Abstract: The apparatus includes a steeped axially displaceable piston in a stepped cylinder housing, and a rotary shaft is axial fixed relative to the housing and extends into the piston reduced diameter end portion. The piston reduced diameter portion and the housing having a cooperating set of first teeth while the piston and shaft have a cooperating set of second teeth whereby at least one set of the teeth serve to convert axial movement of the piston into rotary motion of the shaft. The shaft is supported in the housing adjacent where it exits from the housing by a first bearing while a second bearing is provide radial adjacent to the juncture of the housing enlarged and reduced diameter portions that supports the interior end portion of the shaft in the piston reduced diameter portion. A third radial bearing is provided between the enlarged diametric portion and the piston enlarged diametric portion in axial remote relationship to the first bearing.