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Alco's "HH" Series: Its Early Switchers

Last revised: August 26, 2024

By: Adam Burns

The American Locomotive Company (Alco), a name synonymous with steam locomotives, played a transformative role in the transition to diesel-electric power in the railroad industry during the early 20th century.

Among its pioneering efforts was the development of the HH, or so-called "High Hood," series of diesel switchers, a significant milestone in the evolution of railroad technology.

Interestingly, as John Kirkland notes in his book, "The Diesel Builders: Volume II, American Locomotive Company and Montreal Locomotive Works," Alco never classified these early types - equipped with the builder's model 531 and 538 engines - as "High Hoods."

This term was coined by railfans years later following Alco's introduction of the low-profile hood on the 'S' series switchers to differentiate the two types.

The HH series, known for its distinctive design and innovative features, offered a glimpse into the future of rail transport and set the stage for subsequent developments in diesel locomotives.

Santa Fe HH1000 #2312 lays over at the First Street Yard in Los Angeles during the 1960s. This early Alco switcher was built in June, 1939 and remained on the AT&SF roster until March, 1971. American-Rails.com collection.

Genesis

Alco's entry into the diesel-electric market has been well-documented.  It constructed the mechanical components for a GE-design, 70-ton straight-electric in 1903.

This little engine was built for the Buffalo & Lockport Railroad, a 24-mile interurban.  Then, between 1917-1924 Alco partnered with GE and Ingersoll-Rand.

In 1923 the group turned out a 300 horsepower boxcab given #8835 (GE's construction number) that featured an I-R model PR, six-cylinder in-line diesel engine.  It began demonstration testing on June 9, 1924 and eventually returned to GE's Erie, Pennsylvania plant on July 9, 1925 following 2227.5 hours of work.

Following the successful test of this little switcher, the three companies began a limited run of boxcab diesels through the mid-1920s.  Despite steam remaining king at this time, the Schenectady builder felt strongly enough about the diesel's future it acquired engine-builder McIntosh & Seymour Corporation of Auburn, New York in 1928 to continue development of this technology.

Alco's first stand-alone diesel locomotive was boxcab switcher #300 completed in January, 1931.  The 300 horsepower, double-ended cab switcher was eventually sold to Jay Street Connecting Railroad as #300.

Design and Technical Features

After continuing to produce a handful of end-cab switchers, what would be described as Alco's first "High Hood" variant was 600 horsepower demonstrator #600 (which became New Haven #0900), completed in June, 1931.

What enthusiasts would later dub the "HH600" series this end-cab model was the first to feature M&S's model 531 prime mover.   Externally, the locomotive featured a higher hood and heavily tapered along each side.   This was a significant change from the earlier end-cab types.

However, the next demonstrator, #601 (which became Lehigh Valley #105), boasted an even higher hood, nearly to the top of the cab - but less tapered - which required moving the bell to the hood's end for clearance purposes.

The locomotive's front was designated as the cab end with the long hood the rear.  The early HH600 was followed by the more powerful HH660, HH900, and HH1000 models. The numerical designations indicated the horsepower ratings of the engines—600, 660, 900, and 1000 horsepower respectively. 

Several key technical features distinguished the HH series:

1. **Engine Technology**: The HH series utilized inline six-cylinder model 531, 531T, and 538 diesel engines developed by McIntosh & Seymour, which Alco later acquired. These engines were robust and reliable, providing the power necessary for the demanding switching operations in rail yards and industrial settings.

2. **Electrical Systems**: The locomotives employed electrical components from GE, including traction motors and generators. The diesel engine drove an electric generator, which in turn powered the traction motors connected to the locomotive's axles.

This diesel-electric propulsion system offered several advantages over steam, including smoother power delivery and better tractive effort at low speeds. 

Among demonstrator #600's components included a GE model CP26 air compressor, model GT526 main generator, and four GE287D traction motors. 

