4-4-2 (locomotive)
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Pennsylvania Railroad E6s.

A 15 in gauge 4-4-2 operating on the Riverside and Great Northern Railway in Wisconsin Dells, WI.

A 4-4-2 inspection locomotive.

In the Whyte notation a 4-4-2 is a steam locomotive that has a two-axle leading truck, two powered driving axles and a one-axle trailing truck. This locomotive wheel arrangement is commonly called an Atlantic type.

Other equivalent classifications are:
UIC classification: 2B1 (also known as German classification and Italian classification)
French classification: 221
Turkish classification: 25
Swiss classification: 2/5

History

Atlantics were built expressly for passenger service in the evolvement from the unstable mainline express 2-4-2. A number of railroads had moderate fleets of 4-4-2s for use in express, local and commute service. One of the best-known groups of 4-4-2s (among such as the Milwaukee Road Hiawatha engines) in the United States was the Pennsylvania Railroad's vast fleet of E class Atlantics culminating in the E6s class. In the United Kingdom one of the best-known series was the 'Great Northern Atlantic' fleet, incorporated into the fleet of the London and North Eastern Railway at the inter-war grouping of companies.

The original Atlantics were built with hauling wood-frame passenger cars in mind, and came in a variety of configurations, including the four-cylinder Vulcain Compound which had previously been used on express 4-4-0s, 4-6-0s and 2-4-2s. Around the 1910s though, American railroads started buying steel passenger cars, which precipitated the introduction of the 4-6-2 Pacific type as the standard passenger engine, which had previously been a mountain engine. Nonetheless, The Chicago and North Western, Southern Pacific, Pennsylvania Railroad, and the Santa Fe railways used 4-4-2s until the bitter end of steam locomotive fleets in the 1950s, some even being carefully used in light local freight switching service.

For modern use, Atlantics were ill-suited for mountain or for very-long-distance operations. 4-4-2s had high-diameter driving wheels; in some cases exceeding 6 feet (1.8 m) which were adequate for 70 to 100 mph (113 to 161 km/h) trains, although they tended to "chop" on higher speeds. Climbing any railroad grade required a lower drive wheel diameter for adhesion or more drive wheels for traction, although prior to world war one, they were used as mountain helpers.

Hiawatha service

One of the Milwaukee Road's streamlined 4-4-2s.

The Milwaukee Road used the Atlantic type on its midwestern Hiawatha passenger trains; four (4-4-2) locomotives of class A were constructed in 1935. Reid wrote these 4-4-2s were 'the first steam locomotives ever designed and built to reach 100 mph (160 km/h) every day.'¹ The engines developed 30,685 lbf (136,490 N) of tractive effort. An unusual feature of this locomotive, was the drive onto the front coupled axle, which 'improved riding qualities.'² The railroad's Atlantics, in their distinctive streamline shrouds, were designed by industrial designer Otto Kuhler. All of the locomotives were eventually withdrawn between 1949–1951, then scrapped and none survive.

Swengel wrote the engines were 'beautifully cross balanced' and ran on 84-inch (2.1 m) drivers, had an oil fired 69-square-foot (6.4 m²) grate and a boiler pressure of 300 psi, which gave the boiler a high capacity relative to the cylinders. They were designed, said Swengel, for a light-weight train of 5-6 cars. They were, he claimed, 'probably the fastest steam locomotives ever built in America, and possibly were capable of matching any locomotive in the World.' The fleet ran their 431-mile (694 km) schedule in 400 minutes, with several stops en route, averaging in parts over 100 miles per hour and often stopped with 'one or two minutes to spare'.

Survivors

As a result of these engines being superseded by more modern steam traction, few have survived.

In the UK

• Great Northern Railway, 990, Henry Oakley. National Collection. Now static at Bressingham Steam & Gardens.
• Great Northern Railway, 251. National Collection. First large-boilered Great Northern Railway Atlantic.
• The Bluebell Railway is building a replica of a LB&SCR Atlantic, similar to the GNR large boilered Atlantics.
• The Great Western Society is working on a replica of a 4-6-0 'Saint' class locomotive. Some of these ran as Atlantics for comparative purposes and the replica will run as an Atlantic from time to time.

In the USA

• Southern Pacific, 3025. Travel Town Museum, Los Angeles, CA.
• Chicago & North Western, 1015. Museum of Transportation, St. Louis, MO.
• Pennsylvania Railroad E6s 460. Railroad Museum of Pennsylvania, Strasburg, PA.
• Pennsylvania Railroad, 7002 (formerly 8063) Railroad Museum of Pennsylvania, Strasburg, PA. Has steamed since preservation, now static.

References

• Reed, Brian (1972). "The Hiawathas". Loco Profile (Windsor: Profile Publications) (No. 26). 
• SteamLocomotive.com
• Swengel,F. M. (1967). The American Steam Locomotive, Vol. 1. Evolution of the Steam Locomotive. Davenport, Iowa: MidWest Publications, pp. 260-261. 

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