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"; production ceased in January 1986. The SD50 was a transitional model between EMD's Dash 2 series which was produced throughout the 1970s and the

microprocessor A microprocessor is a computer processor (computing), processor for which the data processing logic and control is included on a single integrated circuit (IC), or a small number of ICs. The microprocessor contains the arithmetic, logic, a ...

-equipped SD60 and SD70 locomotives. A total of 431 were built.

History

The SD50 was produced in response to increasingly tough competition from

GE Transportation GE Transportation is a division of Wabtec. It was known as GE Rail and owned by General Electric until sold to Wabtec on February 25, 2019. The organization manufactures equipment for the railroad, marine, mining, drilling and energy generatio ...

, 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. The GM-EMD locomotives that immediately preceded the SD50, the SD45 and SD45-2, used huge, 20-cylinder engines that consumed large amounts of fuel and suffered from reliability problems when first introduced. Demand for the 45 series dropped sharply after the 1970s fuel crisis. The SD50 used an updated version of the V16 645 from the SD40-2, uprated to at 950

rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to hertz. Standards ISO 80000-3:2019 def ...

from at 900 rpm, and uprated again in November 1984 to . This proved to be a step too far; the 50 series models were plagued by engine and electrical system problems which harmed EMD's sales and reputation. Compared with their predecessors, the SD50 had a longer frame and a substantially longer long hood. In addition, the resistors for the dynamic brake grid were moved from their location on previous models above the

prime mover Prime mover may refer to: Philosophy *Unmoved mover, a concept in Aristotle's writings Engineering * Prime mover (engine or motor), a machine that converts various other forms of energy (chemical, electrical, fluid pressure/flow, etc.) into ener ...

to a new, cooler location in front of the engine compartment air intakes, closer to the electrical switchgear. This increased their separation from other systems, simplifying maintenance for the prime mover and the electrical system. One former SD50 engineer praised the locomotives' wheel-slip control system and dynamic braking power, stating "they were able to give more adhesion than a SD40-2".

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 An alternator (or synchronous generator) is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field wit ...

. The power generated by the traction alternator drove 6 EMD D87 traction motors rated at 1170 amps each. The SD50 was available with multiple traction motor gearing ratios and wheel sizes, the most common of which was the 70:17 ratio with wheels, which allowed for a top speed of . Other gearing options for the SD50 with wheels included 69:18 for , 67:19 for and 66:20 for . The SD50 was also available with wheels. The SD50 was also available with either HT-C trucks (identified with a hydraulic shock on the side of the middle axle of each truck) or the earlier Flexicoil trucks. Some investigators implicated the HT-C truck in derailments of

Amtrak The National Railroad Passenger Corporation, Trade name, doing business as Amtrak (; ), is the national Passenger train, passenger railroad company of the United States. It operates intercity rail service in 46 of the 48 contiguous United Stat ...

's SDP40Fs, so

Conrail Conrail , formally the Consolidated Rail Corporation, was the primary Class I railroad in the Northeastern United States between 1976 and 1999. The trade name Conrail is a portmanteau based on the company's legal name. It continues to do busine ...

chose the Flexicoil C trucks for their SD40-2s and their first order of SD50s—the only customer to do so. The controversy surrounding the HT-C truck was eventually disproved, and Conrail chose HT-C trucks for their second order of SD50s and SD60s.

SD50S

The SD50S ("short frame") were prototype units built in December 1980. They were shorter than production locomotives by approximately . There were six SD50Ss built, all of which were sold to the Norfolk & Western and eventually passed to

Norfolk Southern The Norfolk Southern Railway is a Class I freight railroad operating in the Eastern United States. Headquartered in Atlanta, the company was formed in 1982 with the merger of the Norfolk and Western Railway and Southern Railway. The comp ...

. They were withdrawn in the early 2000s as non-standard. Two were rebuilt in 2008 as "SD40E" models by Norfolk Southern's

Juniata Shops Altoona Works (also known as Altoona Terminal) is a large railroad industrial complex in Altoona, Pennsylvania. It was built between 1850 and 1925 by the Pennsylvania Railroad (PRR), to supply the railroad with locomotives, railroad cars and re ...

, along with several standard length SD50s. NS Loco No

The SD50S designation was also used for five locomotives built by EMD Australian licensee Clyde Engineering,

Adelaide Adelaide ( , ; ) is the list of Australian capital cities, capital and most populous city of South Australia, as well as the list of cities in Australia by population, fifth-most populous city in Australia. The name "Adelaide" may refer to ei ...

for Hamersley Iron. Shorter than production SD50s, they were equipped with a special double cab roof for insulation against the hot Australian desert sun in the

Pilbara The Pilbara () is a large, dry, sparsely populated regions of Western Australia, region in the north of Western Australia. It is known for its Indigenous Australians, Aboriginal people; wealth disparity; its ancient landscapes; the prevailing r ...

region. Withdrawn in November 1995, they were sold to National Railway Equipment Company and exported to the United States in February 1999 and used in national lease service. They were subsequently sold to the Utah Railway in June 2001. In June 2017, 6063 and 6064 were sold to the Chicago, Fort Wayne & Eastern Railroad, 6064 was relocated by

Genesee & Wyoming Genesee & Wyoming Inc. (G&W) is an American short line railroad holding company, that owns or maintains an interest in 122 railroads in the United States, Canada, Belgium, Netherlands, Poland, and the United Kingdom; and formerly in Australia. ...

to the Indiana & Ohio Railway and renumbered 5016 and 5017.Motive Power Roundup '' Motive Power'' issue 119 September 2018 page 104

SD50F

The SD50F was a Canadian

cowl unit A cowl is an item of clothing consisting of a long, hooded garment with wide sleeves, often worn by monks. It was developed during the Early Middle Ages. The term may have originally referred to the hooded portion of a cloak, though contemporar ...

version equipped with a "Draper taper" (inset section aft of cab for limited rear visibility). Sixty were built for the

Canadian National Railway The Canadian National Railway Company () is a Canadian Class I freight railway headquartered in Montreal, Quebec, which serves Canada and the Midwestern and Southern United States. CN is Canada's largest railway, in terms of both revenue a ...

as road numbers 5400–5459. Early engine problems resulted in a temporary down-rating to . Eventually the units were re-rated to ; however, like their U.S. cousins, they continued to suffer from relatively low reliability, frequently suffering engine, power assembly, and crankshaft failures.

Original owners

Rebuilds

A number of SD50s have been rebuilt into the equivalent of SD40-2s. The ''Dash 2'' features are already contained within the SD50. The units are derated from at 950 rpm to at 900 rpm. This is actually a quite simple change to the locomotive's Woodward PGE engine governor.

Preservation

• In late October 2022, the Illinois Railway Museum acquired former CNW 7009, believed by the museum to be the first preserved SD50.

References

External links

* Lytle, Stan.
EMD SD50 list
'. Retrieved 16 February 2005. * TrainWeb.com.

'. Retrieved 7 January 2005. Contains fairly complete builders' records for EMD production. * * {{CN Cowls C-C locomotives Clyde Engineering locomotives Diesel–electric locomotives of the United States Diesel locomotives of Western Australia SD50 Freight locomotives SD50 Railway locomotives introduced in 1980 Standard-gauge locomotives of the United States Standard-gauge locomotives of Canada Standard-gauge locomotives of Australia Diesel–electric locomotives of Australia Baltimore and Ohio locomotives Canadian National Railway locomotives Chesapeake and Ohio locomotives Chicago and North Western Railway locomotives Conrail locomotives Denver and Rio Grande Western Railroad locomotives Norfolk Southern Railway locomotives