Ferrocarril del Pacifico Alco S6 722 at Sufragio, Sinaloa, Mexico, February 25, 1978. Photographer: Paul Hunnell.

"You know, it just doesn't get much better than this for roster photography. Freshly outshopped from Empalme, a few kilometers north, a turntable, period equipment,

a stunningly beautiful Sonoran/Sinaloan sky, and beautiful desert background. And, a thoroughly excellent photographer!" - Craig Garver

ALCO S-6

The Alco S-6 (specification DL 430) was a diesel-electric switcher locomotive constructed by ALCO of Schenectady, New York; a total of 126 locomotives were built between May 1955 and December 1960. The S-6 was an improved version of the earlier S-5.

Southern Pacific Alco S-6 No 1271 at Newhall, CA, May 1966.

(Drew Jacksich from San Jose, California Republic, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons)

Design

Visually indistinguishable from the S-5, the S-6 used an ALCO 251A or 251B prime mover rated at 900 horsepower (670 kW). The locomotive rode on two-axle AAR trucks, giving a B-B wheel arrangement. ALCO produced a cow-calf variant for the Oliver Iron Mining Company designated SB-8/SSB-9, two sets were produced of this version.

Original owners

Railroad Quantity Road Numbers Notes
Allied Chemical Company 1 110
ARMCO Steel 1 1202
B. Perini & Sons Construction Company 1 101 to Upper Merion and Plymouth Railroad 101
Belt Railway of Chicago 1 420
Ferrocarril Chihuahua al Pacífico 1 60 Renumbered 106
Cia Fundidora de Hierro y Acero 3 1-3
Ferrocarril del Pacífico 24 701–723
Ferrocarriles Nacionales de México 1 5300
Northern Pacific Railway 1 750 to Burlington Northern Railroad 950
Ohio River Company (ORCo) 1 56
Republic Steel 3 153, 317, 318
Secretaria de Comunicaciones de Obras Publicas (SCOP) 3 7133-1, 2, 3 to Ferrocarril del Sureste (same numbers)
Sheffield Steel 2 15, 16
Southern Pacific Railroad 70 1033–1082, 4634–4645 renumbered 1200–1257, 1270–1281
South Buffalo Railway 6 40–45
Tennessee Copper 1 107
Upper Merion and Plymouth Railroad 1 61
U.S. Pipe and Foundry 1 38
Columbia Geneva Steel 1 1
Western Maryland Railway 2 151, 152
Ferrocarriles Unidos de Yucatán 1 301

Southern Pacific Alco S-6 No. 1085 at San Jose, CA, August 1964.

(Drew Jacksich from San Jose, California Republic, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons)

In popular culture

In Back to the Future Part III, two double headed S-6 locomotives destroyed the DeLorean time machine, when it returned to 1985.

ALCO S-6 Overview

Type and origin
Power type: Diesel
Builder: ALCO
Model: S-6
Build date: May 1955–December 1960
Total produced: 126
Specifications
Configuration:
​• AAR: B-B
• UIC: Bo′Bo′
Gauge: 4 ft 8+1⁄2 in (1,435 mm)
Length: 45 ft 5 in (13.84 m)
Width: 10 ft (3.05 m)
Height: 14 ft 8 in (4.47 m)
Loco weight: 230,000 lb (104.3 tonnes)
Fuel capacity: 635 US gal (2,400 L; 529 imp gal)
Lubricant capacity: 140 US gal (530 L; 120 imp gal)
Coolant capacity: 110 US gal (420 L; 92 imp gal)
Sandbox capacity: 26 cu ft (0.74 m3)
Prime mover: Alco 251A or B
RPM range: 375–1000 rpm
Engine type: Four-stroke diesel
Generator: GE GT-533 (or GE GT-584)
Traction motors: 4 × GE 731 (GE 752 optional)
Cylinders Straight: 6
Cylinder size: 9 in × 10+1⁄2 in (229 mm × 267 mm)
Performance figures
Maximum speed: 60 mph (97 km/h)
Power output: 900 hp (670 kW)
Career
Locale: United States, Mexico

See Also: