Abstract: A gravity rotary device including a first disk having a central axis; a peripheral axis of rotation arranged at a distance from and parallel to the central axis; a peripheral rotary shaft suitable for turning about the peripheral axis of rotation; and a mass support mounted on the peripheral rotary shaft and having a mass suitable for being moved away from the rotary shaft in order to produce torque causing the rotary shaft and the first disk to pivot. The device also includes a reduction gearing arranged between the peripheral rotary shaft and the first disk; a means for fastening at least a portion of the reduction gearing in a stationary position in order to prevent it from turning about the peripheral axis of rotation; a freewheel arranged on the peripheral rotary shaft; and means for modifying the angle of inclination of a mass support on the peripheral rotary shaft.