Whyte notation

From Wikipedia, the free encyclopedia

A selection of early 20th century locomotive types according to their Whyte notation and their comparative size
Whyte notation from a handbook for railroad industry workers published in 1906[1]

The Whyte notation is a classification method for steam locomotives, and some internal combustion locomotives and electric locomotives, by wheel arrangement. It was devised by Frederick Methvan Whyte,[2] and came into use in the early twentieth century following a December 1900 editorial in American Engineer and Railroad Journal.

The notation was adopted and remains in use in North America and the United Kingdom to describe the wheel arrangements of steam locomotives, but for modern locomotives, multiple units and trams it has been supplanted by the UIC system in Europe and by the AAR system (essentially a simplification of the UIC system) in North America.

Structure of the system[edit]

Basic form[edit]

The notation in its basic form counts the number of leading wheels, then the number of driving wheels, and finally the number of trailing wheels, numbers being separated by dashes.[3] For example, a locomotive with two leading axles (four wheels) in front, then three driving axles (six wheels) and then one trailing axle (two wheels) is classified as a 4-6-2 locomotive, and is commonly known as a Pacific.

Denotion of other locomotives[edit]

Articulated locomotives[edit]

For articulated locomotives that have two wheelsets, such as Garratts, which are effectively two locomotives joined by a common boiler, each wheelset is denoted separately, with a plus sign (+) between them. Thus a "double Pacific" type Garratt is a 4-6-2+2-6-4. For Garratt locomotives, the plus sign is used even when there are no intermediate unpowered wheels, e.g. the LMS Garratt 2-6-0+0-6-2. This is because the two engine units are more than just power bogies. They are complete engines, carrying fuel and water tanks. The plus sign represents the bridge (carrying the boiler) that links the two engines.

Simpler articulated types, such as Mallets, have a jointed frame under a common boiler where there are no unpowered wheels between the sets of powered wheels. Typically, the forward frame is free to swing, whereas the rear frame is rigid with the boiler. Thus, a Union Pacific Big Boy is a 4-8-8-4; four leading wheels, one group of eight driving wheels, another group of eight driving wheels, and then four trailing wheels. Sometimes articulated locomotives of this type are denoted with a “+” between each driving wheels set (so in the previous case, the big boy would be a 4-8+8-4). This may have been developed to distinguish articulated and duplex arrangements; duplex arrangements would get a “-“ being rigid and articulated locomotives would get a “+” being flexible. However, given all the wheel arrangements for duplex locomotives have been mutually exclusive to them, it is usually considered unnecessary and thus another “-“ is usually used.

Triplex locomotives, and any theoretical larger ones, simply expand on basic articulated locomotives, for example, 2-8-8-8-2. In the case of the Belgium quadruplex, the arrangement is listed as 0-6-2+2-4-2-4-2+2-6-0.[4]

Duplex locomotives[edit]

For duplex locomotives, which have two sets of coupled driving wheels mounted rigidly on the same frame, the same method is used as for Mallet articulated locomotives – the amount of leading wheels are placed first, followed by the leading set of driving wheels, followed by the trailing set of driving wheels, followed by the trailing wheels, each number being separated by a hyphen.

Tank locomotives[edit]

A number of standard suffixes can be used to extend the Whyte notation for tank locomotives:[5]

Suffix Meaning Example
[No Suffix] Tender locomotive 0-6-0
T Side tank locomotive 0-6-2T
ST Saddle tank locomotive 0-4-0ST
WT Well tank locomotive 0-4-0WT
PT Pannier tank locomotive 0-6-0PT
C or CT Crane tank locomotive 0-6-2CT
IST Inverted saddle tank locomotive 0-4-2IST
T+T (or ST+T, WT+T, etc.) Tender-tank locomotive 0-4-0T+T

Other steam locomotives[edit]

Various other types of steam locomotive can be also denoted through suffixes:[5]

VB or VBT Vertical boilered locomotive 0-6-0VB
F Fireless locomotive 0-6-0F
CA Compressed air locomotive 0-6-0CA
R Railcar 0-4-4-0R
R or RT Rack locomotive 0-4-0RT

Internal combustion locomotives[edit]

The wheel arrangement of small diesel and petrol locomotives can be classified using the same notation as steam locomotives, e.g. 0-4-0, 0-6-0, 0-8-0. Where the axles are coupled by chains or shafts (rather than side rods) or are individually driven, the terms 4w (4-wheeled), 6w (6-wheeled) or 8w (8-wheeled) are generally used. For larger locomotives, the UIC classification is more commonly used.

