ALCO S-6

The ALCO S-6, specification DL 430, was a diesel-electric switcher locomotive built by ALCO at Schenectady, New York, with 126 constructed between May 1955 and December 1960. It was an improved version of the earlier S-5 and visually indistinguishable from it. It used an ALCO 251A or 251B prime mover rated at 900 horsepower and rode on two-axle AAR trucks in a B-B arrangement. ALCO also built a cow and calf variant for the Oliver Iron Mining Company, designated SB-8 and SSB-9, of which two sets were produced. In popular culture, two double-headed S-6 locomotives destroy the DeLorean time machine in Back to the Future Part III.