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Diagram of the 2-10-2 Wheel Arrangement: one small leading wheel, five large driving wheels joined together with a coupling rod, and one small trailing wheel.

2-10-2 Santa Fe Steam Locomotive
Under the Whyte notation for the classification of steam locomotives, 2-10-2 represents the wheel arrangement of two leading wheels on one axle, usually in a leading truck, ten powered and coupled driving wheels on five axles, and two trailing wheels on one axle, usually in a trailing truck. In the United States of America and elsewhere the 2-10-2 is known as the Santa Fe type, after the Atchison, Topeka and Santa Fe Railway that first used the type in 1903.

The 2-10-2 wheel arrangement evolved in the United States from the 2-10-0 Decapod of the Atchison, Topeka and Santa Fe Railway (ATSF). Their existing 2-10-0 locomotives, used as pushers up Raton Pass, encountered problems reversing back down the grade for their next assignments since they were unable to track around curves at speed in reverse and had to run very slowly to avoid derailing. Consequently, the ATSF added a trailing truck to the locomotives which allowed them to operate successfully in both directions. These first 2-10-2 locomotives became the forerunners to the entire 2-10-2 family.

The trailing truck allows a larger, deeper firebox than that of a 2-10-0. Like all ten-coupled designs, the long rigid wheelbase of the coupled wheels presented a problem on curves, requiring flangeless drivers, lateral motion devices and much sideplay on the outer axles. To limit this problem, the coupled wheels were generally small, up to 64 inches (1,630 mm) in diameter, which in turn generated the problem of insufficient counterweights to balance the weight of the driving rods.

The 2-10-2's inherent problem was the low speed restriction on the type, which was about 35 miles per hour (56 kmph). Further, the 2-10-2 had other inherent restrictions. The massive cylinders that were required on locomotives in the United States for high tractive effort had the result that no reasonably sized valves could admit and exhaust steam at a sufficient rate to permit fast running. In addition the 2-10-2, like the 2-6-2, had its main rod connected to the middle coupled axle, very near to the center of gravity, which created a violent nosing action when operating at speed. The peak of the 2-10-2 design limitations was reached in the United States in 1926 and was overcome with the advent of the superior 2-10-4 design.

Usage

Locomotives with a 2-10-2 wheel arrangement were used in a number of countries around the world, including those in North America, Western Europe, China, the Soviet Union and Africa. Continental Europe saw a fair number of 2-10-2s, although the type was always less popular than 2-8-2 Mikados and 2-10-0 Decapods. A large number of European 2-10-2s were tank locomotives, taking advantage of the symmetrical nature of the wheel arrangement.

United States
In the United States, the 2-10-2 type was produced between 1903 and 1930. The first were the Atchison, Topeka and Santa Fe Railway (AT&SF) engines of the 900 and 1600 series, which were an early type with few advantages over the 2-10-0 Decapod, save their ability to operate in reverse without derailing. By 1919, the AT&SF was building the definitive type, with the trailing truck supporting a large firebox. These were of the AT&SF 3800 class. One of them, AT&SF engine no. 3829, was equipped with an experimental two-axle trailing truck to become the first 2-10-4 Texas type.

About 2,200 Santa Fe types were built, including about 500 of the two United States Railroad Administration (USRA) First World War standard designs. There were two USRA standard 2-10-2s, the heavy version with an engine weight of 380,000 pounds (172,365 kg) and the light version with an engine weight of 352,000 pounds (159,665 kg). The Santa Fe had the most with 352 engines.

The heaviest 2-10-2s were ten locomotives built by Baldwin Locomotive Works for the Reading Railway c. 1931, weighing 451,000 pounds (204,570 kg), engine only.

At 104,000 pounds-force (460 kn), the Illinois Central Railroad’s 2800 class rebuilds probably had the highest calculated tractive effort of any two-cylinder steam locomotive, although the adhesive weight was only 333,000 pounds (151,050 kg).

The Baltimore and Ohio Railroad ordered its first 2-10-2 from Baldwin in 1914. From 1914 to 1956, their 2-10-2s bore numbers commencing with 6, hence the nickname Big Sixes. Designated the S class, there were several sub-classes. They began to be withdrawn in 1951 and were all scrapped by 1959.

Canada
In 1916, Canadian National Railways (CNR) took delivery of ten Class T-1-a 2-10-2's from an order made by the short-lived Canadian Government Railways and built by ALCO. Ten more were delivered from the Montreal Locomotive Works in 1918, and another 25 slightly modified T-1-c's in 1920 that were 1,100 pounds lighter. Canadian Locomotive Company produced five T-2-a's in 1924. Ten ALCO's named T-3-a's were acquired from the Boston and Albany Railroad in 1928. Canadian Locomotive Company produced the last series of 2-10-2's for CNR, a batch of 15 T-4-a's in 1929, and 18 T-4-b's in 1930.The 2-10-2's began to be scrapped in the mid-1950s, with the last models being used until 1961. There are two surviving CNR 2-10-2 locomotives. One is no. 4008 on display at the CNR Station in Rainy River, ON and the other is no. 4100 on display at the Canadian Railway Museum in Delson, QC.

2-10-2 Santa Fe Overview
Equivalent classifications
UIC class: 1E1
French class: 151
Turkish class: 57
Swiss class: 5/7
Russian class: 1-5-1
First known tank engine version
First use: 1922
Country: Germany
Locomotive: Prussian T 20
Railway: Deutsche Reichsbahn
Designer: Prussian state railways
Builder: Borsig & Hanomag
First known tender engine version
First use: 1903
Country: United States
Locomotive: AT&SF 900 class
Railroad: Atchison, Topeka and Santa Fe
Builder: Atchison, Topeka and Santa Fe
Evolved from: 2-10-0
First known "True type" version
First use: 1919
Country: United States
Locomotive: AT&SF 3800 class
Railroad: Atchison, Topeka and Santa Fe
Builder: Atchison, Topeka and Santa Fe
Evolved to: 2-10-4
Benefits: Larger and deeper firebox
Drawbacks: Nosing action at speed

See also:

Steam Locomotives

Reading 2-10-2 No. 3000.

Snake River Farms Wagyu Brisket

A 2-10-2 Slideshow.

Diagram of the 2-10-2 Wheel Arrangement:  one small leading wheel, five large driving wheels joined together with a coupling rod, and one small trailing wheel.

Reading 2-10-2 No. 3000.
Santa Fe herald.
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