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The Nakajima Homare
(誉, "praise" or, more usually, "honour") was an air-cooled twin-row 18 cylinder radial Japanese
aircraft engine manufactured during World War II
.Producing almost 2,000 horsepower, it was used widely by both the Imperial Japanese Army
and the Imperial Japanese Navy
. "Homare" was the navy service designation, and their experimental designation for it was NK9; the army called it the Ha-45 (ハ45) or, in service, the Nakajima Army Type 4 1,900 hp Air-Cooled Radial
. The manufacturer's designation was BA (or NBA).
Design and development
Development of the Homare started in 1940, and certification was completed in 1941. It succeeded Nakajima's previous 14 cylinder Sakae
(Ha-25) engine, with its forward nine cylinders staggered from the rear nine for efficient cooling.
The design was exceptionally compact, with an external diameter of 118 cm, a mere 3 cm larger than the Sakae. With a bore and stroke of 130 mm x 150 mm, it was classified as a short-stroke engine. It was designed to output around 1800 hp (1340 kW), or 100 hp (75 kW)per cylinder. However, the tight design of the engine made it difficult to maintain quality in manufacturing, and unreliability in the field was a... Read More