Provision of the axles

The provision of the axles of a railway vehicle (Locomotive, car or Coach) relates to the whole of the bodies ranging between the rails and the elastic suspension and constituting the train of bearing: wheels, rims, Axle X, axle boxes, bearings…
For the synthetic description of the number and provision of the axles (with if necessary the distinction between axles carrying and axles Driving S an engine), various conventions were adoptées.

simplest consists in indicating the axles on the basis of the former part of the engine: the first Chiffre indicates the number of former not motorized carrying axles, the second the number of driving axles, the third the number of posterior not motorized carrying axles. For example, engine 89 of Strasburg Rail Road (Pennsylvania) has a former carrying bogie and three motorized axles coupled by a rod, its notation will be thus “1-3-0”.
In the system defined by UIC (International union of the railroads) which uses figures for the carrying axles and of the letters for the driving axles, the notation of the same engine becomes “1C”.
In the Anglo-Saxon countries, the provision of the axles is expressed by the number of wheels according to the system Whyte , of the name of Frederick Methvan Whyte, engineer Dutch of the New York Central. In the English literature however, it is almost always indicated like the system White , and the two orthographies are regarded as equivalent. Consequently, in the case of the preceding example, the notation will be “2-6-0” or in the old denomination of the steam engines, “Mogul”. The addition of “T” capital letter indicates the non-attendance of the tender: it is then about a Engine-tender.

American traditional system

It is not rare to fall, in particular for the locomotive with vapor, on old American notations of the provision of the axles, often derived from machines historical, places or of famous episodes, or sometimes decided by a given company.

It is the case of the machines called Berkshire (place where the first machine of this type proved reliable by exceeding a Mikado) by the majority of the railroad companies and baptized on the other hand “Kanawha” by Nickel Road Punt, of the name of the river close to the processing site.

Another example is given by the machines which the New York Central called “Hudson” while everywhere else they were called “Baltic”, respecting a kind of Prussian primacy for a provision with three driving axles preceded and followed by a bogie with two axles (actually the Prussian engines were “2-6-2T” and not with tender separate).

Here a list of correspondences between the modern American system and the traditional system:

0-4-0 Furnace Coupled
0-6-0 Six Coupled
0-8-0 Eight Coupled (or Switcher)
0-10-0 Ten Coupled
0-10-2 Union
2-2-0 Individual Planet
2-2-2
2-4-0 To carry
2-4-2 Columbian
2-6-0 Mogul
2-6-2 Meadow
2-6-4 Adriatic
2-8-0 Consolidation
2-8-2 Mikado (shortened as Mike. McArthur in time of war)
2-8-4 Berkshire (also Lima or Kanawha)
2-10-0 Decapod
2-10-2 Santa Fe
2-10-4 Texas (or Colorado)
2-12-0 Centipede
4-2-0 Sixwheeler (or Jervis)
4-2-2 Bicycle
4-4-0 American (or Eightwheeler)
4-4-2 Atlantic
4-4-4 Jubilee
4-6-0 Tenwheeler
4-6-2 Pacific
4-6-4 Hudson (or Baltic)
4-8-0 Tewlvewheeler
4-8-2 Mohawk (or Mountain)
the 4-8-4 Niagara (also Confederation, Dixie, Montana, Pocono or Potomac among the most common names)
4-10-0 Mastodon
4-10-2 Southern Pacific
4-10-4 Overland
4-12-2 Union Pacific
6-2-0 Crampton
0-6-6-0 Erie
0-8-8-0 Angus
2-6-6-0 Virginian
2-6-6-6 Blue Ridge (more rarely Allegheny)
2-8-8-2 Chesapeake (or Cab Forward)
2-8-8-4 Yellowstoneu
4-4-4-4 Duplex
4-6-6-2 Cabforward
4-6-6-4 Challenger
4-8-8-4 Big-Servant boy
6-4-4-6 Pennsylvania
2-8-8-8-X Plywood (to 2 or 4 posterior not motorized wheels)

As example, the “Big Servant boy”, “4-8-8-4”, true monsters of the rails, used to tractor draw heavy trains of goods, aligned 4 former wheels (on two axles) carrying but not motor coaches, 16 driving wheels actuated by two groups of independent cylinders (from where division in two distinct digits) which dealt with 4 axles each one, and finally 4 nondriving carrying wheels.

System UIC

The most current machines currently are indicated according to system UIC by initials such as “Bo' Bo'” or “BoBoBo”.

Thus, the significance of the examples above is the following one:

each capital letter indicates the presence of a bogie (in this case 2 and 3 respectively)
“B” at the head means 2 driving axles in each bogie (in the same way the letter “C” would have meant 3 driving axles and the letter “D”, 4)
the absence of figure of the initials means the absence of former carrying axles. A notation such as “1Bo” indicates on the other hand the presence of an axle carrying in front of a bogie 2 driving axles.
the driving axles are motorized independently and can rotate (“O” lower-case). If they turn in group (the bogies which is directed to follow the way), one adds an apostrophe ““” to the end: “Bo' Bo””
if it is the carrying axle which is free and which can be directed freely to follow the way, one adds ““” after the figure: “1 ' B”
certain motor coaches can be made up of separate and independent half-cases: in this case one gathers the bogies between brackets. “(Bo' Bo”) (Bo' Bo')” a vehicle made up of two coupled elements indicates, each one with two bogies of two gathered driving axles.
if on the other hand the coupling between the half-cases is permanent, one employs the sign “+”: “2Co+2Co” would indicate one thus (hypothetical) indivisible vehicle but with a pivot in the center, 2 free axles and 3 driving axles for each group.

It should be specified however that currently the great majority of the engines are types “Bo' Bo'” and “Co' Co'”, and that the accent which indicates the regrouping is frequently omitted.

Other systems of classification

System AAR

Currently in the Anglo-Saxon countries (the United States and Canada), it is the system known as AAR ( Association off Americans Railroads ) which was adopted conventionally by the adherent railway companies of this association. system AAR constitutes a simplification of the international system UIC, of which it preserves the principle of using letters for the driving axles and of the figures for the carrying axles, however neglecting the symbols which in system UIC specify if the axles are motorized independently or free to turn and to be directed. Figures and letters are joined together in groups separated by a hyphen which indicates the regrouping of the axles out of bogies.

Some examples:

A1A-A1A : two bogies of three axles each one, which only the central axle is carrying;
B-B-B: three bogies of two axles each one, all engines;
DC: two bogies of three axles each one, all engines.

See too

Classification of the engines

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