Under the Whyte notation for the classification of steam locomotives, 4-8-2 represents the wheel arrangement of four leading wheels, eight powered and coupled driving wheels and two trailing wheels. This type of steam locomotive is commonly known as the Mountain type.
The Colony of Natal in South Africa and New Zealand were innovators of the 4-8-2 Mountain wheel arrangement. The Natal Government Railways (NGR) placed in service the first tank engines with the 4-8-2 arrangement, and the NGR was also first to modify tender locomotives to use a 4-8-2 wheel arrangement. The New Zealand Railways Department (NZR) introduced the first tender locomotives designed and built as 4-8-2.
In 1888, the Natal Government Railways placed the first five of its eventual one hundred Class D 4-8-2 tank locomotives in service. The locomotive was designed by William Milne, the locomotive superintendent of the NGR from 1877 to 1896, and was built by Dübs & Company. This was the first known use of the 4-8-2 wheel arrangement in the world.
In 1906, six NGR Class B 4-8-0 Mastodon locomotives, designed by D.A. Hendrie, NGR Locomotive Superintendent from 1903 to 1910, were modified to a 4-8-2 wheel arrangement by having trailing bissel trucks added below their cabs to improve their stability when hauling fast passenger trains. These altered Class B locomotives were the first 4-8-2 tender locomotives in the world.
The first locomotive to be designed and built as a 4-8-2 tender locomotive was New Zealand's X class, designed by Alfred Beattie and built by NZR's Addington Workshops in 1908. It was designed to haul heavy freight trains on the mountainous central section of the North Island Main Trunk and it is believed that this was the source of the "Mountain" name of the 4-8-2 type, although it is also possible that the name was originated by the Chesapeake & Ohio Railway in the United States, who named the type after the Allegheny Mountains. The X class was, however, not a typical Mountain type, since its trailing truck served to spread the axle load rather than to allow a larger and wider firebox. The trailing wheels were positioned well behind a narrow firebox, which itself sat above the coupled wheels, necessitating the same design compromise between coupled wheel diameter and grate size as on a 2-8-0 Consolidation or 4-8-0 Mastodon. A more common 4-8-2 design was a progression of the classic 4-6-2 Pacific layout, which featured a wide firebox positioned above the trailing truck and behind the coupled wheels, allowing for a wide and deep firebox as well as large coupled wheels.
The NGR in 1909 placed in service the first example of the more common Mountain design, when it commissioned five Class Hendrie D 4-8-2 tender locomotives. It was designed by Hendrie to handle coal traffic on the upper Natal mainline and, while it was based on the Class Hendrie B 4-8-0, it had the firebox positioned to the rear of the coupled wheels to make a larger grate and ashpan possible. To accomplish this, the plate frame was equipped with a cast bridle at the rear to accommodate the improved firebox design, which also necessitated the addition of a trailing truck. Five locomotives were built by the North British Locomotive Company and delivered in 1909. The 4-8-2 type went on to become the most widely used steam locomotive wheel arrangement in South Africa, with altogether thirty classes of both tank and tender versions eventually seeing service on the South African Railways.
In 1951, six 4-8-2 locomotives were built by North British Locomotive Company to the design of the South African Class 19D for the Angolan Caminho de Ferro de Benguela (CFB or Benguela railway) as their 11th Class.
Unlike some other countries which utilised the 4-8-2 design for heavy passenger duties, the Australian 4-8-2 was more typically used as a heavy goods locomotive with small coupled wheels and a very large firebox.
The first 4-8-2 in Australia was the 3 ft 6 in (1,067 mm) gauge Q class of the Tasmanian Government Railways. Nineteen were built in batches between 1922 and 1945 by Perry Engineering in South Australia, Walkers Limited of Maryborough, Queensland and Clyde Engineering of New South Wales. Until 1950, the class handled the majority of mainline goods trains around the state.
Armstrong Whitworth built ten 500 class 4-8-2 locomotives for the South Australian Railways in 1926. They were the most powerful locomotives in Australia at the time and the heaviest non-articulated locomotives yet built in the United Kingdom. In 1929, they were modified to 500B class 4-8-4 Northern locomotives.
