In
Whyte notation, a '0-4-2' is a
railroad steam locomotive that has four coupled
driving wheels followed by two
trailing wheels, with no
leading wheels. 0-4-2 locomotives are typically tank engines, which is noted by adding a T to the end, 0-4-2T.
The equivalent
UIC classification is 'B1’'.
New Zealand
The 0-4-2T arrangement was used by two
classes of locomotives operated by the
New Zealand Railways Department. The first was the
C class of 1873, originally built as
0-4-0T. The class was found to be unstable at speeds higher than 15 mph, so by 1880, all members of the class had been converted to 0-4-2T to rectify this problem. The second and more notable 0-4-2T class, and the only one actually built as 0-4-2T, was the unique
H class designed to operate the
Rimutaka Incline on the
Wairarapa Line. The Incline's steep gradient necessitated the use of the
Fell mountain railway system, and the six members of the H class spent their entire lives operating trains on the Incline. Except for a few brief experiments with other classes, the H class had exclusive use of the Incline from their introduction in 1875 until the Incline's closure in 1955. The class leader, H 199, is preserved on static display at the
Fell Engine Museum in
Featherston and is the only extant Fell locomotive in the world.
0-4-2T was also employed for steam locomotives operated by small private industrial railways and
bush and mineral tramways. One such locomotive, built by
Peckett and Sons in 1938, is currently operational on the
Goldfields Railway that runs between
Waihi and
Waikino along a stretch of the former route of the
East Coast Main Trunk Railway in the
Bay of Plenty.
See also

LMR 57 Lion, the second oldest operable steam locomotive in the world
★
LMR 57 Lion
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LB&SCR B1 Class