EMD F-unit

EMD F-units were a line of diesel locomotives produced between November 1939 and November 1960 by General Motors' Electro-Motive Division. Final assembly for all F-units was at the GM-EMD plant at La Grange, Illinois. They were sold to railroads throughout the United States, Canada and Mexico. The term F-units refers to the model numbers given to each successive type, all of which began with F. The F stood for "freight"; F-units were originally designed for freight service, although some hauled passenger trains. 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 567 series diesel engine progressing from model 16–567 thru 16–567C.

F-units were sometimes known as covered wagons. 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. The origin of these terms comes from the similarity in appearance of the roof of an F-unit to the canvas roof of a Conestoga wagon, which was an animal-drawn wagon used in the westward expansion of the United States, during the late 1700s and 1800s.

The F-units were the most successful "first generation" road diesel locomotives in North America, and were the locomotives largely responsible for replacing steam locomotives in heavy road freight service. Some are still in operation.

Models

• FT (1939-1945) 1,350 hp/unit, 555 A units, 541 B units built
• F2 (1946) 1,350 hp/unit, 74 A units, 30 B units built
• F3 (1945-1949) 1,500 hp/unit, 1111 A units, 696 B units built
• F7 (1949-1953) 1,500 hp/unit, 2366 A units, 1483 B units built
• FP7 (1949-1953) 1,500 hp/unit, 378 A units built
• F9 (1954-1957) 1,750 hp/unit, 87 A units, 154 B units built
• FP9 (1954-1959) 1,750 hp/unit, 79 A units built
• FL9 (1956-1960) 1,750/1,800 hp/unit, 60 A units built

Passenger service

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 them. Additionally, that 4-unit F set had all its weight on driven wheels and thus was capable of a greater tractive effort.

The F7 was also popular in passenger service for commuter services and other service where the trains were short.

Options

There were several options that could be specified by ordering railroads, in addition to the smaller customisable items that could always be specified like horns, bells and the like.

Dynamic brakes

Dynamic brakes were an option on F units ordered by railroads with mountainous terrain and heavy grades, and their presence was indicated by an additional roof fan near the front of the locomotive.

Passenger or freight pilot

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 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.

References

• Marre, Louis A. (1995). Diesel Locomotives: The First 50 Years. Kalmbach Publishing Co. ISBN 0–89024–258–5.
• Pinkepank, Jerry A. (1973). The Second Diesel Spotter’s Guide. Kalmbach Books. Library of Congress Catalog Card No. 66–22894.
• Solomon, Brian (2000). The American Diesel Locomotive. MCI Publishing Company. ISBN 0–7603–0666–4.