EMD F-units were a line of Diesel-electric locomotives produced between November 1939 and November 1960 by General Motors Electro-Motive Division and General Motors-Diesel Division. Final assembly for all F-units was at the GM-EMD plant at La Grange, Illinois and the GMDD plant in London, Ontario. They were sold to railroads throughout the United States, Canada, Mexico and a few were exported to Saudi Arabia. The term F-unit refers to the model numbers given to each successive type, all of which began with F.
F-units were originally designed for freight service, although many hauled passenger trains. Almost all F-units were B-B locomotives; they ran on two Blomberg B two-axle trucks with all axles powered. The prime mover in F-units was a sixteen cylinder EMD 567 series mechanically aspirated two-stroke Diesel engine, progressing from model 16-567 through 16-567D.
Structurally, the locomotive was a carbody unit with the body as the main load-bearing structure, of a bridge-truss like design, and covered with cosmetic panels. The so-called bulldog nose was a distinguishing feature of the locomotive's appearance, and made a lasting impression in the mind of the traveling public.
The F-units were the most successful "first generation" road Diesel locomotives in North America, and were largely responsible for the replacing of the steam locomotive in road freight service.
F-units were sometimes known as covered wagons, due to the similarity in appearance of the roof of an F-unit to the canvas roof of a Conestoga wagon, an animal-drawn wagon used in the westward expansion of the United States during the late 18th and 19th centuries. When a train's locomotive consist included only F-units, the train would then be called a wagon train. These two usages are still popular with the railfan community.
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| Model designation | Build year | Total produced | AAR wheel arrangement | Prime mover | Power output | Image |
|---|---|---|---|---|---|---|
| FT | 1939–1945 | 555 A units, 541 B units |
B-B (B-B+B-B with B unit) |
EMD 16-567 EMD 16-567A |
2,700 hp (with B unit) |
|
| F2 | 1946 | 74 A units, 30 B units |
B-B | EMD 16-567B | 1,350 hp (1000 kW) |
|
| F3 | 1946–1949 | 1,111 A units, 696 B units |
B-B | EMD 16-567B | 1,500 hp (1,100 kW) |
|
| F7 | 1949–1953 | 2,366 A units, 1,483 B units |
B-B | EMD 16-567B | 1,500 hp (1,100 kW) |
|
| FP7 | 1949–1953 | 381 A units | B-B | EMD 567B | 1,500 hp (1,200 kW) |
|
| F9 | 1953–1960 | 99 A units, 156 B units |
B-B | EMD 16-567C | 1,750 hp (1200 kW) |
|
| FP9 | 1954–1959 | 90 A units, no B units |
B-B | EMD 567C | 1,750 hp (1,300 kW) |
|
| FL9 | 1956–1960 | 60 | B-A1A | EMD 567C or EMD 567D1; plus 660V DC (3rd rail) |
567C: 1,750 hp (1,300 kW); 567D1: 1,800 hp (1,340 kW) |
While the F-unit series was originally conceived for freight service, many were used to haul passenger trains. The original FT, as delivered, did not contain a steam generator for train heating, but a large empty space in the rear of their B units was used to add one on several railroads. Learning from this, EMD offered an optional steam generator on the F3 and later models. This was mounted at the rear of the carbody; steam-generator equipped locomotives can be recognised by the exhaust stack and safety valves protruding at the rear of the roof.
The F units were popular passenger locomotives on mountain grades (where they were recommended by EMD), because a four-unit set had more motored axles than a trio of E-units of equivalent power (sixteen versus twelve) and thus had less chance of overloading the traction motors. Additionally, that 4-unit F set had all its weight on driven wheels and was thereby capable of greater tractive effort. The F7 was also popular in passenger service for commuter services and other service where the trains were short.
There were several options that could be specified by ordering railroads, such as type and mounting location of horns, bells, and the like.
Dynamic brakes were an option on F units ordered by railroads with mountainous terrain and heavy grades.
Either a passenger or freight style pilot could be ordered. The passenger pilot, similar to that standard on EMD E units, sloped smoothly down from the bottom of the nose, making a single slope all the way down from the headlight. The coupler was retractable with concealing doors. The result was a very attractive appearance that enhanced the impression of a powerful and speedy machine.
The freight pilot curved inward a little way below the bottom of the nose before sloping out again, to give more clearance to the coupler and hoses. The coupler was non-retractable and protruded through a rectangular opening in the pilot.
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