GE U25C

The General Electric U25C had its origins in an unusual circumstance: a construction railroad project in northern California. Oro Dam Constructors needed diesel power for a short but demanding heavy-haul operation supporting construction of Oroville Dam, and a GE sales representative offered them what amounted to a six-axle version of the existing U25B road switcher. When that proposal made its way back to GE's manufacturing facility in Erie, Pennsylvania, engineers discovered that no such model existed in their domestic catalog, and company policy had generally been to hold off on a six-axle road switcher until the 3,000-horsepower threshold could be reached. Rather than forfeit the sale, GE moved quickly to develop the U25C, drawing heavily on U25B engineering. The finished design was longer than its four-axle counterpart by approximately four feet and four inches, the additional length necessary to house the improved Trimount trucks. The first units were completed in September 1963, making the U25C the first six-axle second-generation diesel locomotive built for the domestic American market. Production continued through December 1965, with 113 units completed in total. Early customers beyond Oro Dam Constructors included the Atlantic Coast Line, which took delivery of its first four U25Cs in December 1963 alongside an order for Alco C628s, making ACL a notable early adopter of high-horsepower six-axle power from multiple builders. Other purchasers included the Northern Pacific, Lake Superior and Ishpeming, and the Pennsylvania Railroad. As the horsepower race of the mid-1960s intensified, GE responded by producing ten uprated examples for existing U25C customers. Northern Pacific received three units rated at 2,750 horsepower in mid-1965, while Atlantic Coast Line and the Pennsylvania Railroad each received uprated examples at 2,800 horsepower late that same year. Several additional Pennsylvania Railroad units were subsequently uprated to 2,800 horsepower as well. The U25C was succeeded in production by the U28C beginning in early 1966, and the two models shared enough in common that the Phase III carbody used on late U25C production carried over directly into early U28C manufacture. Of the 113 U25Cs built, only one is known to survive: Lake Superior and Ishpeming number 2501, preserved on display in Marquette, Michigan.

The U25C was a diesel-electric locomotive powered by GE's FDL16 prime mover, a sixteen-cylinder version of the FDL engine family, producing 2,500 horsepower in standard configuration. The locomotive rode on a C-C wheel arrangement, meaning two three-axle powered trucks, with all six axles driven by DC traction motors. Production units went through three recognized phases distinguished primarily by fuel tank capacity and carbody ventilation arrangements. Phase I units, built from September 1963 through May 1964, carried a 2,900-gallon fuel tank with air tanks mounted at the ends of the tank and louvers on the equipment boxes beneath the cab on the engineer's side. Phase II units, produced from May through November 1964, featured a larger 3,500-gallon fuel tank and relocated air tanks moved inside the carbody behind the cab, with louvers added to the long hood for ventilation. Phase III units, which accounted for the majority of production, introduced screened panel openings in the carbody in place of the earlier louver arrangements, along with a rectangular roof opening for fresh air intake to cool the air tanks. Certain Phase III locomotives built for the Pennsylvania Railroad and the Louisville and Nashville carried additional equipment boxes and a third handrail stanchion to house extended-range dynamic brake contactors. Late Phase III production saw further refinement, with screened doors replacing screen panels on the engineer's side and the elimination of remaining louvers in that area. The carbody design proved sufficiently adaptable that it was carried forward into the early production run of the U28C without significant alteration.