4-8-2

Union Pacific Railroad class MT-1 4-8-2 #7000.

Under the Whyte notation for the classification of steam locomotives, 4-8-2 represents the wheel arrangement of four leading wheels on two axles (usually in a leading truck), eight powered and coupled driving wheels on four axles, and two trailing wheels on one axle (usually in a trailing truck). This type of steam locomotive is also known as the Mountain type.^[1]

Other equivalent classifications are:
UIC classification: 2′D1′ (also known as German classification and Italian classification)
French classification: 241 (also known as Spanish classification)
Russian classification: 2-4-1
Turkish classification: 47
Swiss classification: 4/7

History

Both the tank engine and tender engine versions of this wheel arrangement were designed in South Africa and built in the UK.

South Africa

Natal Government Railways Class A 105 (4-8-2T), later SAR 151

SAR Class 23 2556 (4-8-2), built by Berliner Maschinenbau

The first 4-8-2 tank locomotive was designed by William Milne, locomotive superintendent of the Natal Government Railways in 1887. One hundred examples were built by Dübs and Company. They later became SAR Class A, and twenty-one were later converted into tender locomotives.^[2] Twenty five further tank engines were designed by Milne's successor, David Hendrie, and built by Dübs for the same railway in 1904 later becoming SAR Class G. Between 1910 and 1922 a number of Class H 4-10-2T were rebuilt as 4-8-2T to give them a better turning circle. These became SAR classes H1 and H2.^[3]

In 1906, six Class 1 4-8-0 tender locomotives were rebuilt as 4-8-2, in order to improve their stability on passenger trains, and these became SAR Class 1B.^[4] Thereafter the 4-8-2 became one of the most common locomotive types in South Africa with SAR Classes 3, 4, 12 & 15 built by the North British Locomotive Company between 1909 and 22; and Classes 19 & 23 built by Berliner Maschinenbau, between 1928 and 1936.^[5]

New Zealand

The first of 18 X class 4-8-2 De Glehn compound locomotives were designed by A. L. Beattie and built by New Zealand Railways Department's Addington Workshops in Christchurch in 1908. It was designed to haul heavy freight trains on the mountainous central section of the North Island Main Trunk Railway. It is possible that this was the source of the "Mountain" nickname that was applied to the 4-8-2 type, though it is often said the name originates from the Chesapeake and Ohio Railway in the United States, who named the type "Mountain" after the Allegheny Mountains their first 4-8-2s were built to tackle.

One member of the pioneering X class survives and is currently located at the depot of the Feilding and District Steam Rail Society.

Although the X class was the first 4-8-2 locomotive, it is perhaps not a classic example of the type. The X class' trailing truck was positioned well behind a narrow firebox which itself sat above the driving wheels,^[6] necessitating the same design compromise between driving wheel diameter and boiler/grate size as a 2-8-0 or 4-8-0 design. Later, more successful 4-8-2 designs were a progression of the classic 4-6-2 layout, which featured a wide firebox positioned above the trailing truck and behind the driving wheels, allowing for a large firebox as well as large driving wheels.

USA

The 4-8-2 was most popular on the North American continent, where 4-6-2 Pacifics were becoming over-burdened as passenger trains grew in length and weight. The first North American 4-8-2 locomotives were built by ALCO for the Chesapeake and Ohio Railway in 1911. ALCO combined the traction of the eight-drivered 2-8-2 "Mikado" with the excellent tracking qualities of the Pacific's four-wheel leading truck.

Although the C&O intended their new Mountains for passenger service, the type proved ideal for the new, faster freight service the railroads were introducing. Many 4-8-2s were built for dual service.

Mountain type locomotives were built for 41 American railroads; about 2,200 were built. The largest users were the New York Central Railroad with 435 of what they named the Mohawk type (the Water Level Route had no need for "Mountains", after all); the Pennsylvania Railroad with 224 class M1, M1a and M1b locomotives, used mostly for fast freight service; the Florida East Coast with 90 passenger locomotives; the New Haven with 70; and the Southern Railway with 58. The heaviest 4-8-2s were the twenty Illinois Central 2600 class built by the railroad 1945-46; close behind were B&M, L&HR, and D&RGW.

