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Whyte notation
*** Shopping-Tip: Whyte notation
Image:Locotypes.gif thumb|200px|A selection of early 20th century locomotive types according to their Whyte notation and their comparative size
The '''Whyte notation''' for classifying
steam locomotives by
wheel arrangement was devised by
Frederick Methvan Whyte and came into use in the early
20th century. Whyte's system counts the number of
leading wheels, then the number of
driving wheels, and finally the number of
trailing wheels, this being the common pattern of the conventional steam locomotive.
Thus, a locomotive with two leading
axles (and thus four wheels) in front, then three driving axles (six wheels) and followed by one trailing axle (two wheels) is classified as a
4-6-2.
It's important to stress that wheels, not axles, are what is counted in this system. Other classification schemes, like
UIC classification, count axles.
The system had to be extended with the advent of
articulated locomotives. The scheme generally adopted is that
locomotives such as
Garratts, where there are, in effect, two separate locomotives joined by a common
boiler, are classified by using a plus sign in between the arrangements of each engine. Thus, a 'double Pacific' type Garratt is a 4-6-2+2-6-4.
Simpler articulated types such as
Mallet (locomotive) Mallets, where there are no unpowered axles in between powered axles, are just written by adding extra numbers in the middle; each number represents a grouping of wheels. Thus a
Union Pacific Big Boy Big Boy is written under this modified Whyte notation as a 4-8-8-4; there are two leading axles, one group of four driving axles, another group of four driving axles, and then two trailing axles.
In addition the suffix 'T' is often used to indicate a
tank locomotive; otherwise, a
tender locomotive is assumed. In British practice, this is sometimes extended to indicate what ''type'' of tank locomotive. When this is done, plain T means
side tank, ST
saddle tank, PT
pannier tank and WT
well tank. Where a 'T' suffix is followed by '+T', this indicates a tank locomotive that has a tender for additional coal or water capacity.
The limitations of the Whyte system for classifying locomotives that did not fit the standard steam locomotive pattern led to the design of other forms of classification. Most commonly used in Europe is the
UIC classification scheme, based on
Germany German practice, which can more completely define the exact layout of a locomotive.
In
United States American (and to a lesser extent
United Kingdom British) practice, most wheel arrangements in common use were given names.
Here is a list of the most common wheel arrangements: in the illustration, which should be read left to right, with the front of the locomotive to the left, small o is a carrying axle, and a big O is a driving axle.
{| class="wikitable"
!align=left|Arrangement!!align=left|Whyte Classification!!align=left|Name
|-
|colspan="3"|
|-
!colspan="3"|''Non-Articulated Locomotives''
|-
|colspan="3"|
|-
|Oo||
0-2-2||Northumbrian
|-
|oO||
2-2-0||Planet
|-
|oOo||
2-2-2||Single, Jenny Lind
|-
|oOoo||
2-2-4||
|-
|ooO||
4-2-0||Jervis
|-
|ooOo||
4-2-2||Bicycle
|-
|ooOoo||
4-2-4 (locomotive) 4-2-4||
|-
|oooO||
6-2-0||Crampton
|-
|colspan="3"|
