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A red locomotive in a freight yard
B&M S-5 #864 in Boston in September 1965
Type and origin
Power type Diesel-electric
Builder ALCO
Serial number 80915–80921
Model S-5 (Specification DL421 and DL421A)
Build date June 1954
Total produced 7
AAR wheel arr. B-B
Gauge 4 ft 8 12 in (1,435 mm)
Prime mover ALCO 251
Cylinders Straight 6
Performance figures
Power output 800 hp (600 kW)

The Alco S-5 (DL 421A) was a diesel-electric locomotive of the switcher type 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[edit]

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

See also[edit]

External links[edit]

Media related to ALCO S-5 locomotives at Wikimedia Commons