Editing 4-6-2 (section)

==Overview==
The introduction of the {{nowrap|4-6-2}} design in 1901 has been described as "a veritable milestone in locomotive progress".<ref name="Locomotive Development in NZ">{{Cite web|url=https://nzetc.victoria.ac.nz/tm/scholarly/tei-Gov09_07Rail-t1-body-d3.html|title=Locomotive Development. — in — New Zealand — The "Pacific" Type. its Genesis and Triumph. &#124; NZETC|website=nzetc.victoria.ac.nz}}</ref> On many railways worldwide, Pacific steam locomotives provided the motive power for [[express passenger train]]s throughout much of the early to mid-20th century, before either being superseded by larger types in the late 1940s and 1950s, or replaced by [[electric locomotive|electric]] or [[diesel locomotive|diesel-electric]] locomotives during the 1950s and 1960s. Nevertheless, new Pacific designs continued to be built until the mid-1950s.

The type is generally considered to be an enlargement of the [[4-4-2 (locomotive)|{{nowrap|4-4-2}} Atlantic]] type, although its [[NZR Q class (1901)|prototype]] had a direct relationship to the [[4-6-0|{{nowrap|4-6-0}} Ten-wheeler]] and [[2-6-2|{{nowrap|2-6-2}} Prairie]], effectively being a combination of the two types.<ref name="Pacific Type">{{cite web|title=4-6-2 "Pacific" Locomotives in the USA|url=http://www.steamlocomotive.com/locobase.php?country=USA&wheel=4-6-2|website=Steam Locomotive}}</ref> The success of the type can be attributed to a combination of its four-wheel leading truck which provided better stability at speed than a [[2-6-2|{{nowrap|2-6-2}} Prairie]], the six driving wheels which allowed for a larger boiler and the application of more tractive effort than the earlier {{nowrap|4-4-2}} Atlantic, and the two-wheel trailing truck, first used on the New Zealand [[2-6-2|{{nowrap|2-6-2}} Prairie]] of 1885. This permitted the [[Firebox (steam engine)|firebox]] to be located behind the high driving wheels and thereby allowed it to be both wide and deep, unlike the {{nowrap|4-6-0}} Ten-wheeler which had either a narrow and deep firebox between the driving wheels or a wide and shallow one above.

The type is well-suited to high speed running.{{cn|date=December 2023}} The world speed record for steam traction of {{convert|126|mph|km/h|abbr=off}} has been held by a British Pacific locomotive, the [[LNER Class A4 4468 Mallard|''Mallard'']], since 3 July 1938.

===Development===
The two earliest {{nowrap|4-6-2}} locomotives, both created in the United States, were experimental designs which were not perpetuated. In 1887, the [[Lehigh Valley Railroad]] experimented with a {{nowrap|4-6-0}} Ten-wheeler design with a Strong's patent firebox, a cylindrical device behind the cab which required an extension of the frame and the addition of two trailing wheels to support it. In 1889, the [[Milwaukee Road|Chicago, Milwaukee & St Paul Railway]] rebuilt a conventional {{nowrap|4-6-0}} with trailing wheels as a means of reducing its axle load.<ref name="Ellis 1981">Ellis, Hamilton. (1981). ''The Pictorial Encyclopaedia of Railways''. Hamlyn. pp.104–105.</ref>

In 1896, six [[WAGR Q class (1895)|Q class]] {{nowrap|4-6-2}} tank locomotives were introduced on the [[Western Australian Government Railways]].

The first true Pacific, designed as such with a large firebox aft of the coupled wheels, was ordered in 1901 by the [[New Zealand Railways Department]] (NZR) from the [[Baldwin Locomotive Works]] of Philadelphia, Pennsylvania. The NZR Chief Mechanical Engineer, [[Alfred Beattie]], ordered thirteen new [[NZR Q class (1901)|Q class]] locomotives with a sufficiently large [[Wootten firebox|Wootten]] [[Firebox (steam engine)|firebox]]  to efficiently burn poor grade [[lignite|lignite coal]] from eastern [[South Island]] mines. Even before they had completed the order from New Zealand, the Baldwin engineers realised the advantages of this new type, and incorporated it into standard designs for other customers. The design was soon widely adopted by designers throughout the world.<ref name="Locomotive Development in NZ"/>

===Origin of the name===
There are different opinions concerning the origin of the name Pacific. The design was a natural enlargement of the existing Baldwin {{nowrap|4-4-2}} Atlantic type, but the type name may also be in recognition of the fact that a New Zealand designer had first proposed it.<ref name="Locomotive Development in NZ"/> Usually, however, new wheel arrangements were named for, or named by, the railroad which first used the type in the United States. In the case of the Pacific, that was the [[Missouri Pacific Railroad]] in 1902.<ref name="Pacific Type"/>

In the [[Cape Colony|Cape of Good Hope]] in South Africa, the first Pacifics were delivered from [[Kitson & Company]] in 1903 and designated the [[South African Class 5A 4-6-2|Karoo Class]], from the region of the Cape Western System of the [[Cape Government Railways]] that they were designed to work in.<ref name="Holland 1"/>

