Tiny SUPER 12.7cc

A Spark Ignition Two-Stroke by JC Magee

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This rear induction, spark ignition, two-stroke appeared as a three part series in Popular Science magazine of June, July, and August, 1946. It is headlined as capable of 13,000 rpm, which is modest by today's standards, but not awful for a 12cc sparkie designed for home construction from bar-stock, using nothing more than a lathe and some hand tools. For a completed example of the engine, see the Inside the Square Watzit.

The complete series plans are given below for those who would like to build one, or just enjoy examining model engine plans. Although the design simplifies crankcase construction while providing an unconventional but practical mounting scheme, the use of a blind cylinder bore and a "full" crankshaft with a split big-end connecting rod will add to the work required. The piston rings are cold-formed by placing an over-size ring on a mandrel with a clamp which holds the gap closed while the outside diameter is machined to fit the bore. This has proven to be quite an acceptable alternate to heat treating.

The plan presentation and instructions are clear and excelent. They are a tribute to the author and the magazine editor, although typical of many similar sets which appeared in PS and similar magazines immediately following World War II, when the level of skill was higher in the population due to the requirements of a war economy, and the trade, or "shop" classes run by schools until the early 1960's. Somehow, such classes are now deemed too dangerous for today's youth—and of little interest to them in any case. That's progress... *sigh*