It was equipped with 16:68 gearing, 40" wheels, a continuous tractive effort of 28,000 pounds at 4.8 mph, and could operate at maximum speeds of 40 mph.  It entered service on the New Haven on August 3, 1931 at the Bell Dock Yard in New Haven, Connecticut.

3. **Construction**: The HH series featured a boxy, utilitarian design with a high central hood that housed the diesel engine and other components. The design provided good visibility for the operator, which was crucial for switching operations that required frequent maneuvering and reversing.

4. **Blunt Trucks": Demonstrator #601 was the first to feature Alco's new Blunt Truck, designed by engineer James G. Blunt.  The design's odd appearance when negotiating poor and uneven track gave it the nickname "Rubber Truck" although it proved quite adept in such applications.

Erie Lackawanna HH600 #323, still in its Delaware, Lackawanna & Western scheme (built as #406), is seen here in Jersey City, New Jersey on June 23, 1964. The DL&W owned eight of these early, 600 horsepower Alco switchers, #401-408, that were acquired between 1933 and January, 1934 (#401 was originally Alco demonstrator #603). Although Alco never gave these early switchers a model name, railfans later adopted the "HH" designation, an acronym for "High Hood." American-Rails.com collection.

Operational Impact and Adoption

The HH series quickly gained traction among railroads, owing to its operational efficiency and cost-effectiveness. These locomotives proved particularly useful in switching operations, where the frequent starting and stopping inherent to steam engines posed significant challenges.

Major railroads, including the New York Central, the Baltimore and Ohio, and the Delaware, Lackawanna & Western, were among the early adopters of the HH series.

The locomotives were employed in a variety of roles, ranging from yard switching to industrial shunting and light freight duties. Their versatility and reliability cemented their reputation as effective workhorses in the railroad industry.

Legacy and Technological Advances

While the HH series was eventually succeeded by more advanced designs, its impact on the dieselization of American railroads was profound. The lessons learned from the development and operation of these early diesel switchers informed subsequent generations of locomotive design, both at Alco and within the industry at large.

Several key advancements emerged from the HH series:

1. **Refinement of Diesel-Electric Technology**: The successful implementation of diesel-electric propulsion in the HH series validated the technology and encouraged further innovation. The principles established in the HH series were refined and expanded upon in later locomotive models.

2. **Influence on Locomotive Design**: The boxy, high-hood design of the HH series influenced the aesthetic and functional design of future diesel locomotives. While later models adopted lower hoods and other refinements, the HH series set a precedent for practical, utilitarian design in switching locomotives.

3. **Impact on Railroad Operations**: The operational success of the HH series demonstrated the tangible benefits of diesel power in terms of efficiency, cost savings, and operational flexibility. This success accelerated the widespread adoption of diesel locomotives, leading to the gradual phasing out of steam engines.

Specifications

Production Rosters

HH600

HH660

HH900

HH1000

Santa Fe HH1000 #2316, an early Alco switcher completed in June, 1939 (and capable of producing 1,000 horsepower), is seen here carrying out work at Los Angeles Union Passenger Terminal in March, 1947. This unit was later sold to Precision National in June, 1971. Russ Cole photo. American-Rails.com collection.

Conclusion

The HH series of diesel switcher locomotives by Alco represents a pivotal chapter in the history of railroad technology. As one of the earliest and most influential diesel-electric locomotive designs, the HH series played a crucial role in the transition from steam to diesel power in American railroads.

Its innovative features, operational efficiency, and versatility laid the groundwork for subsequent advancements in locomotive design and set the stage for the dieselization of railroads worldwide.

Alco's HH series not only showcased the potential of diesel-electric technology but also underscored the importance of collaboration and innovation in the pursuit of progress.

By blending Alco's locomotive construction expertise with GE's electrical engineering capabilities, the HH series emerged as a remarkable achievement that left an enduring legacy in the annals of railroad history.