EMD F7

History

The F7 was the fourth model in GM-EMD's successful line of F unit locomotives, and by far the best-selling cab unit of all time. In fact, more F7's were built than all other F units combined. It succeeded the F3 model in GM-EMD's F unit sequence, and was replaced in turn by the F9. Final assembly was at GM-EMD's La Grange, Illinois, plant or GMD's London, Ontario, facility.

The F7 differed from the F3 primarily in internal equipment (mostly electrical) and some external features. Its continuous tractive effort rating was 20% higher (e.g. 40,000 lb (18,000 kg) for an F7 with 65 mph (105 km/h) gearing, compared to 32,500 lb (14,700 kg) for an F3 with the same gearing.

A total of 2,366 cab-equipped lead A units and 1,483 cabless-booster or B units were built. (Note: the B unit is often referred to as an "F7B", whereas the A unit is simply an "F7".)

Many F7s remained in service for decades, as railroads found them economical to operate and maintain. However, the locomotive was not very popular with yard crews who operated them in switching service because they were difficult to mount and dismount, and it was also nearly impossible for the engineer to see hand signals from a ground crew without leaning way outside the window. As most of these engines were bought and operated before two-way radio became standard on most American railroads, this was a major point of contention. In later years, with the advent of the "road switchers" such as the EMD GP7, F units were primarily used in "through freight" and "unit train" service where there was very little or no switching to be done on line of road.

Engine and powertrain

The F7's prime mover is a 16-cylinder 567B series Diesel engine developing 1,500 hp (1.1 MW) at 800 rpm. The 567B is a mechanically aspirated two-stroke design in a 45 degree Vee configuration, with 567 cu in (9.29 L) displacement per cylinder, for a total of 9,072 cu in (148.66 L).  A direct current generator that is mechanically coupled to the flywheel end of the engine powers four traction motors, with two motors mounted on each Blomberg B truck. EMD has built all of its major components since 1939. Starting in August 1953 EMD installed 567BC and 567C engines in a few F7s, see roster below.

Identification

There are no easily identifiable differences between late F3 production and early F7 production; the major differences were all internal electrical system changes. However, no F7 had "chicken wire" grilles of most F3s, and no F3s had later F7 changes described below under Phases.

The F9 is distinguishable from the late F7 by having five, rather than four, carbody center louver groups covering the carbody filters. The additional one is placed ahead of the first porthole, where F7s have no openings. The F9's greater power output, of course, cannot be seen from the outside.

There were also two main classes of F7's: passenger and freight. Most passenger units had upper and lower headlights, but this wasn't always the rule. Many freight units had the upper Mars or Pyle brand warning light as well. And some passenger units only had a single upper headlight, ie the Pennsylvania. Many units had the upper lights plated over later in life, or the door light removed/plated over and the Mars/Pyle light removed. These early warning lights had lots of moving linkages and a motor that were high maintenance for the shops.

Phases

The identification of locomotive "phases" is a creation of railfans, although now used in Diesel Spotters Guide. EMD used no such identification, and instead kept track of the marketing name (F7) and individual locomotives' build numbers. During the production cycle of a model, EMD would often make detail changes that were not readily apparent to the casual observer. To keep better track of the variations of locomotives identified the same by the manufacturer, railfans began referring to phases (critical changes to a locomotive line).

Despite not being official designations, the phase description is useful. However, many of the changes described are cosmetic, easily changed features of a locomotive: e.g., roof fans, body panels, grilles and the like could be and sometimes were updated or swapped. Most of the phase differences on the F7 were concerned only with A units; B units varied far less. The following are normally identified as F7 phases:

Phase I (early)

Built from February 1949. Upper grille with horizontal openings. Four horizontal louvred openings on center body panel. 36-inch (914 mm) dynamic brake fan, if dynamic brakes fitted. Flush windshield gasket changed to raised in July 1949. Square cab door corners with kick plates on the steps beneath. Wing window short with square corners. Single drip strip over cab windows and door. Square end door window. Round sand filler cover. Rear overhang.

Phase I (late)

Built from March 1950. Upper grille started out horizontal, as in early Phase I; from March 1951, some locomotives were built with vertical-slotted "Farr-Air" grilles, and by October 1951, all had them. Cab doors became round-cornered, and the kick plates were deleted. The wing windows became taller, with round corners. Two drip strips; one over cab windows, second over door. The end door window became round after November 1950.

Phase II

Built from February 1952. All upper grilles vertical "Farr-Air" type. Center car body louvres became vertical-slotted. Sand filler now with a horizontal, rectangular pull handle. From June 1952, 48-inch (1,219 mm) dynamic brake fans began to be introduced; from October 1952, all dynamic-brake equipped locomotives had them. At that latter date, locomotives no longer had a rear overhang.

Rebuilds

Several F7s were rebuilt by Morrison-Knudsen as F9PHs and used in passenger operations. Others were rebuilt as the "FP10" and used by the Massachusetts Bay Transportation Authority. In addition, the Santa Fe had 190 of their F7As rebuilt into CF7 hood units in the 1970s. Only one original unit from the railway exists to this day.

Preservation