ALCO HH series

ALCO HH series

Portland Terminal Company HH600 #1004, photographed at Portland, Maine in 1968.

Type and origin Power type Diesel-electric Builder ALCO Total produced HH600: 79; HH660: 43 ; HH900: 21; HH1000: 34

Specifications AAR wheel arr. B-B Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Wheel diameter 40 in (1,016 mm) Length 45 ft 2 3⁄4 in (13.79 m) Prime mover HH600/900: McIntosh & Seymour 531; HH660/1000: McIntosh & Seymour 538 Engine type Inline-6 Four stroke engine diesel Aspiration HH600/660: Naturally aspirated; HH900/1000: Turbocharged Displacement 9,572 cu in (156.86 L) Cylinders 6 Cylinder size 12.5 in × 13 in (318 mm × 330 mm)

Performance figures Power output 600 hp (447 kW), 660 hp (492 kW), 900 hp (671 kW), or 1,000 hp (746 kW)

The ALCO HH series were an early series of switcher diesel-electric locomotives built by the American Locomotive Company (ALCO) of Schenectady, New York between 1931 and 1940, when they were replaced by the S series; the 660 hp (490 kW) S-1 and 1,000 hp (750 kW) S-2. They were ALCO's first diesel switchers to enter true series production, and among the very first land vehicles anywhere to utilise the revolutionary diesel-electric power transmission.

The "HH" name stood for "High Hood", a name ALCO came eventually to use in an official context, but originally an unofficial name. Model designations such as HH600 are only semi-official. Original ALCO designations were either descriptive or based on the internal order/design number.

A total of 177 of the HH series were produced; this comprised one prototype and four production models of varying power outputs.

The first HH series locomotive, ALCO demonstrator #600 was mechanically almost identical to the others, but the appearance differed. The sides of the locomotive's hood sloped outward from top to bottom, and brake equipment was exposed beneath the cab. After a period of demonstration on a number of railroads, the unit was sold to the New York, New Haven and Hartford Railroad who numbered it as 0900, this number often being used to describe the locomotive, although the classification on the builder's data card was "404-OE-200". It rode on a unique pattern of trucks. This first unit was built in July 1931.

The locomotive was equipped with a four-stroke McIntosh & Seymour 531 straight-6 diesel engine, powering a General Electric GT551A1 main generator. Four nose-suspended GE-287-D traction motors in the trucks were geared at a ratio of 4.25:1 to the wheels; the motors were cooled by electrically driven traction motor blowers.