Canada

The Canadian National Railway operated eighty U-1 class 4-8-2 locomotives in passenger service (#6000–6079). Its last twenty (6060–6079) were delivered in 1944 with semi-streamlined conical smokebox covers that earned the nickname of “Bullet Nose Bettys”. Canadian Pacific Railway's Angus Shops built a pair of 4-8-2s in 1914. While they were not replicated, CP kept them in service for 30 years. CP reverted to 4-6-2 Pacifics before moving to the 4-6-4 Hudson.^[7]

European use

Britain

Britain's population of Mountain locos consists entirely of two 15 in (381 mm) gauge locomotives on the Romney, Hythe and Dymchurch Railway, built by Davey Paxman & Co. in 1926. A number of Mountains were built for export; particularly the North British built J, Ja and Jb classes for secondary lines in New Zealand.

BDZ 03.06 at Henschel yard, 1942

Bulgaria

In 1941 Bulgarian State Railways (BDZ) placed an order with Henschel & Sohn – Kassel (Germany) for the building of 50 1,435 mm (4 ft 8 ¹⁄₂ in) standard gauge express passenger locomotives of type 2′D1′h3S (axle arrangement 2-4-1, simple steam expansion, superheating, 3-cylinder, fast train service), capable of hauling heavy passenger trains over the often severe profiles of Bulgarian main lines with gradients up to 2.8% (1 in 35.7). The first two engines were delivered by the end of 1941 and quickly proved the correctness of the specification of the BDZ engineers, who had previously experienced the insufficient power and some construction problems with classes 01 (1′D1′h2S) and 02 (1′D1′h3S). Next year mass production began, but was interrupted by war restrictions introduced by the German authorities; delivery ceased before the order was filled. Only 10 more engines were built and delivered, at the end of 1942 through the beginning of 1943, so the total number of the new BDZ class 03 remained 12 engines (03.01 – 03.12). After 1958 they were gradually converted to mixed fuel oil and coal firing, which resulted in improved steam production and facilitated service, particularly on mountainous lines. For about 35 years of use they showed excellent performance and minor problems (oval wearing of leading axle's inside crank). One of these machines, 03.12 (serial No. 26575) after factory repair was preserved in the depot of Gorna Oryahovitsa and is now completely restored and returned to operation under steam for tourist trains [1].

Technical specifications:

Czechoslovakia

Czech Railways 'Mountain' type locomotive No. 475.132 on a freight at Česká Lípa station in July 1975

The CSD introduced the 498.0 class 4-8-2 express passenger locomotive in 1938 after successful trials in the Tatra Mountains against an alternative 2-8-4 prototype. The design was further developed in 1954 into the 498.1 class. These technically sophisticated locomotives were reputedly capable of 11% thermal efficiency.^[8]

CSD also built a lighter and more numerous 4-8-2 class, numbered in the 475.xxx series.

France

Preserved SNCF 241 P class locomotive 241 P 17 on an excursion run in 2008.

In France, these locomotives (known as the 241 type) were used on more undulating routes as increasingly heavy loads (caused by the use of all-steel passenger cars after 1918) began to overtax the hill-climbing capabilities of the existing 4-6-2 and the speed capabilities of 2-8-2 locomotives. Two hundred and seventy-five 4-8-2's were built for French service.

