EMD SD7
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 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

The 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]

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]

Design and Production

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.[3]

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 had rebuilt a total of 42 of their SD7 locomotives into the EMD SD7R.[4][5]

Original buyers

OwnerQuantityNumbersNotes
Electro-Motive Division2 990to Southern Pacific 5308 then 2715 to 1415 ne 1518
991to Baltimore and Ohio 760
Baltimore and Ohio Railroad4761–764These units were built with the 567BC engine.
Bessemer and Lake Erie Railroad8451–455, 801–803
Chicago and North Western Railway51660–1664
Chicago, Burlington and Quincy Railroad37300–324, 400–411322-324 were built with the 567BC engine. To Burlington Northern 6023-6059
Chicago, Burlington and Quincy Railroad (Colorado and Southern Railway)10810–819To Burlington Northern 6070-6079
Chicago, Burlington and Quincy Railroad (Fort Worth and Denver Railway)11850–860858-860 were built with the 567BC engine. To Burlington Northern 6080-6090
Chicago, Milwaukee, St. Paul and Pacific Railroad242200–2223Renumbered 500–523, 2215-2223 were built with the 567BC engine.
Central of Georgia Railway1201
Denver and Rio Grande Western Railroad55300–5304
Great Northern Railway23550–572To Burlington Northern 6000-6022
Kennecott Copper Corporation1903
Minneapolis and St. Louis Railway2852, 952Renumbered 300–301. To Chicago and North Western Railway.
Nevada Northern Railway1401Sold to LADWP in the 1980s; reacquired by Nevada Northern in 2021, along with RSD-4 #201.[6]
Pennsylvania Railroad28588–8589These units were built with the 567BC engine
Southern Pacific Company425279–5293, 5309–53355321-5323, 5334-5335 were built with the 567C engine
Union Pacific Railroad10775–784
Total188

Preservation

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

References

  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. Schafer, Mike (1998). Vintage diesel locomotives. Osceola, WI: Motorbooks International. pp. 36–37. ISBN 0-7603-0507-2. OCLC 38738930.
  4. Withers (1995), p. 5
  5. Shine (1991), p. 9-56, 186
  6. "Bring 401 and 201 Home".
  7. "G&W locomotives to scrap or upgrade per EPA decree in 2023". Trains.com. Retrieved 27 January 2023.
  8. "Diesel Motive Company". www.thedieselshop.us. Retrieved 2023-10-13.

Additional Reading

  • Strapac, Joseph A. (1997). Southern Pacific Historic Diesels Volume 4, SD7 and SD9 Locomotives (1st ed.). Shade Tree Books, Bellflower, California. ISBN 9780930742171. OL 8360777M.
  • Withers, Paul K. (1995). Diesel Era, November/December 1995, Volume 6 Number 6. Withers Publishing.
  • Shine, Joseph (1991). SP into the '90's. Four Ways West Publications. ISBN 9780685752104.
  • Shine, Joseph (1988). SP 1987/88 Motive Power Pictorial (1st ed.). Four-Ways West Publications. ISBN 9780961687434.
  • Signor, John R. (2005). SP Trainline - Issues 83-93 (1st ed.). Southern Pacific Historical & Technical Society.
  • Dorin, Patrick C. (1972). Chicago and North Western Power. Burbank, California: Superior Publishing. p. 114. ISBN 0-87564-715-4.
  • Pinkepank, Jerry A (1973). The Second Diesel Spotter's Guide. Kalmbach Books. pp. 17, 26, 71–72. ISBN 0-89024-026-4. LCCN 66-22894.
  • Sarberenyi, Robert. "EMD SD7 Original Owners". www.trainweb.org. Retrieved 2006-08-27.
  • Diesel Era Volume 6 Number 6 November/December 1995, "EMD's SD7" by Paul K. Withers pp 5–20; 47–50.
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