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The EMD SD90MAC is a 〔http://web.archive.org/web/20011210220002/http://www.gmemd.com/en/locomotive/na_freight/sd90mac/index.htm〕 C-C diesel-electric hood unit locomotive produced by General Motors Electro-Motive Division. It is, with the SD80MAC, one of the largest single-engined locomotives produced by that company, surpassed only by the dual-engined DD series. The SD90MACs feature radial steering trucks with AC traction motors and an isolated safety cab which is mounted on shock absorbers to lessen vibrations in the cab. The SD90MAC, like the SD80MAC, SD70ACe, and SD70M-2, has a wide radiator section, nearly the entire width of the locomotive, which along with their size makes them easy to spot. ==History== The SD90AC was introduced in 1995, along with the SD80MAC locomotives. The SD90MAC was designed to utilize the new 16-cylinder H-engine, while the SD80MAC was designed to use the 20-cylinder version of the existing 710G engine. However, technical problems with the engine resulted in the first locomotives being shipped with 16-cylinder 710G engines, making them similar to the SD70MACs. These locomotives were given the informal model designation SD9043MAC by railroads that purchased them with the option to re-engine them with engines when they became available. This upgrade program, however, was never taken advantage of by SD90MAC buyers due to reliability issues with the newer engine. Over 400 SD90MAC locomotives fitted with the 710 engine were built. In 1996, EMD entered full production on their , 16-cylinder H-engine, and all SD90MACs made from then on used that for its prime mover. Locomotives fitted with this engine are sometimes referred to as SD90MAC-H locomotives. Later versions of the SD90MAC-H feature a Phase II cab, with a new nose which offers higher visibility from the cab than the old nose. The SD90MAC-H did not prove popular with railroads and less than 70 were built, including EMD demonstrator units. Since the SD90MAC-H had such a large prime mover, it didn't offer the same operational flexibility as smaller units, limiting its possible customer base to only the largest railroads. Also, since the H-engine was a new design it hadn't reached the same level of reliability as EMD's previous engine. The low reliability on such a large engine was an especially bad combination since the loss of one engine in a train meant the loss of a larger percentage of pulling power than had a smaller engine failed. In the end the SD90MAC-H was only delivered to two railroads, the Union Pacific Railroad and the Canadian Pacific Railway.〔 The Canadian Pacific locomotives were part of an earlier order for 710 equipped SD90MAC locomotives that was still in production when EMD switched over to the H-engine. EMD also tried offering a lower-power version of the SD90MAC with a 12-cylinder engine called the SD89MAC, but none were produced other than the prototype. 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「EMD SD90MAC」の詳細全文を読む スポンサード リンク
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