• The Chemins de fer de l'Est railway took delivery of a prototype 4-8-2 four-cylinder compound locomotive, first numbered 41001, from its own Épernay shops in 1925. This was the first Mountain type built for commercial service within France.
• The Est subsequently ordered 40 production locomotives (241-002 to 241-041) based on the prototype design, with improvements, in 1930. Their delivery took place over the following three years.
• The Chemins de Fer de l'État (État) obtained 49 copies of the Est design in 1930–1932, numbered 241-001 to 241-049. Under SNCF management after 1938, these locomotives were transferred to the Est region and finished their service there.
• The Chemins de fer de Paris à Lyon et à la Méditerranée (PLM) introduced a class of 145 bullet-nosed 241 A compound Mountain types in 1925 to accelerate trains over the Seuil de Bourgogne incline. This four cylinder compound locomotive was unusual in having short connecting rods for the outside (high pressure) cylinders pivoted on the first driving axle, rather than the second as is typical of most six or eight coupled wheel locomotives. Perhaps as a result of this, the locomotive did not run smoothly at speeds of greater than 100 km/h (63 mph). In order to save weight, the built-up locomotive frames were lightly constructed, which led to torsion and flexing which caused the wheel bearings to overheat. This problem was never solved on the PLM engines. However, true to the "Mountain" type they were able to haul heavy passenger trains over gradients at speed, taking an 800 tonne load over a 1 in 200 gradient at 90 to 100 km/h (56 to 63 mph).
• Based on the 241 A, the unique PLM 241 C 1 (built 1930) had connecting rods linking the second and third driving axles. This locomotive served as the pattern for the development of the postwar standard SNCF 241 P class.
• The PLM also experimented with a high-pressure watertube boiler on the unique PLM 241 B 1 prototype, constructed with a German Schmidt-Henschel boiler in 1930. It was soon learned that this locomotive was a failure and it was retired and broken up by the mid-1930s.
• The État also built a prototype 3 cylinder simple-expansion 4-8-2 in 1932 (241.101) which was an embarrassing failure for the company, but which was later converted by André Chapelon into the legendary 242 A 1 4-8-4 locomotive.^[9]
• The SNCF, with design input from André Chapelon, developed the earlier PLM 241 C into the 35-strong 241 P class in 1948.^[10] These locomotives, although prone to axlebox problems caused by a frame not rigid enough for the (4000 indicated horsepower) output of the cylinders, were nevertheless very effective and some were still running into the early 1970s.

RENFE standard 4-8-2 on a freight at Zaragoza Arabal, August 1970

Spain

RENFE (ex-MZA) 4-8-2 at Salamanca shed, August 1970

Spain saw over 200 of these locomotives, also known as a 2-4-1, in five classes.

Australia

Unlike other countries which utilised the 4-8-2 design for heavy passenger use, in Australia the 4-8-2 was more typically a heavy freight locomotive with small driving wheels and a very large firebox. The first 4-8-2s in Australia were 3 ft 6 in (1,067 mm) gauge Q class of the Tasmanian Government Railways from 1922.^[11]

Armstrong Whitworth built ten 500 class 4-8-2s for the South Australian Railways in 1926, which at the time were the most powerful locomotive in Australia and the heaviest non-articulated locomotives built in Great Britain. Then, the three-cylinder NSWGR D57 class of 1929 was one of the largest and most powerful locomotives ever built in Australia. With a large 65 sq ft (6.04 m²) grate and 64,327 lbf (286.1 kN) tractive effort,^[12] they were put to good use on the steep 1 in 40 (2.5%) gradients leading out of Sydney on NSW's mainlines. The design was further developed in 1950 with the smaller cylindered D58 class. However, this class proved to be less successful, suffering reliability problems attributed to the rack and pinion valve gear for the third cylinder used instead of the D57's Gresley/Holcroft valve gear.

The Western Australian Government Railways introduced two classes of 4-8-2 locomotive for freight haulage on the state's 3 ft 6 in (1,067 mm) network, the S class of 1943 and W class of 1951. The 4-8-2 layout allowed for the weight of these relatively powerful locomotives to be spread over a number of axles (the W class had a maximum axle load of just 10 tons) and also enabled the incorporation of a wide firebox for burning poor quality coal. The Tasmanian Government Railways also purchased a modern 4-8-2 from Robert Stephenson and Hawthorns in 1951. This was their H class.^[11]

Other African Use

British-built 4-8-2 locomotives at Accra depot, Ghana Railways, 1974. 3'6" gauge, oil-firing, Giesl ejectors

References

• Paxton, Leith and Bourne, David (1985). Locomotives of the South African Railways. C. Struik (Pty) Ltd. ISBN 0-86977-211-2. 

• CHAVY, Marcel, MAILLET, Maurice, and GIBERT, Andre (1992). Les "Mountain" francaises. Les editions du Cabri. ISBN 2-908816-05-9.