The three-cylinder D57 class locomotive of the New South Wales Government Railways (NSWGR) was one of the largest and most powerful locomotives ever built in Australia. Twenty-five were built by Clyde Engineering from 1929. With their large 65 square feet (6 square metres) grates and 64,327 pounds-force (286 kilonewtons) tractive effort, they were put to good use on the steep, 1 in 33 (3%) and 1 in 40 (2½%) gradients leading out of Sydney on the New South Wales mainlines.
The D57 design was developed further in 1950 with the smaller cylindered D58 class, of which thirteen were built at the Eveleigh and Cardiff Locomotive Workshops of the NSWGR. This class proved to be less successful, suffering from reliability problems attributed to the rack and pinion valve gear that was used for the third cylinder instead of the Gresley-Holcroft valve gear that was used on the D57 class.
The Western Australian Government Railways (WAGR) introduced two classes of 4-8-2 locomotive for freight haulage on the state's 3 ft 6 in (1,067 mm) network. The first was the S class, of which ten were built at the WAGR Midland Railway Workshops from 1943, with the locomotives named after West Australian mountains. The second was the W class, of which 64 were built by Beyer, Peacock & Company in 1951 and 1952. The 4-8-2 layout allowed for the weight of these relatively powerful locomotives to be spread over a number of axles, resulting in the W class having a maximum axle load of less than 10 tons. It also enabled the incorporation of a wide firebox for burning poor-quality coal.
In 1951, the Tasmanian Government Railways purchased a modern 4-8-2 locomotive, the H class. Eight locomotives were built by Vulcan Foundry for freight train working.
In 1941, the Bulgarian State Railways (BDZ) placed an order with Henschel & Son in Germany for fifty BDZ class 03 express passenger locomotives. They were of the type 2′D1′h3S (2-4-1 axle arrangement, simple steam expansion, superheating, three-cylinder, fast train service) and were designed to be capable of hauling heavy passenger trains over the often severe profiles of the 4 ft 8+1⁄2 in (1,435 mm) standard gauge Bulgarian mainlines, with gradients of up to 2.8%.
The first two locomotives were delivered by the end of 1941. During trials, it proved that the specifications of the BDZ designing engineers were correct and that they had successfully overcome the shortcomings of insufficient power and some construction problems that had been experienced with the BDZ 2-8-2 Mikado class 01 1′D1′h2S and class 02 1′D1′h3S locomotives. Mass production began the following year, but was interrupted by war restrictions introduced by the German authorities and delivery was halted before the full order was filled. Only ten more locomotives were built and delivered at the end of 1942 and early 1943, and the total number of the BDZ class 03 remained at twelve locomotives, numbered 03.01 to 03.12.
After 1958, these locomotives were gradually converted to mixed fuel oil and coal firing, which resulted in improved steaming ability and better performance, particularly on mountainous lines. During their 35 years of service, they exhibited excellent performance and only minor problems were experienced, such as oval wearing of the leading axle's inside crank. After factory repair, one of these locomotives, no. 03.12, was preserved in the depot at Gorna Oryahovitsa and returned to operation for tourist trains.
The Angus Shops of Canadian Pacific (CP) built a pair of 4-8-2 locomotives in 1914. While they were not replicated, CP kept them in service for thirty years. CP reverted to 4-6-2 Pacific locomotives before moving on to the 4-6-4 Hudson.
Canadian National operated eighty U-1 class 4-8-2 locomotives in passenger service, built by Montreal Locomotive Works in 1944. The last twenty, designated the U-1-f class, were delivered with semi-streamlined conical smokebox covers that earned them the nickname of Bullet Nose Bettys.
The Czechoslovak State Railways (ČSD) introduced the 498.0 class 4-8-2 express passenger locomotive in 1938, after successful trials in the Tatra Mountains to compare it to an alternative 2-8-4 Berkshire prototype. In 1954, the design was developed further into the 498.1 class. These technically sophisticated locomotives were reputedly capable of 11% thermal efficiency.
