4-12-2

Union Pacific #9000.

A 4–12–2, in the Whyte notation for the classification of steam locomotives by wheel arrangement, is a locomotive with four leading wheels in a leading truck, twelve driving wheels (six axles) in a rigid frame, and two trailing wheels in a trailing truck.

Only one type of 4–12–2 was built, the Union Pacific Railroad's 9000 class locomotives, 103 of which were built by ALCO between 1926 and 1930. These locomotives were used to increase the speed of freight trains in flat country, and were fairly successful, but were maintenance nightmares, largely because of their use of an inaccessible third cylinder driving a cranked second driving axle between the frames.

One example survives, at the Railway and Locomotive Historical Society's museum at the Los Angeles County Fairplex at Pomona, California.

Specifications

References

Westcott, Linn H. (1960). Model Railroader Cyclopedia – Volume 1: Steam Locomotives. Kalmbach Books. ISBN 0–89024–001–9.

Steam locomotive types

Single engine types

0–2–2, 2–2–0, 2–2–2, 2–2–4, 4–2–0, 4–2–2, 4–2–4, 6–2–0

0–4–0, 0–4–2, 0–4–4, 2–4–0, 2–4–2, 2–4–4, 4–4–0, 4–4–2, 4–4–4

0–6–0, 0–6–2, 0–6–4, 2–6–0, 2–6–2, 2–6–4, 4–6–0, 4–6–2, 4–6–4

0–8–0, 0–8–2, 2–8–0, 2–8–2, 2–8–4, 4–8–0, 4–8–2, 4–8–4, 6–8–6

0–10–0, 0–10–2, 2–10–0, 2–10–2, 2–10–4, 4–10–0, 4–10–2

0–12–0, 2–12–2, 4–12–2

Duplex engine types

4–4–4–4, 6–4–4–6, 4–4–6–4, 4–6–4–4

Mallet (articulated) types

0–4–4–0, 2–4–4–2

0–6–6–0, 2–6–6–2, 2–6–6–4, 2–6–6–6, 4–6–6–4

0–8–8–0, 2–8–8–0, 2–8–8–2, 2–8–8–4, 4–8–8–2, 4–8–8–4

2–10–10–2, 2–8–8–8–2, 2–8–8–8–4