page_title: ALCO HH series
section_title: Diesel-electric power transmission
hierarchical_section_title: ALCO HH series / ALCO 600 (New Haven #0900) / Diesel-electric power transmission
caption_attribution_description: English: Photo of the first Alco 600 locomotive built, from an ad for Alco diesel locomotives in Railway Age.
context_page_description: The ALCO HH series were an early series of switcher diesel-electric locomotives built by the American Locomotive Company of Schenectady, New York between 1931 and 1940, when they were replaced by the S series; the 660 hp S-1 and 1,000 hp S-2. They were ALCO's first diesel switchers to enter true series production, and among the very first land vehicles anywhere to use 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.
context_section_description: 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.
caption: The New Haven's Alco 600 in 1933.
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