In the Whyte notation for the classification of steam locomotive wheel arrangement, an 0-4-4-0 is a locomotive with no leading wheels, two sets of four driving wheels, and no trailing wheels. The arrangement is chosen to give the articulation of a locomotive with only the short rigid wheelbase of an 0-4-0 , but with its weight spread across eight wheels, and with all the weight carried on the driving wheels; effectively a flexible 0-8-0 . Articulated examples were constructed as Mallet, Meyer, BMAG and Double Fairlie locomotives and also as geared locomotives such as Shay, Heisler, and Climax types. [1] A similar configuration was used on some Garratt locomotives, but it is referred to as 0-4-0+0-4-0 . In the electric and diesel eras, the Bo-Bo is comparable and closest to the Meyer arrangement of two swivelling bogies.[ citation needed ]
Although rigid duplex locomotives were also constructed with pairs of driving axles and the 0-4-4-0 driven arrangement, these were intended for express passenger service and so were given 4-4-4-4 overall arrangements with leading and trailing bogies for stability.[ citation needed ]
A few Mallet locomotives were built as 0-4-4-0 tender locomotives, mostly by Baldwin for narrow gauge lines, but all others were 0-4-4-0T tank locomotives. As one of the main goals of this arrangement was to place the most adhesion weight on the drivers, it was sensible to include the weight of coal and water with this.
Other equivalent classifications are:
The first four-wheeled double-bogie locomotives were built by Horatio Allen in 1832. These were four double-boilered locomotives built by the West Point Foundry in New York for the South Carolina Canal and Rail Road Company, the first of these named South Carolina. Although these had many of the features that would later become known as typical for Fairlies, the articulated bogies and the double boiler, the wheels of these bogies were not coupled and so they were instead of a 2-2-0+0-2-2 wheel arrangement. The 'double boiler' in this case also meant two narrow boiler barrels side by side at each end, four in total, not just double-ended. [2]
The first 0-4-4-0 locomotive [lower-roman 1] was the Seraing , one of the contestants in the 1851 Semmering Trials. The Semmering railway was the world's first mountain railway and faced unprecedented gradients of 2.5%. This required the development of new techniques in locomotive design for which trials were held and the entrants used various forms of articulation in order to place the most useful power through their driving wheels. Seraing resembled what would become the double Fairlie design, with a double boiler and two articulated powered bogies beneath the frame. [2]
After Semmering, some French engineers also experimented with duplex drive locomotives. Jules Petiet, designed some unsuccessful classes of rigid duplexes with an 0-2-6-2-0 (UIC: A3A) single-boiler but double-ended Crampton in 1862 and a class of twenty 0-6-6-0 T s in 1863. [3] Thouvenot in 1863 produced an 0-6+6-0T design which was closer to the Fairlie type, with a double boiler and swivelling bogies. [2] [4]
The first Meyer locomotive, L'Avenir, was built in 1861 and was also derived from a Semmering Trials design, the Neustadt . This had a similar arrangement of two power bogies to Seraing, but a conventional single boiler. Meyer first used compounding and so the cylinders were placed at the inner end of the bogies, where the intermediate pressure pipework between them could be kept shorter.
The most numerous Meyer locomotives were a German 750 mm (2 ft 5+1⁄2 in) narrow gauge class, the DRG Class 99.51–60, of which 96 were built.
The need to place the boiler above the bogies limited the depth of the firebox. W. G. Bagnall worked around this by using their own boiler design with an internal firebox within the circular shell.
A decade after Seraing, Robert Fairlie revived the concept and was granted a patent for his design in 1864. [5] [6] It is not known how aware Fairlie was of the other European attempts. [2] Placing the cylinders at the outer ends of the power bogies left a space between them and allowed depth for a conventional firebox, grate and ashpan.
The first Fairlie was an 0-4-4-0T built for the Neath and Brecon Railway in 1866, but the design came to prominence in 1869 with Little Wonder for the Ffestiniog Railway in North Wales followed by five others. One locomotive was supplied to the Denver and Rio Grande Railroad in 1872. The type was also used in Mexico, New Zealand and Russia on Transcaucasian Railway.