|-
|OO||
0-4-0||Four-Coupled
|-
|OOo||
0-4-2||
|-
|OOoo||
0-4-4||Forney
|-
|oOO||
2-4-0||Porter
|-
|oOOo||
2-4-2||Columbia
|-
|oOOoo||
2-4-4||
|-
|ooOO||
4-4-0||American, Eight-wheeler
|-
|ooOOo||
4-4-2 (locomotive) 4-4-2||Atlantic
|-
|ooOOoo||
4-4-4||Reading, Jubilee (Canada)
|-
|colspan="3"|
|-
|OOO||
0-6-0||Six-Coupled
|-
|OOOo||
0-6-2||
|-
|OOOoo||
0-6-4||
|-
|oOOO||
2-6-0||Mogul
|-
|oOOOo||
2-6-2||Prairie
|-
|oOOOoo||
2-6-4||Adriatic
|-
|oOOOooo||
2-6-6||
|-
|ooOOO||
4-6-0||Ten-Wheeler (not Britain)
|-
|ooOOOo||
4-6-2||Pacific
|-
|ooOOOoo||
4-6-4||Hudson, Baltic
|-
|colspan="3"|
|-
|OOOO||
0-8-0||Eight-Coupled
|-
|OOOOo||
0-8-2||
|-
|oOOOO||
2-8-0||Consolidation
|-
|oOOOOo||
2-8-2||Mikado, Mike, MacArthur
|-
|oOOOOoo||
2-8-4||Berkshire, Kanawha
|-
|oOOOOooo||
2-8-6||''Used only on four
Mason Bogie locomotives''
|-
|ooOOOO||
4-8-0||Mastodon, Twelve-Wheeler
|-
|ooOOOOo||
4-8-2||Mountain, Mohawk
|-
|ooOOOOoo||
4-8-4.html">Big Apple (4-8-4)
Big Apple
|-
|ooOOOOooo||
4-8-6.html">Lima Locomotive Works
Lima, never built''
|-
|oooOOOOooo||
6-8-6||(
PRR S2 steam turbine locomotive)
|-
|colspan="3"|
|-
|OOOOO||
0-10-0||Ten-Coupled, (rarely) Decapod
|-
|OOOOOo||
0-10-2||Union
|-
|oOOOOO||
2-10-0||Decapod
|-
|oOOOOOo||
2-10-2||Santa Fe, Central, Decapod (only on the Southern Pacific)
|-
|oOOOOOoo||
2-10-4||Texas,
Colorado (
CB&Q), Selkirk (Canada)
|-
|ooOOOOO||
4-10-0||Mastodon, Gobernador (in honor of ''
El Gobernador'')
|-
|ooOOOOOo||
4-10-2||
Southern Pacific, Overland
|-
|colspan="3"|
|-
|OOOOOO||
0-12-0||Twelve-Coupled
|-
|oOOOOOO||
2-12-0||Centipede
|-
|oOOOOOOo||
2-12-2||Javanic
|-
|oOOOOOOoo||
2-12-4||
|-
|ooOOOOOOo||
4-12-2||
Union Pacific
|-
|colspan="3"|
|-
|ooOOOOOOOoo||
4-14-4|| AA20
|-
|colspan="3"|
|-
!colspan="3"|''
Duplex locomotive Duplex Locomotives''
|-
|colspan="3"|
|-
|ooOO OOoo||
4-4-4-4||(
PRR T1)
|-
|oooOO OOooo||
6-4-4-6||(
PRR S1)
|-
|ooOO OOOoo||
4-4-6-4||(
PRR Q2)
|-
|ooOOO OOoo||
4-6-4-4||(
PRR Q1)
|-
|colspan="3"|
|-
!colspan="3"|''
Mallet (locomotive) Mallet and Simple Articulated Locomotives''
|-
|colspan="3"|
|-
|OO-OO||
0-4-4-0||
|-
|o-OO-OO-o||
2-4-4-2||
|-
|OOO-OOO||
0-6-6-0||Erie
|-
|oOOO-OOO||
2-6-6-0||Denver & Salt Lake
|-
|oOOO-OOOo||
2-6-6-2||
|-
|oOOO-OOOoo||
2-6-6-4||Norfolk & Western
|-
|oOOO-OOOooo||
2-6-6-6||Allegheny, Blue Ridge
|-
|ooOOO-OOOo||
4-6-6-2||(
Southern Pacific class MM-2)
|-
|ooOOO-OOOoo||
4-6-6-4||Challenger
|-
|colspan="3"|
|-
|oOOO-OOOO||
2-6-8-0||(Southern Railway, Great Northern Railway)
|-
|colspan="3"|
|-
|OOOO-OOOO||
0-8-8-0||Angus
|-
|oOOOO-OOOO||
2-8-8-0||Bull Moose
|-
|oOOOO-OOOOo||
2-8-8-2||Chesapeake
|-
|oOOOO-OOOOoo||
2-8-8-4||Yellowstone
|-
|ooOOOO-OOOOo||
4-8-8-2||(Southern Pacific cab forward)
|-
|ooOOOO-OOOOoo||
4-8-8-4||Big Boy
|-
|colspan="3"|
|-
|oOOOOO-OOOOOo||
2-10-10-2||(Santa Fe and Virginian railroads)
|-
|colspan="3"|
|-
|oOOOO-OOOO-OOOO-o||
2-8-8-8-2||Triplex (Erie RR)
|-
|oOOOO-OOOO-OOOO-oo||
2-8-8-8-4||Triplex
|}
''Garratts'' are almost always two identical locomotive frames back-to-back, and are thus called ''Double Pacifics'', ''Double Northerns'' etc.
See also
*
Wheel arrangement
*
UIC classification
*
:Category:Locomotives by wheel arrangement
Category:Locomotives 1 Whyte notation
Category:Classification systems
*** Shopping-Tip: Whyte notation
