EMD F-unit

The FT, introduced in 1939 with the new 567 engine and Blomberg B trucks, was a successful design, and remained in production during WWII. The F3 (1946) had a different roof arrangement that included the replacement of the FT's boxy dynamic brake structure with two under-roof grids, two exhaust stacks instead of four, and four cooling fans grouped together instead of separated pairs of cooling fans. The F3 was also longer than the FT to allow a standard draft gear to be installed at the rear of the unit. The 567B engine was uprated to . Some F3s were nicknamed "chickenwire" for the type of engine room air-intake structure along the sides. The F7 (1949) and F9 (1954) were evolutionary: the F7 had improved traction motors, the F9 had a 567C engine. A louver arrangement over the vents changed their appearance from the F3. There were also versions, the FP7 and FP9, the extra length being used to house a tank for extra water capacity. Only one F model did not have Blomberg B trucks: the FL9 electro-diesel locomotive had a lightweight Flexicoil B in front and a standard passenger A-1-A at the rear. Model descriptions are as built, but EMC/EMD locomotives are often rebuilt to newer standards. ==Engine and powertrain==

The F series used a 16-cylinder version of the 567 series diesel engine, introduced in 1939. The 567 was designed specifically for railroad locomotives, a mechanically aspirated 2 stroke 45 degree V type with displacement per cylinder, for a total of . An ongoing engine improvement program saw the FT's original up-rated to in the FL9 by the end of F unit production. A DC generator powered four traction motors, two on each truck. The Blomberg B truck first used in the FT became the EMD production standard, being used until 1995. EMC/EMD built all of its major components after 1939. ==Passenger service==

No. 113, an EMD FP7, leading two EMD SDP40Fs with the San Francisco Zephyr at the Yuba Gap in 1975 While the F-unit series was originally conceived for freight service, many were used to haul passenger trains. The original EMC FT demonstrator was equipped with a steam generator in the B units for train heating. Several railroads took advantage of the large space in the rear of their B units to add steam generators. The first FTs built strictly as a passenger unit was the Santa Fe 167 four unit set in February 1945. Learning from that, EMD offered an optional steam generator on all later F unit models. It was mounted at the rear of the car body; steam-generator equipped locomotives can be recognized 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 (16 versus 12) and thus had less chance of overloading the traction motors. Additionally, the four F-unit set had all its weight on driven wheels and was thereby capable of greater tractive effort. The AT&SF Super Chief, CB&Q/D&RGW/WP California Zephyr, and GN Empire Builder all used F units on their Chicago-West Coast routes in the 1950s. The F7 was also popular for commuter lines and other passenger service where the trains were short. ==Options==

There were several options that could be specified by customers for the F-units, such as type and mounting location of horns and bells. Dynamic brakes Dynamic brakes were an option on F units ordered by railroads operating in mountainous terrain and with steep grades. Passenger or freight pilot Either a passenger or freight style pilot could be ordered. The passenger pilot, similar to that standard on E-units, slopes smoothly down from the bottom of the nose, making a single slope all the way down from the headlight. The coupler is retractable with concealing doors. The result is a very attractive appearance that enhanced the impression of a powerful and speedy machine. The freight pilot curves 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 is fixed and protrudes through a rectangular opening in the pilot. ==Licensees==

Locomotives based on the F7 design were built by licensees in Europe and Australia. ==See also==