|
The Nakajima Ha5 is an air-cooled aircraft engine built by the Japanese Nakajima Aircraft Company. The engine was a development of earlier Japanese engines which combined features of the Bristol Jupiter and Pratt & Whitney R-1340 Wasp designs, but was expanded into a larger, two-row, 14-cylinder engine in the Ha-5. First introduced in a 1,000 PS prototype in 1933, about 7,000 civilian and 5,500 military Ha5's were built during World War II. The Ha5 had separate camdiscs for the front and rear rows of cylinders like American designs, rather than using a single, front-mounted camdisc and long pushrods to operate both rows of cylinder valves. ==Design and development== In 1917, Chikuhei Nakajima set up the "Airplane Institute" at Ojima Town in Gunma Prefecture. In 1918 they built their first airplane; the "Nakajima Type 1" with a U.S.A. made engine.〔Engine development at Nakajima 1923 - 1945〕 In 1920 the company sent Kimihei Nakajima to France to study European advances, and in 1922 started their own engine factory in Tokyo. This led to production of engines based on the Lawrence A-3 two-cylinder air-cooled horizontally opposed engine. At the time the Lawrence was an oddity. Most air-cooled engines at that time were using cylinders that rotated together with the propeller, but Kimihei overheard that an engine with good cooling capability with fixed cylinders was being developed in England. He observed the English Gloster Gamecock fighter with its Bristol Jupiter engine, which was an advanced design for the era with an automatic adjustment device for tappet clearance, spiral piping for even intake distribution, and a four-valve intake and exhaust system. He acquired a manufacturing license for the Jupiter in 1925.〔Gunston 1989, p.104.〕 In 1927, after inviting two production engineer instructors from the Bristol company,the Jupiter Type 6 of 420 PS and Type 7 of 450 PS with a turbocharger were put into production at the Nakajima factory. After studying the Pratt & Whitney Wasp 9-cylinder radial, Nakajima tried to combine the good points found in Jupiter design with the rational design of the Wasp. Nakajima then produced a series of engine types, named "AA", "AB", "AC", and "AD", as engineering exercises.〔Engine development at Nakajima 1923 - 1945〕 The next engine design, the "AE", was innovative, with a bore of 160 mm and a stroke of 170 mm. Prototypes were made and performance tests were done, but this engine was not adopted due to its very complex engineering. Nakajima continued testing different cylinder designs. In 1929, the "AH" design, with bore and stroke of 146 × 160 mm and a total displacement of 24.1 L, was completed. This was to be the final version of this basic engine design.〔Engine development at Nakajima 1923 - 1945〕 In June 1930 the first prototype of was completed and it passed the durability test for the type approval in the summer. Then flight tests were started using a Nakajima A2N carrier plane. Nakajima had designed the first Japanese originally designed air-cooled 9-cylinder engine, the 450 PS "Kotobuki". In December 1931, this engine was approved and adopted by the Navy for the Navy Type 96 Carrier fighter. The engine was named, in connection with the Jupiter engine, "Kotobuki".〔Engine development at Nakajima 1923 - 1945〕 The "Kotobuki" engine was improved and developed into the "Hikari (light)" engine with the bore and stroke expanded to the limit of the cylinder (160 × 180 mm for a displacement of 32.6 L), with the power was increased to 720 PS. The "Hikari" was used in Type 95 carrier fighters and Type 96 Carrier Attack Plane.〔Engine development at Nakajima 1923 - 1945〕 Nakajima knew that engines of higher power would be needed and began work on a new 14 cylinder design that was based on the 160 × 180 mm cylinder design of the Hikari. The Ha5 prototype engine was completed in 1933, producing 1,000 PS. An improved Ha5 was developed as a 1,500 PS engine. In all about 5,500 Ha5 engines were produced for the military.〔Engine development at Nakajima 1923 - 1945〕 Later on, as the weights of aircraft rose and higher speeds were required, Nakajima continued to improve the Ha-5 design, creating the "Ha-41" and "Ha 109", which shared the same 146mm x 160mm bore and stroke as the Ha-5, but were increased from the 950 hp of the Ha5 to 1,260 hp and 1,440 hp, respectively. The unified code for the Ha-41 was "Ha-34". Later the engine was developed into an 18 cylinder, twin-row engine called the "Ha-219", but this never got past the development phase. All these engines used essentially the same cylinder heads, the differences being in supercharging and engine revolutions per minute. The Ha5 and Ha41 shared the same weight of 630 kg, while the Ha-109 weighed 720 kg due to its larger, twin-stage supercharger system. The Ha-41 was the primary engine of early variants of the Nakajima Ki-49 "Helen" bomber, and the Nakajima Ki-44 "Tojo" fighter, later versions of both planes using the more powerful Ha-109 engine. Early versions of the Mitsubishi Ki-21 "Sally" used the Ha5. The Ha41 would have been an ideal powerplant in aircraft that used the Mitsubishi Kasei, being of smaller dimensions and displacement, yet making equivalent power levels. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Nakajima Ha5」の詳細全文を読む スポンサード リンク
|