4-4-2 (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.

The equivalent UIC classification is 2'B1'.

History

Atlantics were built expressly for passenger service. A number of railroads had extensive fleets of 4-4-2s for use in express, local and commute service. One of the best-known groups of 4-4-2s (after the Hiawatha engines) was the Pennsylvania Railroad's vast fleet of E class Atlantics culminating in the E6s class.

Atlantics were built with hauling wood-frame passenger cars in mind. Around the 1910s though, American railroads started buying steel passenger cars, which precipitated the introduction of the 4-6-2 Pacific type. Nonetheless, The Chicago and North Western, Southern Pacific and the Santa Fe railways used 4-4-2s until the bitter end of steam locomotive fleets in the 1950s.

Atlantics were ill-suited for mountain or very-long-distance operations. 4-4-2s had high-diameter driving wheels; in some cases exceeding 6 feet (1.8 m) which were perfect for 70 to 100 mph (113 to 161 km/h) runs. Climbing any railroad grade required a lower driver diameter or more drivers.

Hiawatha service

The Milwaukee Road made extensive use of the Atlantic type on its midwestern Hiawatha passenger trains; 4 locomotives of class A were constructed in 1935. One locomotive hauled as many as 10 passenger cars at speeds up to 100 mph.^{[citation needed]} The railroad's Atlantics in their distinctive streamline shouds, were designed by industrial designer Otto Kuhler.

Swengel wrote the engines were ' beautifully cross balanced' and ran on 84 inch drivers, had an oil fired 69 square foot grate and a boiler pressure of 300 p.s.i., 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 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'.

References

• Swengel,F. M. (1967). The American Steam Locomotive, Vol. 1. Evolution of the Steam Locomotive. Davenport, Iowa: MidWest Publications, pp. 260-261. 

fr:Atlantic (locomotive)

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