Design of a Two-Stroke Cycle Spark Ignition Engine Employing a Scotch-Yoke Crankshaft Mechanism

This paper discusses the design aspects of a two-stroke cycle, spark ignition engine intended for light aircraft propulsion. A modified form of scotch-yoke crank mechanism is employed, and by utilization of two such reciprocating assemblies set at 90 degress to each other, a compact 4-cylinder radial engine configuration results. The unique mechanical design considerations of the scotch-yoke combined with the two-stroke engine cycle are examined in detail. The design offers an inherently balanced, low vibration machine employing a full circulatory lubrication system while retaining basic two-stroke engine simplicity. A prototype has been constructed which meets all initial design criteria and test results are presented.