There are five examples of surviving Fairlie 0-4-4-0T locomotives on the Ffestiniog Railway. Two of these are survivors from the original 19th century line; Merddin Emrys is still in service. Three were built new during the preservation era, the latest James Spooner, was completed in 2023.
Josephine, a Vulcan Foundry-built Double Fairlie, built in 1872 for the Dunedin and Port Chalmers Railway Company, [7] survives as a static exhibit in Dunedin, New Zealand.
These were a small Fairlie in all but name, with a few differences to allow a French patent to be granted in 1887. [8] They were employed over short distances in French 600 mm military railways. [8]
The most numerous 0-4-4-0 locomotives were the Mallet design. These are articulated compound locomotives. The rear wheels and cylinders were fixed to the frames, as for a conventional locomotive. The front set formed a bogie that was pivoted at its rear and supported the front of the boiler on a sliding pad. As a compound, the lower pressure cylinders were always the swivelling bogie, as this only required the lower intermediate pressure to be passed through the pivoting steam pipe. The first of these was for a 600 mm Decauville light railway in 1887. Like the Fairlies, these were intended for narrow gauge lines built with tight curves. [9] The most numerous 0-4-4-0T and 0-4-4-0TT Mallets were small locomotives of 600 mm and 750 mm gauge built for the Javan sugar plantations in the 1900s and 1910s by companies like Orenstein & Koppel and the Dutch Du Croo & Brauns, [10] some of which were still operating into the 21st century. [11]
Switzerland persisted with the 0-4-4-0T and 0-4-4-0 types and in the 1890s J.A. Maffei built classes of each for the standard gauge Swiss Central Railway. [12]
The Mallet type developed and outgrew the original wheel arrangement, particularly in the USA, also gaining tenders and often being simple expansion engines rather than compounds. [13]
Eritrean Railways used many 0-4-4-0Ts. [14] [15] The last was built in their own shops in 1963, making it the last Mallet built in the world.
From 1911, Italian State Railways built at least twelve 950 mm gauge Mallets as the FS R.440 class. These were used on the Palermo-Corleone-San Carlo Railway until the end of the 1920s, when they were relocated to Italian colonies in Eritrea.
The Semmering railway in Austria, which starts at Gloggnitz and leads over the Semmering to Mürzzuschlag, was the first mountain railway in Europe built with a standard gauge track. It is commonly referred to as the world's first true mountain railway, given the very difficult terrain and the considerable altitude difference that was mastered during its construction. It is still fully functional as a part of the Southern Railway which is operated by the Austrian Federal Railways.
Mason Bogie locomotives are a type of articulated tank locomotive suited for sharp curves and uneven track, once commonly used on narrow-gauge railways in the United States. The design is a development of the Single Fairlie locomotive.
A Mallet locomotive is a type of compound articulated steam locomotive, invented by the Swiss engineer Anatole Mallet (1837–1919).
A Fairlie locomotive is a type of articulated steam locomotive that has the driving wheels on bogies. The locomotive may be double-ended or single ended. Most double-ended Fairlies had wheel arrangements of 0-4-4-0T or 0-6-6-0T.
A Crampton locomotive is a type of steam locomotive designed by Thomas Russell Crampton and built by various firms from 1846. The main British builders were Tulk and Ley and Robert Stephenson and Company.
An articulated locomotive is a steam locomotive with one or more engine units that can move independently of the main frame. Articulation allows the operation of locomotives that would otherwise be too large to negotiate a railroad's curves, whether mainlines or special lines with extreme curvature such as logging, industrial, or mountain railways.
In the Whyte notation for classifying the wheel arrangement of steam locomotives, an 0-8-8-0 is a locomotive with two sets of eight driving wheels and neither leading wheels nor trailing wheels. Two sets of driving wheels would give far too long a wheelbase to be mounted in a fixed locomotive frame, so all 0-8-8-0s have been articulated locomotives of the Mallet type, whether simple or compound. In the UIC classification, this arrangement would be, refined to Mallet locomotives, (D)D. The type was sometimes called Angus in North America.
Under the Whyte notation for the classification of steam locomotives, a 0-6-6-0 wheel arrangement refers to a locomotive with two engine units mounted under a rigid locomotive frame, with the front engine unit pivoting and each engine unit with six coupled driving wheels without any leading or trailing wheels. The wheel arrangement was mostly used to describe Mallet locomotive types and in some occasions, Double Fairlie locomotives.
