The EMD DD35A, also known as the EMD DDA35, was a diesel-electric locomotive of D-D wheel arrangement built by

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Electro-Motive Division exclusively for the

Union Pacific Railroad The Union Pacific Railroad , legally Union Pacific Railroad Company and often called simply Union Pacific, is a freight-hauling railroad that operates 8,300 locomotives over routes in 23 U.S. states west of Chicago and New Orleans. Union Paci ...

. They were a cab-equipped variant of the previous, cabless booster ( B unit) EMD DD35 (sometimes erroneously called the 'DD35B'). Fifteen DD35A locomotives were built between May and July 1965; they were assigned road numbers 70 through 84. This request also led to the introduction of the

ALCO Century 855 The ALCO Century 855 was a model of diesel-electric locomotive built in 1964 by the American Locomotive Company for the Union Pacific Railroad. The locomotive was notable for being ALCO's most powerful diesel-electric locomotive and, at the ti ...

and GE U50. A further development of the 8 axle, twin-engined locomotive produced the final, best known type, the DDA40X "Centennial".

History

Like its cabless predecessor, the DD35A was essentially two EMD GP35 locomotives on a common frame, riding on a pair of 4-

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Flexicoil Flexicoil suspension is a type of secondary suspension for railway vehicles, typically having steel coil springs between the bogie trucks and chassis/frame of a passenger coach, goods freight wagon, or locomotive. Suspension systems using stee ...

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. The cab of a GP35 was fitted to the front end, requiring a longer frame than the DD35; the fuel tank beneath was lengthened, and the center pass-through walkway was offset a little to the rear because of the single cab. Another difference was that the DD35A was fitted with the new flared radiator section EMD was testing on its EMD 645-engined demonstrators (the prototype SD40 demonstrators). The DD35s were initially quite unreliable; some of this was blamed on sand from the internal sandboxes getting in electrical gear, so new sandboxes were fitted on the walkways in 1969. The DD35s were among the last EMD road units to be built with DC generators and old-fashioned switchgear, which were more maintenance intensive than the later AC/DC equipment. Once teething troubles had been overcome, the DD35s were reasonably successful, but they were less flexible than smaller units and thus with the economic downturn of the early 1980s they were withdrawn from service. They spent their final months of service operating around

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before their retirement by 1981. No examples of the DD35 type were preserved.

Original buyers

References

* * * {{EMD SDs Diesel-electric locomotives of the United States DD35A Union Pacific Railroad locomotives D-D locomotives Railway locomotives introduced in 1965 Scrapped locomotives Freight locomotives Standard gauge locomotives of the United States

History

Original buyers

See also

References