The H12-44 proved as Fairbanks Morse's most successful diesel locomotive with nearly 400 constructed over an eleven year period. Despite the fact that its diesels used a complicated opposed-piston prime mover a number of railroads came to like them for their incredible lugging ability and relative light weight. This particular model looked quite similar to its predecessor, the H10-44, save for a slight increase in horsepower. While FM was able to sell a number of a diesels through its Canadian Locomotive Company arm it had difficulty finding sales to many foreign lines although a few did purchase their products. As it turned out the H12-44 had one of the longest production runs of any FM model and so many were produced that at least sixteen domestic examples remain preserved today.
It seems FM fell into the same situation as American Locomotive and Baldwin; while the builder found sustained with its switchers the company failed to catalog an effective road-switcher. Electro-Motive had the market all but locked up and had no true competitor until General Electric beginning in the late 1950's.
The H12-44 began production during May of 1950 following the earlier H10-44. Railroads had liked this switcher and apparently were just after increased horsepower as the H12-44 sold even better. It came equipped with a standard Fairbanks Morse 2-cycle 38D8 1/8 opposed piston prime mover that could produce 1,200 horsepower using a B-B truck setup (meaning two axles per truck). The carbody styling was again inspired by noted industrial designer Raymond Loewy. However, to reduce production costs FM simplified the design in the fall of 1952 removing many of the styling features Loewy had suggested. It did not really take away from the model's attractiveness although the locomotive did sport a more basic, boxy appearance.
The FM H12-44 carried roughly the same tractive effort as models being offered at the time by both Electro-Motive Division (EMD) and the American Locomotive Company (Alco); 61,000 pounds starting and 34,000 pounds continuous. Thanks to the locomotive's relatively light-weight the H12-44 was ideal for use in both yard/switcher service and could also be used in light freight service with its respectable horsepower rating. FM's classification system somewhat resembled Balwin's initial system, although somewhat more simplified. In regards to the H12-44; the “H” stood for Hood unit, “12” was for 1,200 horsepower, and each 4 meant four axles and four traction motors.
Overall the locomotive sold 369 units in the U.S./Canada by the time production had ended in March of 1961 making it the manufacturer's most successful. The Santa Fe certainly liked the switcher as the company wound up with 59 examples employing them heavily in light duty work. Generally FM models sold relatively poorly although it is not necessarily because Fairbanks Morse's models in general were unreliable, as was usually the case with Alco (early on anyway) and particularly Baldwin. Reliability with FM's diesel locomotives has often been questioned but I believe the issue was mostly due to the fact that FM's opposed-piston prime mover was difficult to maintain and far different from the standard designs being offered by the other builders.
For instance, in regards to the Train Master, it has been noted by John Kirkland in his book The Diesel Builders Volume 1 that the locomotives performed admirably for more than 20 years on the Southern Pacific due to a maintenance team that understood the model, despite taking a daily beating in freight service. In any event, the H12-44 was purchased by a little more than a dozen Class I systems including industries Ayrshire Collieries, U.S. Steel - Fairless Works, Yankeetown Dock, and the Tennessee Valley Authority. Even the U.S. Army bought the locomotive, 20 to be exact! FM's Canadian arm also built 30 for Canadian National Railway as well as an A1A-A1A design known as the H12-46. CN ultimately wound up with 30 examples of the variant built during the early 1950s.
It should be noted that another variant was manufactured as well, the H12-44TS for the Santa Fe numbered 541, 542, and 543. The AT&SF requested the locomotive for use in shuttling passenger trains and equipment around its Dearborn Station terminal in Chicago. The locomotive was somewhat longer at 54 feet, 2 inches and featured the addition of a short hood ahead of the cab giving it the appearance of a road switcher. However, it still offered 1,200 horsepower and a B-B truck arrangement. Santa Fe regularly employed the three units in yard service until 1972 when the were sold. Today, #543 is preserved at the Illinois Railway Museum. In any event, a photo of 543 is presented below pushing the Super Chief into Dearborn Station on October 14, 1972.