In theWhyte notation for the classification ofsteam locomotivewheel arrangement, an0-4-4-0 is a locomotive with noleading wheels, two sets of fourdriving wheels, and notrailing wheels. The arrangement is chosen to give thearticulation of a locomotive with only the short rigid wheelbase of an0-4-0, but with its weight spread across eight wheels, and with all the weight carried on the driving wheels; effectively a flexible0-8-0. Articulated examples were constructed asMallet,Meyer,BMAG andDouble Fairlie locomotives and also asgeared locomotives such asShay,Heisler, andClimax types.[1] A similar configuration was used on someGarratt locomotives, but it is referred to as0-4-0+0-4-0. In the electric and diesel eras, theBo-Bo is comparable and closest to the Meyer arrangement of two swivelling bogies.[citation needed]
Although rigidduplex 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 given4-4-4-4 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 0-4-4-0Ttank locomotives. As one of the main goals of this arrangement was to place the mostadhesion 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 byHoratio Allen in 1832. These were four double-boilered locomotives built by theWest Point Foundry inNew York for theSouth Carolina Canal and Rail Road Company, the first of these namedSouth 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 a2-2-0+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[i] was theSeraing [de], one of the contestants in the 1851Semmering Trials. TheSemmering 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 an0-2-6-2-0 (UIC: A3A) single-boiler but double-endedCrampton in 1862 and a class of twenty0-6-6-0Ts in 1863.[3]Thouvenot in 1863 produced an0-6+6-0T design which was closer to the Fairlie type, with a double boiler and swivelling bogies.[2][4]
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The first Meyer locomotive,L'Avenir, was built in 1861 and was also derived from a Semmering Trials design, theNeustadt [de]. This had a similar arrangement of two power bogies toSeraing, but a conventional single boiler. Meyer usedcompounding at first and so the cylinders were placed at the inner ends of the bogies, where the intermediate pressure pipework between them could be kept shorter.
The most numerous Meyer locomotives were a German750 mm (2 ft 5+1⁄2 in) narrow gauge class, theDRG Class 99.51–60, of which 96 were built.
The need to place the boiler above the bogies limited the depth of thefirebox.W. G. Bagnall worked around this by usingtheir own boiler design with an internal firebox within the circular shell.
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A decade afterSeraing,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 firstFairlie was an 0-4-4-0T built for theNeath and Brecon Railway in 1866, but the design came to prominence in 1869 withLittle Wonder for theFfestiniog Railway inNorth Wales followed by five others. One locomotive was supplied to theDenver and Rio Grande Railroad in 1872. The type was also used inMexico,New Zealand andRussia onTranscaucasian Railway.
There are five examples of surviving Fairlie 0-4-4-0T locomotives on theFfestiniog 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 latestJames Spooner, was completed in 2023.
Josephine, aVulcan Foundry-builtDouble Fairlie, built in 1872 for theDunedin and Port Chalmers Railway Company,[7] survives as a static exhibit inDunedin, New Zealand.[8]
These were a small Fairlie in all but name, with a few differences to allow a French patent to be granted in 1887.[9] They were employed over short distances in French600 mm military railways.[9]
The most numerous 0-4-4-0 locomotives were theMallet design. These arearticulatedcompound 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 a600 mmDecauville light railway in 1887. Like the Fairlies, these were intended for narrow gauge lines built with tight curves.[10] The most numerous 0-4-4-0T and 0-4-4-0TT Mallets were small locomotives of 600 mm and750 mm gauge built for theJavan sugar plantations in the 1900s and 1910s by companies likeOrenstein & Koppel and the DutchDu Croo & Brauns,[11] some of which were still operating into the 21st century.[12]
Switzerland persisted with the 0-4-4-0T and 0-4-4-0 types and in the 1890sJ.A. Maffei built classes of each for thestandard gaugeSwiss Central Railway.[13]
The Mallet type developed and outgrew the original wheel arrangement, particularly in the US, also gaining tenders and often being simple expansion engines rather than compounds.[14] A handful of Mallets in both Switzerland and Java expanded to0-4-4-2T, to give support for enlarged water capacity. The Swiss design was not successful and was replaced in turn by a2-4-4-0T.[15]
Eritrean Railways used many 0-4-4-0Ts.[16][17] 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 twelve950 mm gauge Mallets as theFS R.440 [it] class. These were used on thePalermo-Corleone-San Carlo Railway [it] until the end of the 1920s, when they were relocated toItalian colonies inEritrea.
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