This is a dual acting compressed air engine than was built based on plans published in Live Steam Magazine. My version is made from cherry, walnut, maple and red heart woods. It is finished with paste wax on areas where moving parts mate and antique tung oil everywhere else. There is no metal whatsoever in this engine. All components are held together with walnut #2 tapered pins. The engine runs very nicely on 5 pounds of air or so.