The ČSD also built a lighter and more numerous 475 class 4-8-2 locomotive.
In France, the 4-8-2 Mountain, known as the 241 type based on its axle arrangement, began to be used on the more undulating routes as increasingly heavy loads, brought about by the introduction of all-steel passenger cars after 1918, began to overtax the hill-climbing capabilities of the existing 2-8-2 Mikado and the speed capabilities of 4-6-2 Pacifc locomotives. Altogether 275 4-8-2 locomotives were built for French service.
In March and July 1973, twelve reboilered South African Railways Class 15BR locomotives, built by Montreal Locomotive Works (MLW) in Canada between 1918 and 1922, were sold to Caminhos de Ferro de Moçambique (CFM), the Mozambique Railways, where they were mainly used for shunting at Lourenco Marques and occasionally on freight service to Swaziland.
The first of eighteen X class 4-8-2 De Glehn compound locomotives, designed by Alfred Beattie, the Chief Mechanical Engineer of the New Zealand Railways Department (NZR) between 1900 and 1913, was built by the NZR's Addington Workshops in Christchurch in 1908. The first locomotive in the world to be designed and built as a 4-8-2 tender locomotive, it was designed to haul heavy freight trains on the newly completed mountainous central section of the North Island Main Trunk. One member of the pioneering X class survives and is currently located at the depot of the Feilding and District Steam Rail Society.
Between 1940 and 1956, 91 J and JA class locomotives entered service. Of these, 56 were built by North British Locomotive Company and 35 by the Hillside Railway Workshops in Dunedin. These locomotives survived in service until 1971 and were the last in-service steam locomotives on the NZR. Ten have been preserved.
The Manila Railroad, now the Philippine National Railways, operated two classes before and after World War II. The first class was the pre-war 170 class. Ten locomotives were built in 1921 by Alco. Three units were refurbished after being damaged by the war. In 1948, another ten locomotives, numbered the 100-class, were ordered from the Pennsylvania-based Vulcan Iron Works. Another 10 were built in 1948. Both the rebuilt 170 class and the new 100 class were decommissioned starting 1956, when MRR ordered the replacement of all its steam locomotives with diesel locomotives such as the GE UM12C. None of these locomotives were preserved like all of MRR's steam locomotives.
In 1931 three Pu29 mountains were delivered to PKP. They were used predominantly to pull heavy trains between East Prussia exclave and main territory of Germany, transiting through the Polish Pomerania, also known as the Polish Corridor.
Two 4-8-2 locomotives were built in 1952 by Henschel & Son to the design of the South African Class 19D, for the Nkana copper mines in Northern Rhodesia (now Zambia). They were numbered 337 and 338 in the Rhodesia Railways 19th class number range.
A lighter version of the South African Class 4A 4-8-2 was built for the Rhodesia Railways (RR) by North British Locomotive Company (NBL) in 1921. It was designated the RR 10th Class and was used on the long section south of Bulawayo in Southern Rhodesia (now Zimbabwe) through Bechuanaland Protectorate (now Botswana) to Mafeking in the Cape Province. Like the South African Class 4A, the RR 10th Class had a combustion chamber, the only RR locomotive class with this feature.
Between 1951 and 1953, 21 4-8-2 locomotives were built for RR by Henschel & Son to the design of the South African Class 19D, as their 19th class and 19C class. Their tenders were similar to the South African version's Torpedo type, but with plate frame instead of Buckeye bogies. One of these, the sole RR 19C class, was built as a condensing locomotive.
In 1955, four more, without superheating and numbered from 1 to 4, were built to the design of the South African Class 19D by NBL for the Wankie Colliery in Southern Rhodesia.
Of the thirty classes of 4-8-2 locomotives to see service on the South African Railways (SAR), four were tank locomotives.
