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Abstract

The object of this study was to apply the technique of synthesis to the design of a small power saw. The study produced experimental data on optimum chain speeds, engine vibrations, noise levels, and heat transfer coefficients for reciprocating cylinder heads, and led to a simple free-piston configuration in which a piston oscillated between a mixture of air and fuel in one end of a closed cylinder and a spring in the other. The feasibility of developing the configuration into a practical reciprocating engine was verified by designing, building and testing a prototype. The prototype incorporated such novel features as instant, effortless starting and stopping, automatic throttling, self-cooling, compression ignition of a carbureted air-fuel mixture, and a balanced engine. Uncontrolled ignition timing reduced engine efficiency, and the lack of inertia made engine stalling easy and carburetor adjustment difficult. The computed results suggest that a developed 3 lb free-piston power saw will produce 1.0 hp at 6,400 cpm and have a specific fuel consumption of .9 lb/shp-hr.