost elevation 324 each air bag 320 is located relative to a counterpart air bag 320 such that upon an.