EMD SDP45

The EMD SDP45 was a passenger-configured variant of the highly successful SD45 freight locomotive, produced by General Motors' Electro-Motive Division between 1967 and 1970. A total of 52 units were constructed during that period, with the design intended to provide railroads with a high-horsepower locomotive capable of handling both passenger train heating duties and the demanding performance requirements of mainline service. Three railroads ultimately acquired the type, though their operational needs differed considerably from one another. Southern Pacific Railroad was among the first customers, placing an order for ten units in May 1966. These locomotives entered service beginning in mid-1967, initially assigned to the City of San Francisco between Oakland and Ogden. Each unit cost the railroad approximately $317,156, a notable premium over the comparable SD45 freight locomotive of the same era. After Amtrak assumed control of long-distance passenger operations in 1971, some of Southern Pacific's SDP45s were leased to the new national carrier for West Coast service before eventually being redirected to commuter operations on the San Francisco Peninsula beginning in 1973, where they replaced Fairbanks-Morse Train Masters. They remained in that demanding commuter role until 1985, after which they were reassigned to freight work before final retirement between 1986 and 1990. The Great Northern Railway purchased eight SDP45s in 1967 to modernize motive power on the Empire Builder, typically operating them in back-to-back pairs. Following the creation of Burlington Northern Railroad through the 1970 merger, these units were eventually reassigned to freight service alongside six SDP40 locomotives also inherited from Great Northern. The largest single order came from Erie Lackawanna Railroad, which acquired 34 units in 1969 and 1970. Unlike the passenger-oriented examples operated by Southern Pacific and Great Northern, Erie Lackawanna's locomotives were intended exclusively for freight service, and EMD later reclassified these units as SD45Ms to reflect their distinct configuration. Several former Erie Lackawanna SDP45s were subsequently rebuilt by Morrison-Knudsen for Southern Pacific as SD40M-2 locomotives, and it is largely this rebuilt group that accounts for the type's surviving examples. One unit, Erie Lackawanna 3639, later operated as Conrail 6670, has been associated with the Virginia Museum of Transportation, though its preservation status has remained somewhat uncertain over the years.

The SDP45 was powered by the EMD 645E3 prime mover, a 16-cylinder turbocharged diesel engine producing 3,600 horsepower, the same powerplant used in the standard SD45. The locomotive rode on a C-C wheel arrangement with six powered axles, and its DC traction system was conventional for road diesels of the period. The most distinguishing physical feature of the passenger-configured SDP45 was its extended long hood, which was squared off at the rear to accommodate a steam generator for heating passenger cars. Southern Pacific's units used a Vapor Model OK-4740 steam generator and carried approximately 2,500 gallons of fuel along with 3,000 gallons of water for steam generation, both stored in a partitioned underframe tank. Southern Pacific initially ordered its units with 62:15 gearing suited for passenger speeds, later adjusting the ratio before ultimately returning most units to the original gearing for commuter service. The freight-only units delivered to Erie Lackawanna differed visibly from their passenger counterparts, retaining the angled long hood end typical of standard road switchers rather than the squared-off rear hood of the passenger versions. The space that would have housed a steam generator was instead filled with concrete ballast to maintain proper weight distribution, and the longer overall frame made possible by the SDP45's stretched design allowed for a larger fuel tank, extending the operational range of these freight locomotives between refueling stops. One Burlington Northern SDP45 was later used as an experimental platform by EMD in 1983 and 1984, being fitted with an articulated four-axle rear truck in a configuration designated HT-BB, though advances in traction motor technology ultimately rendered the experimental arrangement unnecessary for production application.

Models by: Athearn · Walthers