2-10-4

Under the Whyte notation for the classification of steam locomotives, a 2-10-4 locomotive has two leading wheels in a leading truck, ten driving wheels (in other words, five driven axles), and four trailing wheels in a trailing truck. These were referred to as the "Texas" type in the United States, and the "Selkirk" type in Canada.

The equivalent UIC classification is 1'E2'.

This locomotive type can either be viewed as a 2-10-2 "Santa Fe" type with an enlarged firebox requiring the larger trailing truck, or a longer 2-8-4 "Berkshire" type requiring extra driving wheels to fit within axle-loading limits. Indeed, examples of both of those evolutionary progressions can be found.

Santa Fe prototype

The first 2-10-4 was indeed a 2-10-2 "Santa Fe" type with a bigger trailing truck; in 1919 the Atchison, Topeka & Santa Fe Railroad built one of its 3800 class 2-10-2 locomotives, #3829, with a 4-wheel trailing truck to see if there were any advantages. However, no attempt to expand the locomotive to take advantage of the larger truck was done, and the locomotive remained a one-off, although it carried the 4-wheel truck until its demise in 1955.

Lima revives the 2-10-4

The 2-10-4 type was revived in 1925 by the Lima Locomotive Works, and this time it was an expansion of the 2-8-4 "Berkshire" type that Lima had pioneered. The four-wheel trailing truck allowed a much larger firebox and thus a greater ability to generate heat (and thus steam) - the Superpower design, as Lima's marketing department called it, meant for a locomotive that could develop great power at speed and not run out of steam-generating ability. A version of the Berkshire with ten driving wheels instead of eight was an obvious development, and the first delivered were to the Texas and Pacific Railway, after which the type was named.

The C&O perfects the type

The early Lima Texas types were low-drivered, 60 through 64 inches (152.4 through 162.6 cm) in diameter, which did not give enough space to fully counterweight the extremely heavy and sturdy side rods and main rods required for such a powerful locomotive's piston thrusts. That changed with the Chesapeake & Ohio Railroad in 1930, who stretched an Erie Railroad high-drivered Berkshire type to produce 40 of the T-1, a Texas with 69 inch (175.3 cm) drivers that was both powerful and fast, fast enough for the new higher-speed freight services the railroads were introducing. All subsequent Texas types were of this higher-drivered sort.

The Pennsy's "War Babies"

The Pennsylvania Railroad (PRR) ordered few new locomotives after 1930; electrification both ate up the railroad's resources and provided a supply of excess steam locomotives, soaking up any requirement for new power. It was not until World War II had begun that the PRR's locomotive fleet began to look inadequate. The Pennsy needed new, modern freight power in a hurry. The War Production Board prohibited working on a new design, and in any case there was not enough time to trial a prototype. Instead, the PRR cast around for other railroads' designs it might modify for PRR use, settling on the C&O T-1. Some modifications were made for the PRR; the PRR drop-coupler, sheet steel pilot, a PRR style cab, a large PRR tender, a Keystone numberplate up front, and other modifications. It still betrayed its foreign heritage by lacking the PRR trademark Belpaire firebox and by having a booster engine on the trailing truck. 125 locomotives were built between 1942 and 1944, the largest fleet of Texas type locomotives in existence.

Santa Fe's express locomotives

The Santa Fe, who had originated the 2-10-4 type, tried again in 1930 with #5000, nicknamed "Madam Queen". This locomotive was very similar to the C&O T-1 described above, with the same 69 in (1.75 m) drivers. It proved the viability of the type on the Santa Fe, but the Great Depression shelved plans to acquire more. In 1938, with the railroad's fortunes improving, the Santa Fe did acquire ten locomotives; these were ordered with 74 in (1.88 m) drivers and 310 lbf/in² (2.1 MPa) boiler pressure, making the Santa Fe 2-10-4s the fastest and most modern of all. Of the original order of ten, five were oil-burning and five coal-burning; when the Santa Fe ordered 25 more for 1944 delivery, all were delivered equipped to burn oil.

Railroads that owned Texas types

18 of the B&LE's 2-10-4 locomotives were sold to the Duluth, Missabe & Iron Range. The DMIR kept the "Texas" class name on these locomotives.

Outside North America

Outside North America, the 2-10-4 was rare. The Central Railway of Brazil, however, ordered a narrow gauge (metre gauge) 2-10-4 from Baldwin, which was delivered in 1940. The South African Railways owned 2-10-4s as well, built by the North British Locomotive Works. In addition, some 2-10-4 tank locomotives existed in eastern Europe. One bizarre experimental 2-10-4 built in the Soviet Union had an opposed piston drive system.

External links

• SteamLocomotive.com's page on the Texas type (http://www.steamlocomotive.com/texas/)
• 2-10-4 or Texas (http://www.trains.com/Content/Dynamic/Articles/000/000/001/813octce.asp) (Trains Magazine)

References

• Barris, W., The Texas Type Locomotive (http://www.steamlocomotive.com/texas/). Retrieved January 1 2003
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