The EMD SD7 is a model of 6-axle diesel locomotive built by General Motors Electro-Motive Division between May 1951 and November 1953. It had an EMD 567B 16-cylinder engine producing 1,500 horsepower (1.12 MW) for its six traction motors. United States railroads bought 188 units.[1]

EMD SD7
SP #1518 inside Barn 9 at the Illinois Railway Museum in Union, Illinois on May 27, 2023.
Type and origin
Power typeDiesel-electric
BuilderGeneral Motors Electro-Motive Division (EMD)
ModelSD7
Build dateMay 1951 – November 1953
Total produced188
Specifications
Configuration:
 • AARC-C
Gauge4 ft 8+12 in (1,435 mm) standard gauge
TrucksEMD Flexicoil C
Wheel diameter40 in (1,016 mm)
Minimum curve23° (250 ft (76.20 m) radius)
Wheelbase48 ft 7 in (14.81 m)
Length61 ft 2+34 in (18.66 m)
Width10 ft 8 in (3.25 m)
Height15 ft 4+12 in (4.69 m)
Loco weight309,000 lb (140,000 kg)
Fuel capacity1,200 US gal (4,500 L; 1,000 imp gal)
Prime moverEMD 16-567B
RPM range800
Engine typeV16 diesel engine
AspirationRoots-type supercharger
Displacement9,072 cu in (148.66 L)
GeneratorD-12-C
Traction motors(6) D-27-B
Cylinders16
Performance figures
Power output1,500 hp (1.12 MW)
Tractive effort77,250 lbf (343,600 N)
Career
LocaleUnited States
DispositionSome still in service, others preserved

This was the first model in EMD's SD (Special Duty) series of locomotives, a lengthened B-B GP7 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.[2][3]

Design and production

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The SD7 was conceived as a modification of the existing EMD GP7 with two additional powered axles, one for each truck. 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.[4]

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

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SD7R

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The Southern Pacific Transportation Company 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, traction motors, as well as a changeout of the prime movers swapping the 16-cylinder 567B prime movers with 16-cylinder 645CE prime movers.[5][6]

Original buyers

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Image Owner Quantity Numbers Notes Ref.
Electro-Motive Division 2 990 to Southern Pacific 5308 then 2715 to 1415 ne 1518 [7]
991 to Baltimore and Ohio 760
Baltimore and Ohio Railroad 4 761–764 These units were built with the 567BC engine.
Bessemer and Lake Erie Railroad 8 451–455, 801–803
Chicago and North Western Railway 5 1660–1664
  Chicago, Burlington and Quincy Railroad 37 300–324, 400–411 322-324 were built with the 567BC engine. To Burlington Northern 6023-6059
Chicago, Burlington and Quincy Railroad (Colorado and Southern Railway) 10 810–819 To Burlington Northern 6070-6079
  Chicago, Burlington and Quincy Railroad (Fort Worth and Denver Railway) 11 850–860 858-860 were built with the 567BC engine. To Burlington Northern 6080-6090
  Chicago, Milwaukee, St. Paul and Pacific Railroad 24 2200–2223 Renumbered 500–523, 2215-2223 were built with the 567BC engine.
Central of Georgia Railway 1 201
Denver and Rio Grande Western Railroad 5 5300–5304
Great Northern Railway 23 550–572 To Burlington Northern 6000-6022 [8]
Kennecott Copper Corporation 1 903
Minneapolis and St. Louis Railway 2 852, 952 Renumbered 300–301. To Chicago and North Western Railway.
Nevada Northern Railway 1 401 Sold to LADWP in the 1980s; reacquired by Nevada Northern in 2021, along with RSD-4 #201. [9]
Pennsylvania Railroad 2 8588–8589 These units were built with the 567BC engine
Southern Pacific Company 42 5279–5293, 5309–5335 5321-5323, 5334-5335 were built with the 567C engine
Union Pacific Railroad 10 775–784
Total 188

Preservation

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PNWR 1501 working in PNWR's yard in Albany, Oregon, on January 20, 2022

Currently preserved

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References

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  1. ^ Pinkepank, Jerry A (1973). The Second Diesel Spotter's Guide. Kalmbach Books. p. 71. LCCN 66-22894.
  2. ^ Guss, Chris (May 16, 2023). "EMD's pioneering SD7 and SD9 locomotives". Trains Newsletter. Kalmbach Media. Retrieved May 16, 2023.
  3. ^ Solomon, Brian (2014). GE and EMD Locomotives: The Illustrated History. Voyageur Press. p. 249. ISBN 978-0-7603-4612-9.
  4. ^ Schafer, Mike (1998). Vintage diesel locomotives. Osceola, WI: Motorbooks International. pp. 36–37. ISBN 0-7603-0507-2. OCLC 38738930.
  5. ^ Withers (1995), p. 5
  6. ^ Shine (1991), p. 9-56, 186
  7. ^ a b "Trains". Trains Magazine. September 1997. pp. 66–68.
  8. ^ "Great Northern Empire - Then and Now". www.greatnorthernempire.net. Retrieved 2024-05-16.
  9. ^ "Bring 401 and 201 Home".
  10. ^ "Minnesota museum acquires Great Northern SD7 | Trains Magazine". Trains. 2018-03-14. Retrieved 2024-05-16.
  11. ^ "G&W locomotives to scrap or upgrade per EPA decree in 2023". Trains.com. Retrieved 27 January 2023.
  12. ^ Franz, Justin (2021-09-29). "Nevada Northern Raising Money to Bring Two Historic Diesels Home". Railfan & Railroad Magazine. Retrieved 2024-03-09.

Further reading

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