Various suffixes are also used to denote the different types of internal combustion locomotives:[5]

Suffix Meaning Example
PM Petrol-mechanical locomotive 4wPM
PE Petrol-electric locomotive 0-6-0PE
D Diesel locomotive 6wD
DM Diesel–mechanical locomotive 8wDM
DE Diesel–electric locomotive 0-4-0DE
DH Diesel–hydraulic locomotive 0-6-0DH

Electric locomotives[edit]

The wheel arrangement of small electric locomotives can be denoted using this notation, like with internal combustion locomotives.

Suffixes used for Electric locomotives include:

Suffix Meaning Example
BE Battery-electric locomotive 4wBE
OE Overhead-lines electric locomotive 0-8-0OE
RE Third rail electric locomotive 4wRE

Wheel arrangement names[edit]

In American (and to a lesser extent British) practice, most wheel arrangements in common use were given names, sometimes from the name of the first such locomotive built. For example, the 2-2-0 type arrangement is named Planet, after the 1830 locomotive on which it was first used. (This naming convention is similar to the naming of warship classes.)

Common wheel arrangements[edit]

The most common wheel arrangements are listed below. In the diagrams, the front of the locomotive is to the left.

(locomotive front is to the left)
Whyte classification Name No. of units produced
Non-articulated locomotives
WheelArrangement 0-2-2.svg 0-2-2 Northumbrian
WheelArrangement 2-2-0.svg 2-2-0 Planet
WheelArrangement 2-2-2.svg 2-2-2 Patentee, Single,[2] Jenny Lind
WheelArrangement 2-2-4.svg 2-2-4 Aerolite
WheelArrangement 4-2-0.svg 4-2-0 Jervis[6]
WheelArrangement 4-2-2.svg 4-2-2 Bicycle, Iron Duke, Single
WheelArrangement 4-2-4.svg 4-2-4 Huntington
WheelArrangement 6-2-0.svg 6-2-0 Crampton[7]
WheelArrangement 0-4-0.svg 0-4-0 Four-coupled
WheelArrangement 0-4-4.svg 0-4-0+4 Four-coupled as used on railmotors
WheelArrangement 0-4-2.svg 0-4-2 Olomana
WheelArrangement 0-4-4.svg 0-4-4 Forney[1]
WheelArrangement 2-4-0.svg 2-4-0 Porter, 'Old English'[8]
WheelArrangement 2-4-2.svg 2-4-2 Columbia[1]
WheelArrangement 2-4-4.svg 2-4-4 Boston
WheelArrangement 4-4-0.svg 4-4-0 American,[1][9] eight-wheeler
WheelArrangement 4-4-2.svg 4-4-2 Atlantic[1][10]
WheelArrangement 4-4-4.svg 4-4-4 Reading, Jubilee (Canada)[11]
WheelArrangement 0-6-0.svg 0-3-0 (one driving wheel per axle; used on Patiala State Monorail Trainways and also on the Listowel and Ballybunion Railway)
WheelArrangement 0-6-0.svg 0-6-0 Six-coupled,[1] Bourbonnais (France)
WheelArrangement 0-6-2.svg 0-6-2 Branchliner, Webb
WheelArrangement 0-6-4.svg 0-6-4 Forney six-coupled[1]
WheelArrangement 0-6-6.svg 0-6-6
WheelArrangement 2-6-0.svg 2-6-0 Mogul[1][12] 11,000
WheelArrangement 2-6-2.svg 2-6-2 Prairie[1][2]
WheelArrangement 2-6-4.svg 2-6-4 Adriatic
WheelArrangement 2-6-6.svg 2-6-6 Suburban
WheelArrangement 4-6-0.svg 4-6-0 Ten-wheeler[1][13] (not Britain)[14]
WheelArrangement 4-6-2.svg 4-6-2 Pacific[1][2][15][16] 6,800
WheelArrangement 4-6-4.svg 4-6-4 Hudson,[17] Baltic[2]
4-6-6 Use on the Boston and Albany Railroad.[18]
WheelArrangement 0-8-0.svg 0-8-0 Eight-coupled[1]
WheelArrangement 0-8-2.svg 0-8-2 River Irt
WheelArrangement 0-8-4.svg 0-8-4 London
WheelArrangement 2-8-0.svg 2-8-0 Consolidation[1][2][19] 35,000
WheelArrangement 2-8-2.svg 2-8-2 Mikado,[1][2] Mike, MacArthur[20][21]
WheelArrangement 2-8-4.svg 2-8-4 Berkshire, Kanawha[22][23]
WheelArrangement 2-8-6.svg 2-8-6 Used only on four Mason Bogie locomotives
WheelArrangement 4-8-0.svg 4-8-0 Twelve Wheeler[1][24]
WheelArrangement 4-8-2.svg 4-8-2 Mountain,[2][25] Mohawk (NYC)[26]
