Abstract: 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.