Vertical Twins

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Sir,
In your interview with Grp. Capt. Wynne you mention the “odd noises” made by his 1913 2-cylinder Swift due to “both pistons rising together”.

No wonder, because if both pistons rose together then the Swift suffered from a broken crankshaft. I know the Swift had a 180 deg. arrangement because I can remember the unusual exhaust beat of one owned by a friend of mine in 1914!

As far as I know, twin cylinder four-strokes with a 360 crankshaft arrangement were a much later development than the 1913 Swift.

Co. Mayo, Eire. Anto Brett.
[I regret the error, but the question of when 360 deg. four-stroke twins first appeared, is open—I quote from an edition of Iliffe’s “The Light Car Handbook,” published, as far as can be ascertained, in 1914-15: “The Vertical Twin-cylinder. This engine has been constructed with one piston rising when the other falls and also with both pistons rising and falling together. The twin vertical engine is inferior on all counts, except cheapness and simplicity, to the vertical four-cylinder. Its noise is less continuous, and is heard in staccato barks at low speeds. If the pistons move together, the sound of the exhaust is divided into regular intervals, but the simultaneous movements of the two pistons in one direction cannot be perfectly balanced, and there must be a certain amount of engine vibration, likely to be specially marked at certain speeds. If, on the other hand, one piston sinks while the other rises, the piston movements will balance approximately, but the sounds of the explosions will occur unevenly.”—Ed.]

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