Between 1909 and 1953, when the Class 25 and Class 25NC 4-8-4 Northern locomotives arrived on the scene, 4-8-2 Mountain tender locomotives became the most popular goods locomotives on South African rails. Between 1906 and 1938 altogether 26 different classes of 4-8-2 locomotives were acquired for mainline and branch line service.
In 1906, the NGR modified six of its Class B 4-8-0 Mastodon locomotives, built by NBL in 1904, to Class Altered B locomotives in order to improve their stability on passenger trains. This made them the first tender locomotives in the world with a 4-8-2 wheel arrangement. In 1912, they were classified as Class 1B by the SAR.
The SAR Class 3 originated on the NGR. Three variants were introduced between 1909 and 1912.
The Class 4 originated on the Cape Government Railways (CGR). Two variants were introduced in 1911 and 1913.
Three Class 12 variants were introduced by the SAR between 1912 and 1920.
Four Class 14 variants were introduced by the SAR between 1913 and 1918.
Seven Class 15 variants were introduced by the SAR between 1914 and 1938.
Five Class 19 variants were introduced by the SAR between 1928 and 1937.
In 1938 and 1939, the SAR placed 136 Class 23 locomotives in service, its last and largest Mountain locomotive. Designed by Day, it was intended as a general utility locomotive capable of operating on 80 pounds per yard (40 kilograms per metre) rail and was built in two batches by Berliner Maschinenbau and Henschel & Son in Germany. The original order in 1938 was for twenty locomotives, of which Berliner built seven and Henschel thirteen. However, the urgency brought about by the rapidly deteriorating political climate in Europe at the time led to a further 116 locomotives being ordered even before the first batch could be delivered and tested. Of these, Henschel built 85 and Berliner 31. The last locomotive of this second order was delivered in August 1939, just one month before the outbreak of the Second World War. Since they were intended for working in the arid Karoo, they were equipped with very large tenders with a high water capacity that rode on six-wheeled bogies.
Spain had more than 200 Mountain locomotives, known as the 241 type, in five classes.
The first type to be introduced, although earlier by only a few weeks, was the NORTE 4000 class, 4001–4047 in 1925 and 4049–4066 later. This was a huge four-cylinder compound machine with a 163.5 tonnes (160.9 long tons; 180.2 short tons) working order weight and 1,750 mm (5 ft 9 in) coupled wheels, a diameter that was believed to be ideal for passenger locomotives in the mountainous Peninsula. It performed very well on heavy express trains from Madrid to the French border in Irun. Although built in Spain, the type was of German design.
Compañía de los Ferrocarriles de Madrid a Zaragoza y Alicante (MZA) commissioned the 1700 type (1701–1795), built by La Maquinista Terrestre y Marítima (MTM) in Barcelona. It was a rude two-cylinder simple expansion locomotive, also with 1,750 mm (5 ft 9 in) coupled wheels and slightly lighter than its NORTE counterpart, with the first ones of 1925 at 159.5 tonnes and the last ones of 1930 at 163.44 tonnes.
A controversy arose in Spain between the defenders of these two types. The 4000 was slightly more powerful, but the simplicity and reliability of the Spanish-designed 1700 was preferred.
The MZA commissioned an enhanced 1700 type, designed with a streamlined casing á la mode and designated the 1800 type. The Spanish Civil War interrupted construction and the ten machines were only completed after the war was ended in 1939. Although well designed and good performers in theory, they lacked the advantages of streamline casing and especially suffered from problems associated with the high-pressure boiler that needed specially designed lubricators that were not available in the impoverished post-war Spain.
The NORTE launched the 4648 just before RENFE was established in 1941. It was an enhanced 4600 type with new designed cylinders after the proposals of André Chapelon. The locomotive was slightly more powerful than her sisters and RENFE commissioned 28 more to be built between 1946 and 1948. The increased capacity of the new machines never reached its full potential, however, due to the lack in maintenance typical of post-war Spain.