A Meyer locomotive is a type of articulated locomotive that has two separate bogies, upon which the boiler and firebox swivel. The design was never as popular as the Garratt or Mallet locomotives. It can be best regarded as 19th Century competition for the early compound Mallet and also the Fairlie articulated designs. Most single cab modern trains are of a similar design such as power cars, freight diesel locomotives, and some passenger locomotives.
Under the Whyte notation for the classification of steam locomotives by wheel arrangement, 2-6-6-0 is a locomotive with one pair of unpowered leading wheels, followed by two sets of three pairs of powered driving wheels and no trailing wheels. The wheel arrangement was principally used on Mallet-type articulated locomotives. Some tank locomotive examples were also built, for which various suffixes to indicate the type of tank would be added to the wheel arrangement, for example 2-6-6-0T for an engine with side-tanks.
Under the Whyte notation for the classification of steam locomotives by wheel arrangement, the 0-4-0+0-4-0 is an articulated locomotive of the Garratt type. The wheel arrangement is effectively two 0-4-0 locomotives operating back-to-back or face-to-face, with the boiler and cab suspended between the two power units. Each power unit has no leading wheels, four powered and coupled driving wheels on two axles and no trailing wheels. A similar arrangement exists for Mallet, Meyer and Fairlie locomotives, but is referred to as 0-4-4-0.
Under the Whyte notation for the classification of steam locomotives by wheel arrangement, a 2-8-2+2-8-2 is an articulated locomotive using a pair of 2-8-2 power units back to back, with the boiler and cab suspended between them. The 2-8-2 wheel arrangement has a single pair of leading wheels in a leading truck, followed by four coupled pairs of driving wheels and a pair of trailing wheels in a trailing truck. Since the 2-8-2 type was known as Mikado, the corresponding Garratt and Modified Fairlie types were usually known as Double Mikado.
Under the Whyte notation for the classification of steam locomotives, 0-6-0+0-6-0 represents the wheel arrangement of an articulated locomotive with two separate swivelling engine units, each unit with no leading wheels, six powered and coupled driving wheels on three axles and no trailing wheels. The arrangement is effectively two 0-6-0 locomotives operating back-to-back and was used on Garratt, Double Fairlie, Meyer and Kitson-Meyer articulated locomotives. A similar arrangement exists for Mallet steam locomotives on which only the front engine unit swivels, but these are referred to as 0-6-6-0.
The Engerth locomotive was a type of early articulated steam locomotive designed by Wilhelm Freiherr von Engerth for use on the Semmering Railway in Austria. The distinctive feature of the Engerth design was an articulated tender as part of the main locomotive frame. Some of the weight of the tender therefore rested on the driving wheels, improving adhesion, while articulation allowed the locomotive to navigate the narrow curves of mountain railways.
A compound locomotive is a steam locomotive which is powered by a compound engine, a type of steam engine where steam is expanded in two or more stages. The locomotive was only one application of compounding. Two and three stages were used in ships, for example.
The South African Railways Class FC 2-6-2+2-6-2 of 1925 was an articulated steam locomotive.
The South African Railways Class GH 4-6-2+2-6-4 of 1928 was an articulated steam locomotive.
The Cape Government Railways Fairlie 0-6-0+0-6-0 of 1876 was a South African steam locomotive from the pre-Union era in the Cape of Good Hope.
Under the Whyte notation for the classification of steam locomotives, 0-6-6 represents the wheel arrangement of no leading wheels, six powered and coupled driving wheels on three axles and six trailing wheels on three axles. All locomotives with this wheel arrangement were tank locomotives; no 0-6-6 tender locomotives were recorded.
A multiplex locomotive is a steam locomotive that divides the driving force on its wheels by using multiple pairs of cylinders to drive multiple driving wheel set groups. Such a locomotive will necessarily articulated if it has more than two sets of driving wheels. There were locomotive projects with three, four, five or six sets of drive wheels. However, these locomotives were never built, except for four triplex locomotives in the United States and one quadruplex locomotive in Belgium.