===Global popularity===
The Pacific type was used on mainline railways around the world. The railways of New Zealand and Australia were the first in the world to run large numbers of Pacific locomotives, having introduced {{nowrap|4-6-2}} types in 1901 and 1902 respectively and operating them until the 1960s.<ref name="Locomotive Development in NZ"/>

[[Image:PRR K5 5698.jpg|thumb|left|Builder's photograph of Altoona-built K5 no. 5698, 1929]]
During the first half of the 20th century, the Pacific rapidly became the predominant passenger steam power in North America. Between 1902 and 1930, about 6,800 locomotives of the type were built by North American manufacturers for service in the United States and Canada. With exported locomotives included, about 7,300 were built in total. About 45% of these were built by the [[American Locomotive Company]] (ALCO) which became the main builder of the type, and 28% by Baldwin. Large numbers were also used in South America, most of which were supplied by manufacturers in the United Kingdom, the United States and Germany.<ref name="Pacific Type"/>

[[File:SAR Class 5 (4-6-2).jpg|thumb|[[Cape Government Railways]] Enlarged Karoo Class, SAR Class 5]]
Africa was the third continent upon which the Pacific was regularly used, following the introduction of the Karoo class on the [[Cape Government Railways]] in the Cape of Good Hope in 1903. The earliest African examples were built in the United Kingdom by [[Kitson & Company]].

The earliest examples of the Pacific in Europe were two French prototypes, introduced in 1907 and designed by the ''[[Compagnie du chemin de fer de Paris à Orléans]]'' (PO) to overcome the insufficient power of their {{nowrap|4-4-2 Atlantics}}. Within a few weeks, these were followed by a German Pacific type that, although already designed in 1905, only entered service in late 1907. The next was a British type, introduced in January 1908. By the outbreak of [[World War I]], the type was being widely used on the railways of [[Continental Europe]].

The Pacific type was introduced into Asia in 1907, the same year that it was first used in Europe. By the 1920s, Pacifics were being used by many railways throughout the Asian continent.

In 1923, the Pacific gave its name to [[Arthur Honegger]]'s orchestral work, ''[[Pacific 231]]'', which successfully reflectively interprets the emotive sounds of a steam locomotive. (231 after the French system of counting axles rather than wheels.)

===Tank locomotives===
During the first two decades of the 20th century, the Pacific wheel arrangement enjoyed limited popularity on [[tank locomotives]]. On a {{nowrap|4-6-2T}} locomotive, the trailing wheels support the [[Tank locomotive#Fuel bunker|coal bunker]] rather than an enlarged firebox and such a locomotive is therefore actually a tank engine version of the [[4-6-0|{{nowrap|4-6-0}} Ten-wheeler]] tender locomotive. Indeed, many of the earliest examples were either rebuilt from tender locomotives or shared their basic design.

Around 1920, it became apparent to designers that the {{nowrap|4-6-2T}} wheel arrangement allowed a too limited bunker size for most purposes, with the result that most later designs of large suburban tank classes were of the [[4-6-4|{{nowrap|4-6-4T}} Hudson]] or [[2-6-4|{{nowrap|2-6-4T}} Adriatic]] wheel arrangement.

===Lifespan===
[[File:60163 Tornado 1.jpg|thumb|The [[LNER Peppercorn Class A1 60163 Tornado]], built in 2008]]
The Pacific became the major [[Express passenger train|express passenger]] locomotive type on many railways throughout the 1920s, 1930s and 1940s. Examples were also built for fast [[freight]] and [[Mixed-traffic locomotive|mixed traffic]] duties. However, due to the increasing weight of trains during the 1940s, larger developments of the type became necessary in the United States and elsewhere. The most notable of these was the [[4-6-4|{{nowrap|4-6-4}} Hudson or Baltic]] type, which had a four-wheel trailing bogie that permitted an even larger firebox, albeit at a loss of some [[adhesive weight]], and the [[4-8-2|{{nowrap|4-8-2}} Mountain]] type which used an extra pair of driving wheels to deliver more tractive effort to the rails. Nevertheless, the Pacific type remained widely used on express passenger trains until [[Steam locomotive#The end of steam in general use|the end of steam traction]]. The last examples were built in the United Kingdom and Japan in the mid-1950s. [[British Rail]]ways introduced its [[BR Standard Class 6]] and [[BR Standard Class 7]] designs in 1951 and 1952, and the final United Kingdom design, the [[BR Standard Class 8]], in 1954.<ref name="Bruce">Bruce, Alfred. (1952). ''The Steam Locomotive in America: Its Development in the Twentieth Century''. W.W. Norton.</ref>

However, the story of the {{nowrap|4-6-2}} type did not end in the 1960s. One further mainline example of the [[LNER Peppercorn Class A1]], [[LNER Peppercorn Class A1 60163 Tornado|No. 60163 ''Tornado'']], was completed at [[Darlington]] by the [[A1 Steam Locomotive Trust]] in 2008. Designed to meet modern safety and certification standards, Tornado runs on the [[Network Rail|United Kingdom's rail network]] and on mainline-connected [[heritage railway]]s.<ref name="RM50Greatest2008">The Railway Magazine, 50 Great British Locomotives, Autumn/Winter 2008 special, p98, A bonus 51st entry: The 21st century steam miracle</ref>