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ALCO S-5

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ALCO S-5
A red locomotive in a freight yard
B&M S-5 #864 in Boston in September 1965
Type and origin
Power typeDiesel-electric
BuilderALCO
Serial number80915–80921
ModelS-5 (Specification DL421 and DL421A)
Build dateJune 1954
Total produced7
Specifications
Configuration:
 • AARB-B
Gauge4 ft 8+12 in (1,435 mm)
Prime moverAlco 251
CylindersStraight 6
Performance figures
Power output800 hp (600 kW)
Career
OperatorsBoston and Maine Railroad
Numbers860-865, 909
LocaleUnited States
Disposition1 preserved, remainder scrapped

The Alco S-5 (DL 421A) was a diesel-electric switcher locomotive rated at 800 horsepower (600 kW), that rode on two-axle trucks, having a B-B wheel arrangement.

This was Alco's second attempt to build a replacement 251-engined switcher to replace the 539-engined S-3 and S-4. Only seven were sold. The demonstrator unit was ALCO specification DL421 and the six production units were ALCO specification DL421A. Alco fitted the 251A engine in its replacement, the S-6 with power output raised by 100 horsepower (75 kW).

Original owners

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Railroad Quantity Road numbers Notes
Alco (demonstrator) 1 909 to Island Creek Fuel and Transportation Company #102
Boston and Maine Railroad 6 860–865

See also

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Media related to ALCO S-5 locomotives at Wikimedia Commons