Southern Pacific EMD SD7 1427, October 14, 1975, location unknown. Photographer: R H Heuerman.

(Craig Garver, Public domain, https://www.flickr.com/photos/digitalrailartist/51693717168/in/photolist-2mH2wpG-2mKZP8E-2kT5uM3-2kTdjRb-2kkU4Da-2kT6Yn8-2kT5qJX)

EMD SD7 DIESEL-ELECTRIC LOCOMOTIVE

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.

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.

Southern Pacific EMD SD7 1420 at San Jose, California, November 4, 1973. Photographer: W. L. Hammond.

(Craig Garver, Public domain, https://www.flickr.com/photos/digitalrailartist/51660101646/)

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.

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.

Denver & Rio Grande Western EMD SD7 5301 at Denver, Colorado, February 16, 1977. Photographer: Bruce Black.

(Craig Garver, Public domain, https://www.flickr.com/photos/digitalrailartist/51117476107/)

Rebuilds

SD7R
The Southern Pacific Transportation Company had rebuilt a total of 42 of their SD7 locomotives into the EMD SD7R.

Original buyers

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

(N9002U, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons)

Preservation

• The first SD7 (later converted into an SD7R) built by EMD, Southern Pacific 1518 (demonstrator No. 990), is preserved in operational condition at the Illinois Railway Museum.
• Southern 197 is preserved at the Virginia Museum of Transportation. It was originally built as Central of Georgia 201.
  The Dakota Southern Railway rosters two SD7's, No. 512, and No. 522 (512 and 522 are ex-MILW No. 2212 and No. 2222). No. 512, currently still serves with the Dakota Southern Railway, but 522 has since been scrapped.
• Burlington Northern No. 6008, one of the first 20 SD7s to be built in 1952, is preserved and in restoration to its original appearance as Great Northern No. 558 at the Minnesota Transportation Museum.
• Former Pennsylvania Railroad No. 8589 is in operation at Red Trail Energy in Richardton, ND, as No. 1751 with a chopped nose.
• Nevada Northern Railway No. 401 is in service at one of LADWP's power plants in Delta, Utah. When retired, it will be donated to the Nevada Northern Railway Museum, as part of an agreement.
• Portland and Western had rostered SD7 No. 1501 (Ex-SP 5280) in Albany, Oregon, as of January 2022. No. 1501 retains its scarlet and gray paint and functional oscillating gyralite. This locomotive was retired July 19, 2023, and was originally scheduled to be scrapped by its parent company Genesee and Wyoming Inc. as part of a fine resolution agreement with the EPA. But it was eventually acquired by Dieselmotive Company, Inc. (BUGX) and is currently awaiting arrival to the Dieselmotive Company Inc. as of 2023.

SP 1518 at the Illinois Railway Museum.

(Nate Beal, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons)

Overview

Type and origin
Power type: Diesel-electric
Builder: General Motors Electro-Motive Division (EMD)
Model: SD7
Build date: May 1951 – November 1953
Total produced: 188
Specifications
Configuration:
​• AAR C-C
Gauge: 4 ft 8+1⁄2 in (1,435 mm) standard gauge
Trucks: EMD Flexicoil C
Wheel diameter: 40 in (1,016 mm)
Minimum curve: 23° (250 ft (76.20 m) radius)
Wheelbase: 48 ft 7 in (14.81 m)
Length: 61 ft 2+3⁄4 in (18.66 m)
Width: 10 ft 8 in (3.25 m)
Height: 15 ft 4+1⁄2 in (4.69 m)
Locomotive weight: 309,000 lb (140,000 kg)
Fuel capacity: 1,200 US gal (4,500 L; 1,000 imp gal)
Prime mover: EMD 567B
RPM range: 800
Engine type: V16 diesel engine
Aspiration: Roots-type supercharger
Displacement: 9,072 cu in (148.66 L)
Generator: D-12-C
Traction motors: (6) D-27-B
Cylinders: 16
Performance figures
Power output: 1,500 hp (1.12 MW)
Tractive effort: 77,250 lbf (343,600 N)
Career
Locale: United States
Disposition: Some still in service, others preserved

See Also:

EMD Diesel-Electric Locomotives

GM Electro-Motive Division

Diesel-Electric Locomotives