WheelArrangement 4-8-4.svg 4-8-4 Northern, Niagara, Confederation, Dixie, Greenbrier, Pocono, Potomac, Heavy Mountain (Atchison, Topeka, and Santa Fe), Golden State (Southern Pacific),[27] Western, Laurentian (Delaware & Hudson Railroad), General, Wyoming (Lehigh Valley[28]), Governor, Big Apple, GS Series "Daylight" (Southern Pacific)[27]
WheelArrangement 4-8-6.svg 4-8-6 Proposed by Lima, never built
WheelArrangement 6-8-6.svg 6-8-6 Turbine, only used on the PRR S2 Steam Turbine 1
WheelArrangement 0-10-0.svg 0-10-0 Ten-coupled,[1][29] (rarely) Decapod
WheelArrangement 0-10-2.svg 0-10-2 Union[29]
WheelArrangement 2-10-0.svg 2-10-0 Decapod,[1][30] Russian Decapod
WheelArrangement 2-10-2.svg 2-10-2 Santa Fe,[1] Central, Decapod (only on the Southern Pacific)
WheelArrangement 2-10-4.svg 2-10-4 Texas, Colorado (CB&Q), Selkirk (Canada)[31]
WheelArrangement 4-10-0.svg 4-10-0 Mastodon[1][24]
WheelArrangement 4-10-2.svg 4-10-2 Reid Tenwheeler,[32][33] Southern Pacific, Overland[34]
WheelArrangement 0-12-0.svg 0-12-0 Twelve-coupled
WheelArrangement 2-12-0.svg 2-12-0 Centipede[1]
WheelArrangement 2-12-2.svg 2-12-2 Javanic 30
WheelArrangement 2-12-4.svg 2-12-4 Bulgaria 20
2-12-6 Proposed by Lima, never built
WheelArrangement 4-12-2.svg 4-12-2 Union Pacific[35] 88
WheelArrangement 4-14-4.svg 4-14-4 AA20[36] 1
Duplex locomotives
0-2-2-0 Used on the Mount Washington Cog Railway
WheelArrangement 4-4-4-4.svg 4-4-4-4 (PRR T1)[37] 53
WheelArrangement 6-4-4-6.svg 6-4-4-6 (PRR S1)[38] 1
WheelArrangement 4-4-6-4.svg 4-4-6-4 (PRR Q2)[39] 26
WheelArrangement 4-6-4-4.svg 4-6-4-4 (PRR Q1) 1
Articulated locomotives (simple and compound)
WheelArrangement 0-4-4-0.svg 0-4-4-0 Four Coupled Mallet
WheelArrangement 2-4-0.svg WheelArrangement 0-4-0.svg 2-4-4-0 Vivarais 5
WheelArrangement 0-4-0.svg WheelArrangement 0-4-2.svg 0-4-4-2 Swiss
WheelArrangement 2-4-4-2.svg 2-4-4-2 Skookum
4-4-6-2 AT&SF[40] 2
WheelArrangement 0-6-6-0.svg 0-6-6-0 Erie
WheelArrangement 2-6-6-0.svg 2-6-6-0 Mogul Mallet
WheelArrangement 2-6-6-2.svg 2-6-6-2 Chesapeake 1,300
WheelArrangement 2-6-6-4.svg 2-6-6-4 Adriatic Mallet 60
WheelArrangement 2-6-6-6.svg 2-6-6-6 Allegheny,[41] Blue Ridge 68
WheelArrangement 4-6-6-2.svg 4-6-6-2 (Southern Pacific class AM-2)[42]
WheelArrangement 4-6-6-4.svg 4-6-6-4 Challenger[43] 252
WheelArrangement 2-6-8-0.svg 2-6-8-0 (Southern Railway, Great Northern Railway)[44] 39
WheelArrangement 0-8-8-0.svg 0-8-8-0 Angus
WheelArrangement 2-8-8-0.svg 2-8-8-0 Bull Moose
WheelArrangement 2-8-8-2.svg 2-8-8-2 Mikado Mallet 222
WheelArrangement 2-8-8-4.svg 2-8-8-4 Yellowstone[45] 78
WheelArrangement 4-8-8-2.svg 4-8-8-2 Mountain Mallet 195
WheelArrangement 4-8-8-4.svg 4-8-8-4 Big Boy[46] 25[47]
WheelArrangement 2-10-10-2.svg 2-10-10-2 (Santa Fe and Virginian railroads)[44] 20
WheelArrangement 2-8-8-8-2.svg 2-8-8-8-2 Triplex (Erie RR) 3
WheelArrangement 2-8-8-8-4.svg 2-8-8-8-4 Triplex (Virginian RR)[48] 1
Garratt articulated locomotives
WheelArrangement 0-4-0+0-4-0.svg 0-4-0+0-4-0 Double Four Coupled
WheelArrangement 0-6-6-0.svg 0-6-0+0-6-0 Double Six Coupled
WheelArrangement 2-4-4-2.svg 2-4-0+0-4-2 Double Porter
WheelArrangement 2-4-2+2-4-2.svg 2-4-2+2-4-2 Double Columbia
WheelArrangement 2-6-6-2.svg 2-6-0+0-6-2 Double Mogul
WheelArrangement 2-6-2+2-6-2.svg 2-6-2+2-6-2 Double Prairie
WheelArrangement 2-8-8-2.svg 2-8-0+0-8-2 Double Consolidation
WheelArrangement 2-8-2+2-8-2.svg 2-8-2+2-8-2 Double Mikado
WheelArrangement 4-4-2+2-4-4.svg 4-4-2+2-4-4 Double Atlantic
WheelArrangement 4-6-6-4.svg 4-6-0+0-6-4 Mogyana
WheelArrangement 4-6-2+2-6-4.svg 4-6-2+2-6-4 Double Pacific
WheelArrangement 4-6-4+4-6-4.svg 4-6-4+4-6-4 Double Baltic, Double Hudson
WheelArrangement 4-8-8-4.svg 4-8-0+0-8-4 Double Mastodon
WheelArrangement 4-8-2+2-8-4.svg 4-8-2+2-8-4 Double Mountain
WheelArrangement 4-8-4+4-8-4.svg 4-8-4+4-8-4 Double Northern

