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The EMD SD50 is a diesel-electric locomotive built by General Motors Electro-Motive Division. It was introduced in May 1981 as part of EMD's "50 Series", but prototype SD50S locomotives were built from 1980; production ceased in January 1986. The SD50 was in many respects a transitional model between EMD's Dash 2 series which was produced throughout the 1970s and the microprocessor-equipped SD60 and SD70 locomotives. ==History== The SD50 was produced in response to increasingly tough competition from GE Transportation Systems, whose Dash 7 line was proving quite successful with railroads. While EMD's SD40-2 was a reliable and trusted product, GE's line included locomotives up to with more modern technology, as well as very competitive finance and maintenance deals. EMD responded throughout the SD50 program by offering discounts on large orders, this was also a response to the slow U.S. economy in the 1980s which cut locomotive orders. GM-EMD had previously produced locomotives, the SD45 and later SD45-2, but these used huge, 20-cylinder engines with high fuel consumption, and had reliability problems when first introduced. Demand for the 45 series dropped sharply after the 1970s fuel crises. The SD50 used an updated version of the V16 645 used in the SD40-2, uprated to - and later - at 950 rpm from at 900 rpm. This proved to be a step too far; the 50 series models were plagued by engine and electrical system problems which harmed both sales and the reputation of EMD. The subsequent SD60 model replaced the overstressed 950 rpm 645F engine with a new engine series, the 900 rpm 710G. The SD50's long hood saw changes from previous EMD models. The overall frame length was increased, and the long hood was made substantially longer. The resistors for the dynamic brake grid were moved from their previous location above the prime mover to a new, cooler location in front of the engine compartment air intakes, where they were more effectively separated from the rest of the locomotives' systems, and also closer to the locomotive's electrical switchgear, thereby simplifying the prime mover maintenance procedures, and the electrical system as well. ==Technical== The SD50 is powered by V16 16-645F3 series diesel engine driving either an EMD AR11A-D14 or an EMD AR16A-D18 traction alternator. The power generated by the traction alternator drove 6 EMD D87 traction motors rated at 1170 amps each. Depending on customer options, the SD50 was available with a multitude of traction-motor gearing ratio and wheel size options, the most common of which being the 70:17 ratio with wheels, this allowed for a top speed of . Other gearing options for the SD50 with wheels include 69:18 for , 67:19 for and 66:20 for . wheels were also available. Customers of the SD50 also had the option of either HT-C trucks (identified with a hydraulic shock on the side of the middle axle of each truck) or the earlier Flexicoil trucks, which only Conrail opted for. Some investigators implicated the HT-C truck in derailments in Amtrak's SDP40F locomotive fleet and Conrail chose to order SD40-2s and their first order of SD50s with the earlier Flexicoil C truck. The controversy surrounding the HT-C truck was eventually disproved, and Conrail's second order of SD50s as well as their SD60 variants were all HT-C equipped. The SD50 could be equipped with fuel tanks sizes from up to , had a lube oil capacity of and a cooling water capacity of . 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「EMD SD50」の詳細全文を読む スポンサード リンク
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