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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, and came into use in the early twentieth century following a December 1900 editorial in American Engineer and Railroad Journal.
Under the Whyte notation for the classification of steam locomotives, 0-4-0 represents one of the simplest possible types, that with two axles and four coupled wheels, all of which are driven. The wheels on the earliest four-coupled locomotives were connected by a single gear wheel, but from 1825 the wheels were usually connected with coupling rods to form a single driven set.
In rail transport, a wheel arrangement or wheel configuration is a system of classifying the way in which wheels are distributed under 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.
On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons. On a conventional, non-articulated locomotive, the driving wheels are all coupled together with side rods ; normally one pair is directly driven by the main rod which is connected to the end of the piston rod; power is transmitted to the others through the side rods.
Under the Whyte notation for the classification of steam locomotives, 4-2-0 represents the wheel arrangement of four leading wheels on two axles, two powered driving wheels on one axle and no trailing wheels. This type of locomotive is often called a Jervis type, the name of the original designer.
Under the Whyte notation for the classification of steam locomotives, 2-2-0 represents the wheel arrangement of two leading wheels on one axle, two powered driving wheels on one axle, and no trailing wheels. This configuration, which became very popular during the 1830s, was commonly called the Planet type after the first locomotive, Robert Stephenson's Planet of 1830.
The AAR wheel arrangement system is a method of classifying locomotive wheel arrangements that was developed by the Association of American Railroads. Essentially a simplification of the European UIC classification, it is widely used in North America to describe diesel and electric locomotives. It is not used for steam locomotives, which use the Whyte notation instead.
Under the Whyte notation for the classification of steam locomotives, 4-2-2 represents the wheel arrangement of four leading wheels on two axles, two powered driving wheels on one axle, and two trailing wheels on one axle.
Under the Whyte notation for the classification of steam locomotives by wheel arrangement, 2-4-4 is a steam locomotive with two unpowered leading wheels followed by four powered driving wheels and four unpowered trailing wheels. The wheel arrangement was only used for tank locomotives.
On a steam locomotive, a trailing wheel or trailing axle is generally an unpowered wheel or axle (wheelset) located behind the driving wheels. The axle of the trailing wheels is usually located in a trailing truck. On some large locomotives, a booster engine was mounted on the trailing truck to provide extra tractive effort when starting a heavy train and at low speeds on gradients.
Co-Co is the wheel arrangement for diesel and electric locomotives with two six-wheeled bogies with all axles powered, with a separate traction motor per axle. The equivalent UIC classification (Europe) for this arrangement is Co′Co′, or C-C for AAR.
B-B and Bo-Bo are the Association of American Railroads (AAR) and British classifications of wheel arrangement for railway locomotives with four axles in two individual bogies. They are equivalent to the B′B′ and Bo′Bo′ classifications in the UIC system. The arrangement of two, two-axled, bogies is a common wheel arrangement for modern electric and diesel locomotives.
The Pennsylvania Railroad's class R1 comprised a single prototype electric locomotive constructed in 1934 by the Baldwin Locomotive Works of Philadelphia, Pennsylvania, US, with the electrical equipment by Westinghouse.
Under the Whyte notation for the classification of steam locomotives, 0-8-4 represents the wheel arrangement of no leading wheels, eight powered and coupled driving wheels on four axles, and four trailing wheels on two axles.
Under the Whyte notation for the classification of steam locomotives by wheel arrangement, a 4-6-2+2-6-4 is a Garratt or Union Garratt articulated locomotive using a pair of 4-6-2 engine units back to back, with the boiler and cab suspended between them. The 4-6-2 wheel arrangement of each engine unit has four leading wheels on two axles, usually in a leading bogie, six powered and coupled driving wheels on three axles, and two trailing wheels on one axle, usually in a trailing truck.
Co-Bo or Co′Bo′ is a wheel arrangement in the UIC classification system for railway locomotives. It features two uncoupled bogies. The "Co" bogie has three driven axles and the "Bo" bogie has two.
Under the French classification system for locomotive wheel arrangements, the system is slightly different for steam and electric/diesel vehicles.
The leading wheel or leading axle or pilot wheel of a steam locomotive is an unpowered wheel or axle located in front of the driving wheels. The axle or axles of the leading wheels are normally located on a leading truck. Leading wheels are used to help the locomotive negotiate curves and to support the front portion of the boiler.
The Swiss locomotive class Ae 4/6 was a class of electric locomotives. They were intended as a powerful locomotive for the steep gradients of the Gotthard Railway, but smaller than the huge 'double locomotives' which had previously been tested there. They were built from 1941, during World War II, and although Switzerland remained neutral through this, material shortages led to some quality problems with these locomotives.
Rigid-framed electric locomotives were some of the first generations of electric locomotive design. When these began the traction motors of these early locomotives, particularly with AC motors, were too large and heavy to be mounted directly to the axles and so were carried on the frame. One of the initial simplest wheel arrangements for a mainline electric locomotive, from around 1900, was the 1′C1′ arrangement, in UIC classification.
References
- ↑ The Railway Data File. Leicester: Silverdale, 2000. p. 52. ISBN 1-85605-499-3.
- ↑ Peck C.B., Locomotive cyclopedia of American practice, 1950-52, Association of American Railroads Mechanical Division, Simmons-Boardman Pub. Co., 1950, p. 449.
- ↑ Kalla-Bishop P.M. & Greggio, Luciano, Steam Locomotives, Crescent, 1985, p. 226.
- 1 2 3 IRS 60650 Railway Application - Rolling Stock - Standard designation of axle arrangement on locomotives and multiple-unit sets. Paris, France: International union of railways. 2021. ISBN 9782746125209 . Retrieved 23 October 2021.