In 1944, RENFE commissioned the 2700 type to run on former MZA lines. The type used the high-capacity boiler designed for the 2-10-2 Santa Fe type of 1942. They were very powerful machines with weights exceeding 204 tonnes and with 1,750 mm (5 ft 9 in) coupled wheels. They performed well and were appreciated by the crews who called them Bonitas (prettys). A coal-fired and stoker-equipped design, they were converted to oil-firing in the 1950s. Construction ceased in 1952, with 57 locomotives built. The last one was retired in 1973. One is preserved (241-2238F) in Móra la Nova (Tarragona, Catalonia, Spain) for the APPFI enthusiast association, with the intention to restore it to running order.
The United Kingdom's entire population of Mountain locomotives consists of Hercules and Samson, the two 15 in (381 mm) gauge 4-8-2 locomotives of the 13+1⁄2-mile (21.7-kilometre) Romney, Hythe & Dymchurch Railway in Kent, England. The locomotives were built by Davey Paxman in 1927.
The Southern Railway considered using 4-8-2s for express trains before changing to the 2-8-2 and eventually 4-6-2 design, leading to the Bulleid pacifics. The London and North Eastern Railway had designs for 4-8-2s, but during WWII the British government forbid the development of express passenger locomotives, so the plans were dropped. Following the LNER chief mechanical engineer Sir Nigel Gresley’s death from illness in 1941, neither Edward Thompson nor Arthur Peppercorn resumed the 4-8-2 project, and after the United Kingdom nationalized private railway companies into British Railways in 1948, only 4-6-2s were pursued as express locomotives with the BR Standard Class 6 and 7 (though they were classified as mixed-traffic), as well as rebuilt versions of the aforementioned 4-6-2s of Bulleid’s design, which would last until dieselization.
The 4-8-2 was most popular on the North American continent. When the 4-6-2 Pacific fleets were becoming over-burdened as passenger trains grew in length and weight, the first North American 4-8-2 locomotives were built by the American Locomotive Company (ALCO) for the Chesapeake & Ohio Railway (C&O) in 1911. It is possible that the "Mountain" name was originated by C&O, after the Allegheny Mountains where their first 4-8-2 locomotives were built to work. ALCO combined the traction of the eight-coupled 2-8-2 Mikado with the excellent tracking qualities of the Pacific's four-wheel leading truck. Although C&O intended their new Mountains for passenger service, the type also proved ideal for the new, faster freight services that railroads in the United States were introducing. Many 4-8-2 locomotives were therefore built for dual service.
A total of about 2,200 Mountain type locomotives were built for 41 American railroads. With 600 4-8-2 locomotives, the largest user in the United States was the New York Central Railroad (NYC), who named theirs the Mohawk type.
Other large users in the United States were the Pennsylvania Railroad with 224 Class M1, Class M1a and Class M1b locomotives that were used mostly for fast freight service, the Florida East Coast with ninety passenger locomotives, the New York, New Haven & Hartford Railroad with seventy, and the Southern Railway with fifty-eight. The heaviest 4-8-2s in the world were the twenty-three St. Louis–San Francisco Railway 4400 class locomotives, built by the railroad between 1939 and 1945, using boilers from older 2-10-2 locomotives, riding cast frames, and weighing over 449,000 pounds. These were a follow-up to the road's 4300 class, similarly rebuilt at the road's Springfield, Missouri shops with some parts from 2-10-2s and new cast frames, but with new 250 psi boilers; these appear to be the most powerful Mountain types, tested by the railway's dynamometer at 4800 horsepower.
The Southern Pacific ordered a total of seventy-five MT-class 4-8-2s from ALCO for both freight and passenger service.
One notable example is SLSF 1522, one of thirty T-54 class Mountains built by Baldwin in 1926 and became one of two American 4-8-2 to have had an excursion career with the other being Illinois Central 2613. It ran excursions between 1988 until 2002, when rising insurance rates and a flue sheet cracked beyond repair forced it back into retirement. 1522 is now on display at the National Museum of Transportation in St Louis.
Some of the more notable preserved Mountains worldwide are listed here by country of origin.
Media related to 4-8-2 locomotives at Wikimedia Commons
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