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The EMD SD50 is a 3,500-horsepower  locomotive built by General Motors Electro-Motive Division. It was introduced in May 1981 as part of EMD's "50 Series"; production ceased in January 1986. The locomotive was released by the company in the early 1980s and was another attempt to provided a higher-horsepower model to keep pace with General Electric's increasing competition and its C36-7 model that offered more power than the SD40-2.

Unfortunately, EMD rushed the SD50 into production and it not only suffered mechanical problems but also did irreparable damage to the company's reputation as a respectable locomotive builder.  Interestingly, after the issues with the SD50 were corrected the locomotive did prove quite reliable. As a result, many many remain in use today.

The Rio Grande tested the SD50 borrowing four Seaboard System SD50's (8502/8507/8510/8521) which arrived on March 24th 1984 at Pueblo from the MP for a one-week test period. The big gray units were primarily between Pueblo and Craig on coal trains, but they also handled some general freight. The railroad made it a point to use the engines as much as possible in order to obtain a complete analysis of their performance in the difficult mountain terrain. They usually ran in and out of Denver at night but occasionally made daylight appearances on the road, much to the delight of lineside photographers. The cabs always seemed to be well-filled with officials who were compiling test data. Although the Rio Grande has signed a letter of intent with EMD for the purchase of 20 SD40T-2's in the fourth quarter of 1984, it would still be possible for the railroad to switch its order to SD50's instead. Initial reaction to the SD50's was very favorable. The four units were turned over to the Union Pacific at Denver on April 1, 1984 where they will be tested by UP personnel.

Horsepower Wheel Arrangement Gearing Weight Tractive Effort DRGW Class Builder
3500 C-C 70:17 388000 100250 DE C-C ?? EMD

 

Road # EMD Builder # Purchased Year Retired Notes
5501 847022-01 August 1984 June 15, 2007 Renumbered to UP 5095 on 5 September 2001; to UP 9845 on 5 August 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5502 847022-02 August 1984 June 15, 2007 Renumbered to UP 5096 on 27 July 2001; to UP 9846 on 11 June 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5503 847022-03 August 1984 June 15, 2007 Renumbered to UP 9849 on 13 April 2005. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5504 847022-04 August 1984 June 15, 2007 Renumbered to SP 5504; to UP 5098 on 23 June 2001; to UP 9847 on 21 June 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5505 847022-05 August 1984 June 15, 2007 Renumbered to UP 5099 on 18 November 2000; to UP 9848 on 28 May 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5506 847022-06 August 1984 June 15, 2007 Renumbered to UP 5100 on 4 September 2001; to UP 9850 on 26 September 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5507 847022-07 August 1984 June 15, 2007 Renumbered to UP 9851 on 30 August 2005. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5508 847022-08 August 1984 June 15, 2007 Renumbered to UP 5102 on 2 August 2001; to UP 9852 on 30 August 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5509 847022-09 August 1984 June 15, 2007 Repainted in Union Pacific colors and numbered UP 5103. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5510 847022-10 August 1984 June 15, 2007 Repainted in Union Pacific colors and numbered UP 5104. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5511 847022-11 August 1984 June 15, 2007 Renumbered to SP 5511; to UP 5105 on 11 December 2001; to UP 9855 on 15 August 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5512 847022-12 August 1984 June 15, 2007 Renumbered to UP 5106 on 18 February 1998; to UP 9856 on 26 July 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5513 847022-13 August 1984 June 15, 2007 Renumbered to SP 5513 (with D&RGW reporting mark on cab side); to UP 5107 on 11 October 2001; to UP 9857 on 25 July 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5514 847022-14 August 1984 June 15, 2007 Renumbered to SP 5514 in mid 1994 (with D&RGW reporting mark on cab side); to UP 5108 on 13 August 2001; renumbered to UP 9858 on 20 September 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5515 847022-15 August 1984 June 15, 2007 Renumbered by cabside patch to UP 5109 on 3 October 2001; renumbered to UP 9859 on 18 September 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5516 847022-16 August 1984 June 15, 2007 Renumbered to SP 5516 ; to UP 5110 on 14 November 1997; renumbered to UP 9860 on 8 August 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner
5517 847022-17 August 1984 June 15, 2007 Renumbered to SP 5517; to UP 5111 on 5 October 2001; renumbered to UP 9861 on 18 September 2002. Retired by UP on June 15, 2007, upon lease expiration returned to owner

 


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