EMD GP9
The EMD GP9 is a four-axle, B-B configuration road switcher diesel-electric locomotive manufactured by General Motors' Electro-Motive Division (EMD) primarily between January 1954 and October 1959, powered by a 16-cylinder 567C prime mover rated at 1,750 horsepower.[1][2] A total of 4,092 GP9 units were produced by EMD, with an additional 165 cabless GP9B booster units built until December 1959, while General Motors Diesel (GMD), EMD's Canadian subsidiary, constructed 646 units for Canadian operators.[1][2] Measuring 56 feet 2 inches in length and weighing approximately 249,000 pounds, the GP9 featured dynamic braking, optional steam generators for passenger service, and a top speed of up to 90 miles per hour depending on gearing.[1] Introduced as part of EMD's "9 Line" of second-generation diesels, the GP9 succeeded the earlier GP7 model by incorporating enhancements such as improved cylinder head design for better reliability and higher horsepower output, addressing limitations in the GP7's 1,500-horsepower engine.[1] The first GP9, numbered 2400, was delivered to the Milwaukee Road in early 1954, marking a significant step in the transition from steam to full dieselization on North American railroads.[1] Its versatile design made it suitable for both freight hauling and yard switching, with B-B trucks equipped with D37 traction motors providing strong tractive effort for heavy loads.[1][2] The GP9 saw widespread adoption among Class I railroads, including the Norfolk & Western, Union Pacific, and Southern Pacific, as well as numerous short lines and regional carriers across the United States and Canada, with some units exported to Mexico, Venezuela, and Peru.[1][2] Production extended into 1963 for certain orders, and the model influenced successors like the GP18 (1,800 hp) and GP20 (2,000 hp), but its robust construction ensured longevity, with many units rebuilt and remaining in service on tourist railroads, museums, and industrial operations into the 21st century.[1][2]Design and Specifications
Engine and Powertrain
The EMD GP9 utilized the model 16-567C as its prime mover, a 16-cylinder, two-stroke, uniflow scavenged diesel engine that delivered 1,750 horsepower (1,300 kW) at a maximum of 835 rpm. This engine featured a bore of 8.5 inches (216 mm) and a stroke of 10 inches (254 mm), resulting in a total displacement of 9,072 cubic inches (148.7 L).[3] The 567C represented an upgrade from the GP7's 567B engine, boosting output by 250 horsepower through refinements in cylinder head design, fuel injection, and overall engine efficiency, while retaining Roots blower aspiration.[1] Power from the prime mover was transmitted via a General Motors D12 main generator directly coupled to the engine's flywheel, which converted mechanical energy into electrical power for propulsion. This electricity powered four GM D37 series DC traction motors, two per Blomberg B truck, in a B-B wheel arrangement that provided reliable adhesion for road-switching duties.[1] The system yielded a starting tractive effort of 62,000 lbf (276 kN) and a continuous tractive effort of 40,000 lbf (178 kN) at typical gear ratios like 62:15.[1] Dynamic braking was fitted as standard equipment on the GP9, marking a key advancement for operational efficiency.[4] In this system, the traction motors functioned as generators during deceleration, converting kinetic energy back into electrical current that was dissipated as heat through onboard resistor grids, thereby reducing reliance on air brakes and improving control on steep grades.[4] The locomotive's fuel tank held 1,600 US gallons (6,056 L) of diesel, sufficient for extended service intervals typical of mid-20th-century rail operations.[5] Supporting the 567C engine's thermal management, the cooling system employed two engine-driven centrifugal pumps to circulate water through replaceable inlet manifolds and individual cylinder liners, with a total capacity of 227 US gallons (860 L) routed to a heat exchanger or radiator assembly for efficient heat rejection.[6]Physical Characteristics
The EMD GP9 was a hood-type diesel locomotive featuring a high-short-hood forward cab design, which positioned the engineer's operating compartment at the front with a relatively low-profile short hood ahead of it for improved visibility. This cab retained an arched roof profile inherited from earlier EMD switcher designs, while the long hood extended rearward to house the prime mover and auxiliary equipment. The overall structure emphasized durability and serviceability, with the locomotive's body constructed primarily of welded steel for rigidity.[7] In terms of dimensions, the GP9 measured 56 feet 2 inches (17.12 m) in length over the pulling faces of the couplers, 10 feet 3 inches (3.12 m) in width, and 14 feet 6 inches (4.42 m) in height from the rail to the top of the cab. Its standard operating weight was 249,000 pounds (113,000 kg), which could vary slightly depending on optional equipment.[1] Production of the GP9 incorporated evolutionary changes in external detailing, distinguishing Phase I units built in 1954 from Phase II units produced from 1955 to 1959. Phase I examples featured louvers on the first two tall engine room doors, GP7-style louver arrangement on generator room doors (4 right, 3 left), and pipe handrail stanchions. Phase II locomotives added louvers to the third tall engine room door, reduced louver sets on generator room doors, and used channel handrail stanchions for improved durability. These modifications reflected refinements in ventilation and safety without altering the core cab or hood proportions.