How Sleeve-valve Engines Work

Sleeve Valves by Air -- Use in Airplane Engines
1940: Ground staff prepares to load a Hawker Typhoon with bombs.
1940: Ground staff prepares to load a Hawker Typhoon with bombs.
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Harry R. Ricardo (later "Sir" Harry Ricardo), born in London in 1885, didn't wait until college to begin his engineering studies. He observed and absorbed at the knee of a local machinist as a young boy, and would go home from the machinist's shop to apply his new knowledge in building engines. He would later say:

"As a child, I was always fascinated by engines and mechanical motions generally, and above all, by the great mystery as to how such things were actually made...looking back, I think I learnt more of actual value from these early and very crude attempts at design and manufacture than from anything else" [source: University of Cambridge].

Ricardo, in his working engineer adulthood, was an incurable overachiever. In addition to tweaking the engines on tanks that helped break the stalemate of World War I, he led ground-breaking research into assigning octane ratings to different grades of fuel.

Perhaps his most notable contribution in the World War II years was his work on making the sleeve-valve engine better.

Ricardo theorized in the 1920s that a sleeve-valve airplane engine could generate greater horsepower than a comparable tappet-valved engine because it could generate a higher compression ratio.

It so turned out that by 1941, British aircraft including the mainstay Supermarine Spitfire fighter plane, were taking a pounding from Germany's superior Focke-Wulf Fw 190. The Fw 190s also launched ground attack raids on Allied installations with near-impunity, since nothing could catch them at low altitude after they dropped their bombs.

The sleeve valve-engined Hawker Typhoon, entering service in 1942, changed that. Propelled by a 2,180-horsepower Napier Sabre engine, the "Tiffy's" extra get-up-and-go meant it could not only shoot down quick Luftwaffe interlopers, but it could carry bombs as well. Later in the war, bomb- and rocket-equipped Typhoons would prove pivotal in supporting Allied ground forces as they tightened the noose on the Nazis and ended the war in Europe [source: Rickard].

Despite the sleeve-valve engine's exemplary military record, the writing was on the wall: jet engines would dominate commercial and military aviation from the postwar years forward.

The legacy of Knight, Ricardo and others would not completely go away -- engine enthusiasts would memorialize the sleeve-valve engine with home-built models and on Web sites in the decades to follow. Some flying model planes use miniature sleeve-valve engines. And it's conceivable the technology could experience a resurgence in some of the world's largest and fastest-growing automotive markets.

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