The HH series were the first diesel shunting locomotives that ALCO mass-produced in large numbers. They were also among the first land vehicles with a diesel-electric transmission. “HH” stood for “High Hood” while the number stood for the engine power in hp. The first HH600 demonstrator was sold to New Haven after testing in 1931. In 1934, industrial designer Otto Kuhler revised the shape of the locomotive body, giving it more rounded corners.

HH600 No. 913 of the New Haven on a 1938 ALCO advertising brochure

ALCO

The first variant had a McIntosh & Seymour 531 with six cylinders. It wasn't until 1937 that the HH900 followed with a turbocharged variant of this engine. In 1938 the HH660 followed with the slightly more powerful naturally aspirated engine of the 538 series and from 1939 finally the HH1000 with the turbocharged variant of the engine of the 538 series. A total of 177 locomotives were built, of which the HH600 was the most successful with 79 units due to its long production period. The individual railway companies operated a maximum of twelve of each model.

The DL-103 to DL-110 were the first diesel locomotives built by ALCO. The DL only stood for “Diesel Locomotive” and the individual models hardly differed from each other. The odd numbers stood for normal locomotives with cabs (so-called A-units), while the even numbers denoted the cab-less B-units or boosters. As with most American diesel locomotives of the time, the carbody was designed as a self-supporting construction with a streamlined front. The shape of the front with the three-piece windshield was designed by the German-American industrial designer Otto Kohler. All locomotives had an output of 2,000 hp, which came from two six-cylinder inline prime movers with turbochargers. Although four traction motors were sufficient to transmit the power, three-axle bogies, each with a carrying axle in the middle, were used, as in the EMD E series.

A total of 74 A units and four B units were built between 1939 and 1945. By far the largest proportion of these were the 60 A units ordered by the New York, New Haven & Hartford Railroad. All other customers received a maximum of four units, which were often used in front of prestigious passenger trains. The Second World War had made procurement difficult, since the production of purely passenger locomotives was prohibited and locomotives that were equally suitable for freight and passenger trains were also difficult to obtain. Finally, the New Haven only used their locomotives to haul passenger trains during the day, while hauling freight trains at night. Between 1949 and 1951 they were modernized and, among other things, the side windows in the engine room were removed, which were only used for decorative purposes. Despite this, the locomotives' service life was not very long, as they were soon replaced by more modern locomotives. Some were still visually matched to their EMD competitors, but most fell victim to the scrap press in the 1950s.

In 1940, Rock Island approached ALCO and ordered a new type of diesel locomotive that would be equally suitable for switching and road service. Instead of the cab units that were widespread at the time, a locomotive with a load-bearing frame and narrower hoods was developed, also known as the “hood unit”. The resulting design was characterized by the fact that there was an unobstructed field of vision when driving in both directions. This meant that it could be used without restrictions for switching, but also in road service without any cutbacks. It was usually running with the long hood ahead, even if this meant a poorer overview. Thus the new breed of road switchers was created, which was soon adopted by all North American manufacturers.

A total of 466 examples of the RS-1 were completed at ALCO and three more at the Montreal Locomotive Works by 1960. This is the longest production run of any diesel locomotive for the North American market to date, and also meant that they continued in production for several years after their successors were discontinued. The first locomotives, which were actually intended for Rock Island, were delivered to the US Army due to the USA entering the war.

Although a steam generator was available as an option, the RS-1 was rarely used in front of passenger trains. In freight service, with its 1,000 hp, it was primarily used on branch lines. The large six-cylinder ALCO 539T proved to be very durable, with many examples still being used in the 21st century. The RSD-1 and RSC-1 were developed as six-axle developments for lighter rails, with the latter only four axles being driven.

Southern Railway RS-3 No. 2027, together with a combined passenger and baggage car and an EMD FTB converted to a heating car, formed a commuter train in October 1967 in Warrenville, South Carolina

Roger Puta

The RS-2 was built between 1946 and 1950, with 368 examples being built at ALCO and nine in Montreal. It differed from the RS-1 mainly in the new 244 series V12 engine with 1,500 hp and a slightly more rounded body. The new prime mover did not prove to be as reliable in use as the old one. 64 pieces were delivered to Mexico and 46 to Brazil. The locomotives for Brazil had a gauge of 1,600 mm.

The RS-3 achieved the highest number of units, of which 1,272 were built between 1950 and 1956, with 146 units coming from Montreal. It was created at a time when Fairbanks-Morse and Baldwin were also bringing their road switchers from 1,500 to 1,600 hp to keep up with competitor EMD. 98 engines went to Canadian customers and 46 to Brazil. Here, too, a six-axle variant with four powered axles was developed as the RSC-3.

To overcome the reliability problems of the 244 series prime mover, 98 RS-3s were rebuilt between 1972 and 1978 with EMD 567 engines. The engines, including the fan system, came from decommissioned EMD E8s. These were named RS-3m to distinguish them. A few of these are still in use in 2022, although some RS-3s that have not been converted have survived into the 21st century.

During the Second World War, the Soviet Union ordered high-traction diesel locomotives from the USA via the Lend-Lease Act. These should be used primarily in the southern parts of the country, where only little water was available for the operation of steam locomotives. In response, ALCO equipped the RS-1 with two additional powered axles. Despite the same engine power, a higher starting tractive effort was now available, but a decreasing power with increasing speed.

70 RSD-1s were sent to the Soviet Union via the Trans-Iranian Railway, with 12 engines already falling victim to submarines at sea. There they were given the designation Д^A20 (D^A20), which stood for “Diesel, ALCO, 20 tonnes axle load”. They served there as a basis for the ТЭ1 and its successors. Another 87 locomotives went to the US Army and six to the Ferrocarriles Nacionales de México.

36 RSD-4 were built in 1951 and 1952, based on the RS-3. They had the new 244 series engine with 1,600 hp and were all delivered to US customers. Since the generator was considered too weak, the RSD-5 was built with a new generator from 1952. A total of 167 RSD-5s were built for US customers and 37 for Mexico.

With the development of the new Type 244 engine, ALCO introduced the PA passenger locomotive in addition to the FA freight locomotive in 1946. Not only did the propulsion electrics come from General Electric, the streamlined and modern design of the car body also came from Ray Patten, head of GE's design department. The PA got the more powerful sixteen-cylinder engine and stood on two bogies with the A1A wheel arrangement. What all PA and FA have in common is that black smoke came out when accelerating due to the lack of air in the turbo lag.

With a 2,000 hp engine, 169 PA1 and 39 PB1 without a cab were built. From 1950 onwards, 81 PA2 and eight PB2 were built with 2,250 hp. Three PA-2s went to Brazil with a gauge of 5 ft 3 in. Some railroads also used their PA and PB in freight traffic, but the number of units remained behind EMD's E series due to lower reliability. The Massachusetts Bay Transit Authority used its locomotives until the late 1970s and then sold them to the Ferrocarriles Nacionales de México, which continued to use them until 1981.