<p>An engine device ( 10 ) consumes air under pressure to produce usable mechanical power. The device includes a wheel ( 28 ) rotatably supported within a tank of fluid ( 52 ). A plurality of pockets ( 40 ) at spaced positions about a periphery of the wheel are selectively filled with gas on a rising side ( 30 ) of the wheel and evacuated of gas on the falling side ( 32 ) of the wheel such that buoyancy of gas in the pockets on the rising side of the wheel causes rotation of the wheel to produce usable power at a power take-off shaft ( 24 ) of the wheel.</p>
