EMD GP15. The EMD GP15 is a 4-axle diesel-electric locomotive built by General Motors Electro-Motive Division between June 1976 and April 1983. Intended to provide an alternative to the rebuilding programs that many railroads were applying to their early road switchers, it is generally employed as a yard switcher or light road switcher. There were 3 variants made: the GP15-1, the GP15T, and the GP15AC. The GP15-1 and GP15AC are powered by a 12-cylinder EMD 645E engine, which generates . The GP15T differs in that it uses a turbo charged 8-cylinder instead of the roots blown 12-cylinder to generate the same horsepower. The GP15AC differs from the others as it uses an AC alternator connected to the engine instead of a DC generator to drive the traction motors. The radiator section is similar to those found on the EMD SD40T-2 and EMD SD45T-2 "tunnel motors," leading some observers to incorrectly identify the units as such or as GP15Ts, and giving them the nickname "baby tunnel motors". A number of GP15-1s remain in service today for yard work and light road duty.

History and variants

GP15-1 
The GP15-1 was the most popular variant as it did not contain either of the newer technologies of the other two variants (turbocharging or AC control). EMD built a total of 310 units for American railroads in this variant between June 1976 and March 1982. 

The Missouri Pacific Railroad purchased more units than the other three buyers combined. For spotting purposes, the MP models have a number of visually distinguishing features, though not all were applied consistently to the MP units:

 The MP units have a grab iron ladder mounted on both sides of the long hood end;
 MP's initial order of GP15-1s rode on Blomberg M trucks rather than the more common Blomberg B (all subsequent units were delivered with Blomberg B trucks) — and, while the standard Blomberg B truck carries two brake shoes per wheel, many MP units were equipped with only a single brake shoe per wheel;
 #1555–#1574 were outfitted with the standard 81" nose, while the remaining units (all built in December 1976 or later) came with an 88" nose;

GP15T 

EMD built 28 examples of a variant, the GP15T, between October 1982 and April 1983. It was a very close cousin to the GP15-1, but used a turbocharger in order to generate more power from a smaller engine. Power was provided by an 8-cylinder diesel engine that generated , the same as the GP15-1, but with four fewer cylinders.

28 examples of this locomotive model were built for American railroads. The Chessie System received the majority of them as C&O 1500–1524 (25 units), while the rest went to the Apalachicola Northern Railroad in Florida as AN 720–722 (3 units).

GP15AC 

The GP15AC is a variant built between November and December 1982. This model differs from the GP15-1 due to Missouri Pacific specifying new AR10 AC alternators instead of rebuilt D32 DC generators. The only external difference between the GP15AC and the GP15-1 is a straight side sill (shared with the EMD GP15T) not related to the transmission difference.

34 examples of this locomotive model were built in total: 30 for Missouri Pacific Railroad, and four for Venezuela's IFE.

Rebuilds 
Union Pacific has rebuilt 22 of their GP15-1's into GP15N's at their Jenks shop. These units received a microprocessor control system to increase adhesion, control options, and extend the life of the locomotive.

Preservation 
In 2021, CSX donated GP15T #1507 (built 1982 as C&O #1507) to the B&O Railroad Museum in Baltimore, Maryland. It is the first GP15 class locomotive to be preserved.

References

Further reading
 Sperandeo, Andy. "The EMD GP15-1: EMD's down-sized road switcher." Model Railroader, January 1990, 110–115.

External links

 EMD GP15T Operator's Manual
 Sarberenyi, Robert. EMD GP15-1, GP15AC, and GP15T Original Owners

B-B locomotives
GP15-1
Diesel–electric locomotives of the United States
Railway locomotives introduced in 1976
Freight locomotives
Standard gauge locomotives of the United States