"Superpower steam" was a term coined by

Lima Locomotive Works Lima Locomotive Works was an American firm that manufactured railroad locomotives from the 1870s through the 1950s. The company took the most distinctive part of its name from its main shop's location in Lima, Ohio. The shops were located between ...

in the mid-1920s, referring to steam locomotives with

booster Booster may refer to: Amusement rides * Booster (Fabbri ride), a pendulum ride * Booster (HUSS ride), an evolution of the Breakdance ride * Booster (KMG ride), a pendulum ride Arts, entertainment, and media Fictional characters * Booster, a cha ...

-equipped four-wheel trailing trucks supporting large fireboxes, as well as enlarged

superheater A superheater is a device used to convert saturated steam or wet steam into superheated steam or dry steam. Superheated steam is used in steam turbines for electricity generation, steam engines, and in processes such as steam reforming. There ar ...

s. The wheel arrangements introduced in the 1920s for these locomotives were the

4-6-4 Under the Whyte notation for the classification of locomotives, represents the wheel arrangement of four leading wheels, six powered and coupled driving wheels and four trailing wheels. In France where the type was first used, it is known as t ...

's,

2-8-4 Under the Whyte notation, a 2-8-4 is a steam locomotive that has two unpowered leading wheels, followed by eight coupled and powered driving wheels, and four trailing wheels. This locomotive type is most often referred to as a Berkshire, though ...

's,

4-8-4 Under the Whyte notation for the classification of steam locomotives, represents the wheel arrangement of four leading wheels on two axles, eight powered and coupled driving wheels on four axles and four trailing wheels on two axles. The type w ...

's and

2-10-4 Under the Whyte notation for the classification of steam locomotives, a locomotive has two leading wheels on one axle, usually in a Bissel truck, ten coupled driving wheels on five axles, and four trailing wheels on two axles, usually in a bogie ...

's; and in the 1930s, the 2-6-6-4's. The term "superpower" was later often applied to all locomotives with 4-wheel trailing truck arrangements, though many did not have boosters and almost all steam of any wheel arrangement built after that time had large superheaters. The design was invented by Lima for the

New York Central The New York Central Railroad was a railroad primarily operating in the Great Lakes and Mid-Atlantic regions of the United States. The railroad primarily connected greater New York and Boston in the east with Chicago and St. Louis in the Midw ...

Boston and Albany Railroad The Boston and Albany Railroad was a railroad connecting Boston, Massachusetts to Albany, New York, later becoming part of the New York Central Railroad system, Conrail, and CSX Transportation. The line is currently used by CSX for freight. Pass ...

. The design was invented by Lima's Vice President of Engineering, William Woodard, who had experimented with a

2-8-2 Under the Whyte notation for the classification of steam locomotives, represents the wheel arrangement of two leading wheels on one axle, usually in a leading truck, eight powered and coupled driving wheels on four axles and two trailing wheel ...

Mikado in 1922. The new design called for double the firebox size than the earlier Mikados, thus giving it more grate area leading to the development of the

. The larger grate area meant that the locomotive could achieve greater steaming capacity, higher speeds, more horsepower, and greater tractive effort. To accommodate the larger firebox, Woodard gave the new locomotive a two axle trailing truck instead of the common single axle trailing trucks previously used, and tests of the new design were done on the

. The design was a smashing success and soon both the

Baldwin Locomotive Works The Baldwin Locomotive Works (BLW) was an American manufacturer of railroad locomotives from 1825 to 1951. Originally located in Philadelphia, it moved to nearby Eddystone, Pennsylvania, in the early 20th century. The company was for decades t ...

and the

American Locomotive Company The American Locomotive Company (often shortened to ALCO, ALCo or Alco) was an American manufacturer of locomotives, diesel generators, steel, and tanks that operated from 1901 to 1969. The company was formed by the merger of seven smaller locomo ...

followed suit.American Steam Locomotive Solomon, Brian MBI Publishing

References

Steam locomotive technologies {{Rail-transport-stub