Wheel arrangement
Encyclopedia
In rail transport
, a wheel arrangement is a system of classifying the way in which wheels are distributed beneath a locomotive
.. Several notations exist to describe the wheel assemblies of a locomotive
by type, position, and connections, with the adopted notations varying by country. Within a given country, different notations may also be employed for different kinds of locomotives, such as steam
, electric
, and diesel
powered.
Especially in steam days, wheel arrangement was an important attribute of a locomotive because there were many different types of layout adopted, each wheel being optimised for a different use (often with only some being actually "driven"). Modern diesel and electric locomotives are much more uniform, usually with all axles driven.
(based on counting the wheels), the AAR wheel arrangement
notation (based on counting either the axles or the bogie
s), and the UIC classification of locomotive axle arrangements
(based on counting either the axles or the bogies).
Whyte notation is generally used for steam locomotive
s throughout the United States
, Canada
, the United Kingdom
and Ireland
. For diesels and electrics, North America
uses the AAR wheel arrangement scheme while British practice uses a slightly simplified form of the European UIC classification scheme (except for small diesel shunters, where Whyte notation is used).
In mainland Europe
, the UIC classification scheme is generally used for all locomotive types including steam, with some exceptions. In France
, the UIC classification is used for diesels and electrics while a scheme similar to the Whyte notation, but counting axles insteads of wheels, is used for steam locomotives. Notably, Switzerland
had its own separate notation system until 1989, with the Swiss locomotive and railcar classification now only retained for its narrow gauge railways.
Rail transport
Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...
, a wheel arrangement is a system of classifying the way in which wheels are distributed beneath a locomotive
Locomotive
A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...
.. Several notations exist to describe the wheel assemblies of a locomotive
Locomotive
A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...
by type, position, and connections, with the adopted notations varying by country. Within a given country, different notations may also be employed for different kinds of locomotives, such as steam
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
, electric
Electric locomotive
An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...
, and diesel
Diesel locomotive
A diesel locomotive is a type of railroad locomotive in which the prime mover is a diesel engine, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel...
powered.
Especially in steam days, wheel arrangement was an important attribute of a locomotive because there were many different types of layout adopted, each wheel being optimised for a different use (often with only some being actually "driven"). Modern diesel and electric locomotives are much more uniform, usually with all axles driven.
Major Notation Schemes
The main notations are the Whyte notationWhyte notation
The Whyte notation for classifying steam locomotives by wheel arrangement was devised by Frederick Methvan Whyte and came into use in the early twentieth century encouraged by an editorial in American Engineer and Railroad Journal...
(based on counting the wheels), the AAR wheel arrangement
AAR wheel arrangement
The AAR wheel arrangement system is a method of classifying locomotive wheel arrangements that was developed by the Association of American Railroads. It is essentially a simplification of the European UIC classification, and it is widely used in North America to describe diesel and electric...
notation (based on counting either the axles or the bogie
Bogie
A bogie is a wheeled wagon or trolley. In mechanics terms, a bogie is a chassis or framework carrying wheels, attached to a vehicle. It can be fixed in place, as on a cargo truck, mounted on a swivel, as on a railway carriage/car or locomotive, or sprung as in the suspension of a caterpillar...
s), and the UIC classification of locomotive axle arrangements
UIC classification of locomotive axle arrangements
The UIC classification of locomotive axle arrangements describes the wheel arrangement of locomotives, multiple units and trams. It is set out in the International Union of Railways "Leaflet 650 - Standard designation of axle arrangement on locomotives and multiple-unit sets". It is used in much...
(based on counting either the axles or the bogies).
Whyte notation is generally used for steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
s throughout the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
and Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
. For diesels and electrics, North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
uses the AAR wheel arrangement scheme while British practice uses a slightly simplified form of the European UIC classification scheme (except for small diesel shunters, where Whyte notation is used).
In mainland Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, the UIC classification scheme is generally used for all locomotive types including steam, with some exceptions. In France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, the UIC classification is used for diesels and electrics while a scheme similar to the Whyte notation, but counting axles insteads of wheels, is used for steam locomotives. Notably, Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
had its own separate notation system until 1989, with the Swiss locomotive and railcar classification now only retained for its narrow gauge railways.
- AAR wheel arrangementAAR wheel arrangementThe AAR wheel arrangement system is a method of classifying locomotive wheel arrangements that was developed by the Association of American Railroads. It is essentially a simplification of the European UIC classification, and it is widely used in North America to describe diesel and electric...
- Used largely throughout the US and Canada for diesel and electric locomotives. - UIC classification - Used in mainland Europe for all locomotive types. Used in the UK for electric and large diesel locomotives.
- Whyte notationWhyte notationThe Whyte notation for classifying steam locomotives by wheel arrangement was devised by Frederick Methvan Whyte and came into use in the early twentieth century encouraged by an editorial in American Engineer and Railroad Journal...
- Used in North America, the UK and Ireland for steam locomotives, and for shunters (US: switchers) in the UK.