Axially rotating free piston

An axially rotating piston device, comprising:

• a housing which defines a cylinder having a length disposed between a first cylinder head and a second cylinder head;
• a shaft rotationally journaled proximate a first shaft end and second shaft end to a corresponding one of said first cylinder head and said second cylinder head, said shaft having a spline extending radially outward along the longitudinal axis of said shaft within said cylinder;
• a first piston in said cylinder, said first piston having an axial passage communicating between a first face and a second face, said axial passage having a groove radially extending outward along the longitudinal axis of said axial passage which corresponding slidably mates with said spline of said shaft allowing slidable engaged relation of said first piston along the longitudinal axis of said shaft and fixed rotational relation of said first piston about said shaft, said first piston and said pair of cylinder heads defining a first chamber and a second chamber within said cylinder;
• and
• a first channel guide and a first annular channel each correspondingly coupled to a cylinder wall or said first piston, said first annular channel having a non-circular channel path, said first channel guide slidably engaging said annular channel, whereby occurrence of sliding engagement of said first piston along the longitudinal axis of said shaft generates axial rotation of said piston in said cylinder and by fixed rotational engagement of said groove of said axial passage with said spline of said shaft generates a corresponding rotation of said shaft.