See also[edit]


  1. ^ a b c d e f g h i j k l m n o p q r s t Colvin, Fred H. (1906). The railroad pocket-book: a quick reference cyclopedia of railroad information. New York, Derry-Collard; London, Locomotive Publishing Company (US-UK co-edition). p. L‑9.
  2. ^ a b c d e f g h "Steam Locomotive Glossary". Railway Technical Web Pages. 28 June 2007. Archived from the original on 28 January 2008. Retrieved 8 February 2008.
  3. ^ Thompson, Keith (1 May 2006). "Builder's plates: A locomotive's birth certificate". Kalmbach Publishing. Archived from the original on 22 November 2008. Retrieved 8 February 2008.
  4. ^ "The Franco-Crosti Boiler System".
  5. ^ a b c Industrial Locomotives: including preserved and minor railway locomotives. Vol. 17EL. Melton Mowbray: Industrial Railway Society. 2015. ISBN 978 1 901556 88 9.
  6. ^ White, John H. Jr. (1968). A History of the American Locomotive - Its Development: 1830-1880. New York: Dover Publications. ISBN 0-486-23818-0., p. 33.
  7. ^ Adams, Bob (December 1968). "The Crampton Type Locomotive on the Camden & Amboy Railroad". NMRA Bulletin. National Model Railroad Association.
  8. ^ Ellis, C Hamilton, Some Classic Locomotives, Allen & Unwin, 1949.173 p.
  9. ^ White (1968), p. 46.
  10. ^ Marsden, Richard (2008). "The LNER 4-4-2 Atlantic Locomotives". The London & North Eastern Railway (LNER) Encyclopedia. Archived from the original on 13 February 2008. Retrieved 8 February 2008.
  11. ^ "Canadian Pacific Railway No. 2929". Steamtown NHS Special History Study. United States National Park Service. 14 February 2002. Archived from the original on 19 May 2007. Retrieved 8 February 2008.
  12. ^ White (1968), p 62-65.
  13. ^ White (1968), p. 57.
  14. ^ Marsden, Richard (2008). "LNER 4-6-0 Locomotives". The London & North Eastern Railway (LNER) Encyclopedia. Archived from the original on 13 February 2008. Retrieved 8 February 2008.
  15. ^ Marsden, Richard (2008). "LNER 4-6-2 Pacific Locomotives". The London & North Eastern Railway (LNER) Encyclopedia. Archived from the original on 25 February 2008. Retrieved 8 February 2008.
  16. ^ "Pacifics". SteamLocomotive.com. Archived from the original on 25 January 2008. Retrieved 8 February 2008.
  17. ^ "Hudsons". SteamLocomotive.com. Archived from the original on 27 January 2008. Retrieved 8 February 2008.
  18. ^ "Boston & Albany 4-6-6 Locomotives in the USA". steamlocomotive.com. Retrieved 21 April 2021.
  19. ^ White (1968), p. 65.
  20. ^ "Glossary of Common Railroad Terms: M". Kalmbach Publishing. Retrieved 8 February 2008.
  21. ^ "The Mikado Type Locomotive". SteamLocomotive.com. Archived from the original on 12 June 2013. Retrieved 8 February 2008.
  22. ^ Farrell, Jack W. (1989). North American steam locomotives: The Berkshire and Texas types. Pacific Fast Mail. Edmonds, WA. ISBN 0-915713-15-2.
  23. ^ "Berkshires & Kanawhas". SteamLocomotive.com. Archived from the original on 26 January 2008. Retrieved 8 February 2008.
  24. ^ a b "Locomotives: Whyte's Notation". Locomotive Cyclopedia of American Practice. Simmons-Boardman Publishing Corporation. 1922. pp. 106–107.
  25. ^ "Mountains". SteamLocomotive.com. Archived from the original on 30 January 2008. Retrieved 8 February 2008.
