| EMD SD50 | |
|---|---|
| Power type | Diesel-electric |
| Builder | GM Electro-Motive Division (EMD) General Motors Diesel (GMD) |
| Build date | December 1980 – July 1987 |
| Total produced | 427 |
| Gauge | 4 ft 8 1⁄2 in (1,435 mm) |
| Prime mover | EMD 16-645-F3B |
| Alternator | main : AR11 |
| Power output | 3,500 hp (2,610 kW) |
| Disposition | Many in service, many sold to regionals, dealers, or leasing companies as of 2008 |
The EMD SD50 was a 3,500-horsepower (2,610 kW) 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.
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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 3,600 hp (2,680 kW) 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 3,600 hp (2,700 kW) 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 3,500 hp (2,600 kW) from 3,000 hp (2,240 kW). This proved to be a step too far; the 50 series models were plagued by engine problems which harmed both sales and the reputation of EMD.
The subsequent SD60 model replaced the overstressed 645 engine with a new engine series, the 710.
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.
The SD50 is powered by V16 16-645F3 series diesel engine driving either an EMD AR11A-D14 or an EMD AR16A-D18 main alternator. The power generated by the main 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 40-inch (1,000 mm) wheels, this allowed for a top speed of 70 mph (110 km/h). Other gearing options for the SD50 with 40-inch (1,000 mm) wheels include 69:18 for 76 mph (122 km/h), 67:19 for 82 mph (132 km/h) and 66:20 for 88 mph (142 km/h). 42 inch 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 older Flexicoil trucks, which only Conrail opted for. Some investigators had linked the HT-C truck to derailments in Amtrak's SDP40F locomotive fleet and Conrail chose to order SD40-2's and their first order of SD50's with the older Flexicoil C truck. The controversy surrounding the HT-C truck was largely disproven, and Conrail's second order of SD50's as well as their SD60 variants were all HT-C equipped.
The SD50 could be equipped with fuel tanks sizes from 3,200 US gallons (12,100 l) up to 4,400 US gallons (16,700 l), had a lube oil capacity of 396 US gallons (1,500 l) and a cooling water capacity of 276 US gallons (1,040 l).
The SD50S ("short frame") were prototype units built in December 1980. They were shorter than production locomotives by approximately 2 feet (0.61 m). All of these prototypes were sold to the Norfolk & Western and passed to the Norfolk Southern; they were withdrawn in the early 2000s as non-standard. Two were rebuilt in 2008 as "SD40E" models by Norfolk Southern's Juniata Shops, along with several standard length SD50's.
The designation also applies to five locomotives built by EMD Australian licensee Clyde Engineering for Hamersley Iron. These were also shorter than production SD50s, and were equipped with a special double cab roof for insulation against the hot Australian desert sun. When withdrawn from Hamersley Iron service, they were sold to National Railway Equipment Company and exported to the U.S. in February 1999 and used in national lease service. They were subsequently sold to the Utah Railway in June 2001, where they remain.
The SD50F was a Canadian cowl unit version equipped with a "Draper taper" (inset section aft of cab for limited rear visibility). 60 were built for the Canadian National Railway as road numbers 5400-5459. Early engine problems resulted in a temporary down-rating to 3,300 horsepower (2,500 kW). Eventually the units were re-rated to 3,500 horsepower (2,600 kW), however they, like their U.S. cousins, continued to suffer from relatively low reliability, frequently suffering engine, power assembly, and crankshaft failures.
| Owner | Quantity | Numbers | Notes |
|---|---|---|---|
| Baltimore and Ohio Railroad | 20 | 8576-8595 | to CSX Transportation, most have been rebuilt into SD50-2's. 14 rebuilt into SD50-3's. |
| Canadian National Railway | 60 | 5400-5459 | SD50F, retired, sold or scrapped |
| Chicago and North Western Railway | 35 | 7000-7034 | to Union Pacific, retired |
| Chesapeake and Ohio Railway | 43 | 8553-8575, 8624-8643 | to CSX Transportation, most have been rebuilt into SD50-2's. 14 rebuilt into SD50-3's. |
| Conrail | 135 | 6700-6834 | to CSX Transportation, Norfolk Southern Railway and Kansas City Southern, CSX-inherited units have been rebuilt into SD50-2's. 1 rebuilt to SD50-3 specs. |
| Denver and Rio Grande Western Railroad | 17 | 5501-5517 | to Southern Pacific, to Union Pacific, retired |
| Kansas City Southern Railway | 10 | 703-713 | |
| Missouri Pacific Railroad | 60 | 5000-5059 | to Union Pacific, retired |
| Norfolk and Western Railway | 6 | 6500-6505 | SD50S short frame to Norfolk Southern Railway |
| Seaboard System Railroad | 81 | 8500-8552, 8596-8623 | to CSX Transportation, most have been rebuilt into SD50-2's. 14 rebuilt into SD50-3's. |
| Southern Railway | 20 | 6506-6525 | to Norfolk Southern Railway |
As of 2008, current owners and operators include:
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