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Two-stroke engine cylinders have ports to exchange gas. While the engine runs, the piston and its piston rings slide over these ports in the cylinder walls, and the rings may project into the ports. This paper explores this, first, by reporting a simple model of material mechanics that predicts rings might project into ports, and second, our experimental verification. We installed strain gauges on the bottom of the top and second rings, over the intake and exhaust ports, and ran signal wires out of the engine. We then examined the variations of strain while running the engine. Our analysis confirmed how the dimensions and the tension of the rings, and the dimensions of the ports, affect ring projection into ports as static displacements.

In most air-cooled engines, aluminum cylinder blocks are lined with cast iron, which enjoys a higher wear resistance than aluminum. Recently, rather than a turned periphery, an increasing number of cast iron liners have employed as-cast periphery with projections, so the liner better adheres to the aluminum cylinder block, and improves heat transfer. This study attempts to maximize heat transfer while minimizing cylinder weight, by comparing four liners: (1) a cast iron liner with higher projections on its periphery, (2) a cast iron liner with lower projections, (3) a cast iron liner with lower projections, and aluminum-silicon coated on its periphery by thermal spraying, and (4) a high-silicon aluminum alloy liner with aluminum-silicon coated by thermal spraying. These four experimental liners were fitted in a die-cast low-silicon aluminum-alloy cylinder block, to investigate their joint and cooling characteristics.