California's Railroad to the U.S. 1861 - 1996

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Model Train Help EBook

Southern Pacific
Baldwin AS-616B

5 units delivered

5501 5502 5503 5504 5505
4901 4902 4903 4904 4905

#5501 and 5502 delivered in April 1951, were the equivalent of the #5228-5249 order, in that they had the thin frame side of the cast frame, dynamic brakes, and of course were MU capable.

#5501 and 5502 were delivered coupled to #5249 on a Los Angeles bound train - see the Pentrex video "Early Baldwin Diesels on the Southern Pacific" for footage of their delivery run; and assigned to Willits, CA. for duty on the Northwestern Pacific on May 22nd 1951. Although it is perhaps unlikely that they were operated that way, more likely normal operation was just two units.

#5503 - 5505 were delivered in September 1951, and represent the #5250-5278 order of AS-616's, also with dynamic brakes and MU, but with the new thicker frame side of the welded frame.

#5503 - 5505 were some 25 tons heavier, however, dynamometer car tests in 1952 proved, that the extra ballast did not increase tractive efort, on the Baldwins in road service over the Siskiyou's.

September 1955 saw them renumbered to the 4900 series, to allow for deliveries of ALCo RSD-5's.

Originally assigned to Oregon branchlines, by the late 1950's they entered road-service. They were then assigned to hump service in Roseville, Los Angeles and Englewood, after having their gearing changed from 63:15 to the lower 68:15. Three unit 'sets' of Baldwins, were the favored hump power for the 1960's.

#4903 and 4905 are pictured at the Englewood hump, in the 1978-79 SP Motive Power Review

Originally delivered in Tiger Stripe paint with aluminum hood ends, they received the Black Widow scheme when painting was needed after 1954, and then scarlet and gray after 1958.


  • SP Motive Power Annual 1970 - Built by Baldwin article.
  • SP Motive Power Review 1978-79 - Diesels of the TNO.
  • SP Motive Power Review 1983-85 - SP Baldwin Diesels.
  • Extra 2200 South, Issue 58, Oct, Nov, Dec 1976 - SP Roster Part V

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This document © 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008. Richard.A.Percy

Monday, August 30, 1999 10:11:16 PM