MTH: 30-21354-1 - BNSF O Scale RailKing SD-9 Diesel Engine #1722 - w/ Proto-Sound 3.0 - O Gauge - In the General Motors' Electro-Motive Division time line, 1954 holds significance for two important events. In that year, the manufacturer produced its 15,000th locomotive and introduced the 1,750-h.p. SD9. The road switcher was produced until 1959. Basically an elongated — and, some might say, handsomer — version of EMD's very popular GP9, the SD9 spread the same horsepower over two additional axles, resulting in a lower loading on each axle. This made the engine more suitable for use on light rail and in situations requiring power at low speeds, such as hump yard service. - The RailKing Scale model of the SD9 is built to 1/48th scale proportions and is thus somewhat larger than typical RailKing diesels. O gauge operators looking for scale proportioned locomotives will find durable, yet well detailed, RailKing Scale models to be an excellent alternative to more expensive O scale diesels.