Gast rotary vane airmotors use compressed air to produce rotational motion of a shaft. Rotary vane air motors have axial vanesfitted into a slotted rotor, which mounts eccentric with the bore of themotorâs housing. The vanes extend to seal against the housing bore usingsprings, cam action, or air pressure, depending on the motor design. Torquedevelops from the pressure of the compressed air acting on one side of thevanes causing the rotor to spin.