  26. ^ Taylor, Frank (January 1941). "New York Central Dual-service Mohawk". Model Railroader. Kalmbach Publishing.
  27. ^ a b "Northerns". SteamLocomotive.com. Archived from the original on 12 February 2008. Retrieved 8 February 2008.
  28. ^ "Lehigh Valley Wyomings". Archived from the original on 13 August 2010. Retrieved 25 May 2010.
  29. ^ a b Carlson, Neil (3 July 2006). "Steam locomotive profile: 0-10-0". Classic Trains. Kalmbach Publishing. Archived from the original on 29 September 2007. Retrieved 8 February 2008.
  30. ^ "Glossary of Common Railroad Terms: D". Kalmbach Publishing. Archived from the original on 1 January 2007. Retrieved 8 February 2008.
  31. ^ "The Texas Type Locomotive". SteamLocomotive.com. Archived from the original on 25 February 2008. Retrieved 8 February 2008.
  32. ^ Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 10–11, 31. ISBN 0869772112.
  33. ^ Holland, D.F. (1971). Steam Locomotives of the South African Railways. Vol. 1: 1859–1910 (1st ed.). Newton Abbott, England: David & Charles. pp. 92–95, 123–124, 134–135. ISBN 978-0-7153-5382-0.
  34. ^ Westing, Frederick (April 1954). "Baldwin's barnstorming behemoth". Trains.
  35. ^ Westcott, Linn H. (1960). Model Railroader Cyclopedia - Volume 1: Steam Locomotives. Kalmbach Books. ISBN 0-89024-001-9.
  36. ^ "Russian Reforms". 6 October 2001. Archived from the original on 18 October 2010. Retrieved 8 February 2008.
  37. ^ Russ, David (July 1943). "Riding the Pennsy T1". Trains. Kalmbach Publishing.
  38. ^ Morgan, David P. (May 1965). "They called her the big engine". Trains. Kalmbach Publishing.
  39. ^ Herring, S. E. & Morgan, David P. (June 1966). "Instead of a 4-10-4". Trains. Kalmbach Publishing.
  40. ^ "The Jointed-Boiler Locomotives," Trains magazine, February 1945
  41. ^ "The Allegheny Type Locomotive". SteamLocomotive.com. Archived from the original on 27 January 2008. Retrieved 8 February 2008.
  42. ^ Diebert, Timothy S. & Strapac, Joseph A. (1987). Southern Pacific Company Steam Locomotive Conpendium. Shade Tree Books. ISBN 0-930742-12-5.
  43. ^ "The Challenger Type Locomotive". SteamLocomotive.com. Archived from the original on 1 December 2005. Retrieved 8 February 2008.
  44. ^ a b Carlson, Neil (15 June 2006). "Steam locomotive profile: 2-8-8-2". Classic Trains. Kalmbach Publishing. Archived from the original on 16 November 2008. Retrieved 8 February 2008.
  45. ^ "The Yellowstone Type Locomotive". SteamLocomotive.com. Archived from the original on 3 February 2003. Retrieved 8 February 2008.
  46. ^ "Union Pacific Big Boys". SteamLocomotive.com. Archived from the original on 22 September 2009. Retrieved 8 February 2008.
  47. ^ "Union Pacific Big Boy: The rebirth of a legend". Trains. 23 August 2013. Archived from the original on 12 July 2015. Retrieved 8 November 2016.
  48. ^ "Virginian Class XA Locomotives". SteamLocomotive.com. Archived from the original on 12 January 2008. Retrieved 8 February 2008.

Further reading[edit]

External links[edit]

In the various names above of a 4-8-4, omitted was the letters "F E F" which simply means: four eight four.