[7] The running gear consisted of four-axle AAR Type B trucks, specifically EMD's Blomberg B design, which provided B-B wheel arrangement with swing hangers for enhanced stability on uneven track. Each truck was equipped with 40-inch (1,016 mm) diameter wheels and a 9-foot (2.74 m) wheelbase, contributing to a low center-of-gravity height of approximately 72 inches above the rail for optimal hauling performance. The distance between truck centers spanned 31 feet 0 inches (9.45 m).[8] Standard features included a Westinghouse Schedule 6-L air brake system, which integrated an H-6 automatic brake valve with self-lapping independent controls for reliable train handling. Certain units intended for passenger service were fitted with a steam generator in the short hood extension, capable of producing hot water or steam for train heating, though this was optional and absent on most freight-dedicated examples.[1][9]Production
Timeline and Manufacturing
The EMD GP9 entered production in January 1954 at Electro-Motive Division's (EMD) primary manufacturing facility in LaGrange, Illinois, directly succeeding the earlier GP7 model as part of EMD's General Purpose (GP) series of road-switcher locomotives.[1] This marked the beginning of a significant production run that emphasized improved reliability and power output over its predecessor, with assembly focused on streamlining the four-axle B-B truck configuration for versatile freight and yard service.[7] In mid-1956, production transitioned from Phase I to Phase II units, incorporating design refinements such as updated louver placements on the engine room doors and modifications to the air reservoir piping for enhanced durability and maintenance access.[10] These changes were applied progressively during the build process at LaGrange, reflecting iterative improvements based on field feedback from early units. U.S. production concluded in December 1959, with a total of 3,446 units completed at the Illinois plant before shifting focus to successor models like the GP18.[11] Parallel production occurred at General Motors Diesel (GMD), EMD's Canadian subsidiary, which operated under licensing agreements to manufacture GP9s tailored for North American export markets. GMD's facility in London, Ontario, began building the model in 1954 and continued through August 1963, producing 646 units primarily for Canadian railroads. These builds included minor adaptations, such as high short-hood configurations requested by operators like Canadian National and Canadian Pacific for improved crew protection, as they commonly ran long-hood forward, a common practice in Canada.[12]Output and Variants
The EMD GP9 saw substantial production during its manufacturing run, with a total of 4,092 cab-equipped units built between 1954 and 1963, comprising 3,446 units from the Electro-Motive Division (EMD) in LaGrange, Illinois, and 646 units from the General Motors Diesel (GMD) division in London, Ontario.[11][13] In addition, 165 cabless booster units designated as GP9Bs were produced exclusively by EMD.[11] The GP9B was a hoodless booster variant designed to operate in multiple-unit sets with cab-equipped GP9s, sharing the same 1,750 horsepower EMD 16-567C prime mover but lacking a cab for crew accommodation to reduce weight and cost.[11] These units were built only by EMD from February 1954 to October 1957, with primary orders from the Union Pacific (75 units) and Pennsylvania Railroad (40 units), among others.[13][14] Factory options for the GP9 included variations in short hood height to suit operational needs. Most U.S.-built units featured a low short hood to enhance forward visibility for crew members operating in either direction, while Canadian GMD-built GP9s standardized a high short hood for improved crew protection against potential collisions.[11][15] Phase I and II models also differed in grille design, with Phase I units having a narrower grille and Phase II introducing a wider, more rectangular opening.[10] Rare factory variants included GP9s equipped with steam generators for occasional passenger service. Early production runs sometimes omitted dynamic brakes to reduce initial cost, resulting in units without the characteristic rooftop blister and associated equipment, though this option became less common as production progressed.[10]Operators and Service
Original Purchasers
The EMD GP9, a standard 1,750 horsepower four-axle road-switcher, saw widespread adoption by North American railroads seeking to replace steam locomotives with reliable diesel power during the mid-1950s dieselization surge.[1] A total of 4,092 units were produced by Electro-Motive Division for U.S., Canadian, and other operators, while General Motors Diesel produced 646 units primarily for Canadian operators.[1] The model's popularity is evident in the large orders placed by major carriers, reflecting its versatility for freight and yard service across diverse terrains and traffic demands.| Railroad | Quantity | Notes |
|---|---|---|
| Chesapeake & Ohio | 363 | Largest single U.S. order, delivered 1954–1957 for coal and general freight hauls.[16] |
| Illinois Central | 348 | Focused on midwestern mainline operations; built 1954–1959.[1] |
| Union Pacific | 345 | Emphasized western transcontinental routes; included booster units for heavy grades.[1] |
| Canadian National | 434 | GMD-built for CN and subsidiaries (GTW, CV) extensive Canadian network; supplemented earlier GP7s.[17] |
| Southern Pacific | 340 | Allocated to southwestern divisions, including Texas & New Orleans and Cotton Belt subsidiaries.[18] |