The EMD SD7 is a model of 6-axle

diesel locomotive A diesel locomotive is a type of railway locomotive in which the prime mover (locomotive), power source is a diesel engine. Several types of diesel locomotives have been developed, differing mainly in the means by which mechanical power is con ...

built by General Motors Electro-Motive Division between May 1951 and November 1953. It had an EMD 567B 16-

cylinder A cylinder () has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infinite ...

engine producing for its six traction motors. United States railroads bought 188 units. This was the first model in EMD's SD ''(Special Duty)'' series of locomotives, a lengthened B-B

GP7 GP-7 or GP7 may refer to: Vehicular * EMD ''GP7'', a class of locomotives * Ducati ''GP7'', a model of the racing motorcycle Ducati ''Desmosedici'' * Honda ''GP7'', a model of the subcompact Honda ''Fit Shuttle'' Other uses * (48616) 1995 GP7, a ...

with a C-C truck arrangement. The two extra axles and traction motors are useful in heavy, low-speed freight service. EMD continues to produce SD series locomotives to this day. Some SD7s both high and short-hood can still be found in service today on shortline railroads and industrial operators, although most Class I roads stopped using these locomotives by the 1970s and 1980s.

Design and production

The SD7 was conceived as a modification of the existing

EMD GP7 The EMD GP7 is a four-axle (AAR wheel arrangement#B-B, B-B) diesel-electric locomotive built by General Motors Electro-Motive Division and General Motors Diesel between October 1949 and May 1954.Pinkepank, Jerry A. (1973) pp. 53 The GP7 was ...

with two additional powered axles, one for each

truck A truck or lorry is a motor vehicle designed to transport freight, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame construct ...

. Providing two more axles served two purposes: it gave the locomotive more tractive effort compared to the four-axle GP7, and it distributed the locomotive's weight more evenly. EMD produced its first examples of the SD7 in May 1951, using the 567B engine. Starting in August 1953 a total of 26 SD7s were produced which used either the 567BC engine or the 567C engine. SD7s were originally set up to run long hood forward, usually noted by the letter "F" painted adjacent to the top step of the long hood boarding steps. Many were later changed or upgraded to run short hood forward as is today's Association of American Railroads standard. EMD ended production in November 1953 and began producing the SD7's successor, the SD9, in January 1954.

Rebuilds

SD7R

The

Southern Pacific Transportation Company The Southern Pacific (or Espee from the railroad initials) was an American Class I railroad network that existed from 1865 to 1996 and operated largely in the Western United States. The system was operated by various companies under the names ...

had rebuilt a total of 42 of their SD7 locomotives into the EMD SD7R. They were numbered 1500–1542. The rebuilds had also included upgrades to the

electrical systems Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwel ...

traction motor A traction motor is an electric motor used for propulsion of a vehicle, such as locomotives, electric vehicle, electric or hydrogen vehicles, or electric multiple unit trains. Traction (engineering), Traction motors are used in electrically powe ...

s, as well as a changeout of the prime movers swapping the 16-cylinder 567B prime movers with 16-cylinder 645CE prime movers.

Original buyers

Preservation

Currently preserved

Burlington Northern The Burlington Northern Railroad was a United States–based railroad company formed from a merger of four major U.S. railroads. Burlington Northern operated between 1970 and 1995. Its historical lineage begins in the earliest days of railroad ...

#6008 (ex- Great Northern #558) is preserved at the

Minnesota Transportation Museum The Minnesota Transportation Museum (MTM, reporting mark MNTX) is a transportation museum in Saint Paul, Minnesota, United States. MTM operates several heritage transportation sites in Minnesota and one in Wisconsin. The museum is actively involv ...

Saint Paul, Minnesota Saint Paul (often abbreviated St. Paul) is the List of capitals in the United States, capital city of the U.S. state of Minnesota and the county seat of Ramsey County, Minnesota, Ramsey County. As of the 2020 United States census, 2020 census, ...

. #6008 was one of the first 20 SD7s to be built in 1952; it's currently under restoration to its original appearance as Great Northern #558. * Southern #197 is preserved at the

Virginia Museum of Transportation The Virginia Museum of Transportation (VMT) is a museum in Downtown Roanoke, Virginia, that is devoted to the topic of transportation. History The Virginia Museum of Transportation began in 1963 as the Roanoke Transportation Museum in Wasena ...

. It was originally built as

Central of Georgia The Central of Georgia Railway started as the Central Rail Road and Canal Company in 1833. As a way to better attract investment capital, the railroad changed its name to Central Rail Road and Banking Company of Georgia. This railroad was constr ...

#201. *Southern Pacific #1518 (ex-EMD demonstrator #990), is preserved in operational condition at the

Illinois Railway Museum The Illinois Railway Museum (IRM, reporting mark IRMX) is the largest railroad museum in the United States. It is located in the Chicago metropolitan area at 7000 Olson Road in Union, Illinois, northwest of downtown Chicago. Overview ...

. #1518 was the first SD7 (later converted into an SD7R) built by EMD. * Portland and Western formerly rostered SD7 #1501 (Ex-SP #5280), which was retired in 2023 as part of a fine resolution agreement with the EPA. *The Dakota Southern Railway rosters one SD7, #512 (ex- MILW #2212) *ILSX #1751 (ex-

Pennsylvania Railroad The Pennsylvania Railroad ( reporting mark PRR), legal name as the Pennsylvania Railroad Company, also known as the "Pennsy," was an American Class I railroad that was established in 1846 and headquartered in Philadelphia, Pennsylvania. At its ...

#8589) is in operation at Red Trail Energy in Richardton, ND. *

Nevada Northern Railway The Nevada Northern Railway was a railroad in the U.S. state of Nevada, built primarily to reach a major copper producing area in White Pine County, Nevada. The railway, constructed in 1905–06, extended northward about from Ely, Nevada, Ely to ...

401 is in service at the

Intermountain Power Plant Intermountain Power Plant is a large coal-fired power plant at Delta, Utah, US. It has an installed capacity of 1,900 MW, is owned by the Intermountain Power Agency, and is operated by the Los Angeles Department of Water and Power. The p ...

Delta, Utah Delta is the largest city in Millard County, Utah, Millard County, Utah, United States. It is located in the northeastern area of Millard County along the Sevier River and is surrounded by farmland. The population was 3,622 at the 2020 United St ...

. When retired, it will be donated to the

Nevada Northern Railway Museum The Nevada Northern Railway Museum is a railroad museum and heritage railroad located in Ely, Nevada, owned by the State of Nevada and operated by a historic foundation dedicated to the preservation of the Nevada Northern Railway. Museum ac ...

, as part of an agreement with the museum.

References

External links

Locomotive Truck EMD FlexiCoil C
{{EMD SDs SD07 C-C locomotives Diesel–electric locomotives of the United States Railway locomotives introduced in 1952 Freight locomotives Standard-gauge locomotives of the United States Baltimore and Ohio locomotives Chicago and North Western Railway locomotives Chicago, Burlington and Quincy locomotives Denver and Rio Grande Western Railroad locomotives Great Northern Railway (United States) locomotives Milwaukee Road locomotives Pennsylvania Railroad locomotives Southern Pacific Railroad locomotives Union Pacific Railroad locomotives