A wheelset is a pair of railroad vehicle

wheels A wheel is a rotating component (typically circular in shape) that is intended to turn on an axle bearing. The wheel is one of the key components of the wheel and axle which is one of the six simple machines. Wheels, in conjunction with axl ...

mounted rigidly on an

axle An axle or axletree is a central shaft for a rotation, rotating wheel and axle, wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In ...

. Wheelsets are often mounted in a

bogie A bogie ( ) (or truck in North American English) comprises two or more Wheelset (rail transport), wheelsets (two Railroad wheel, wheels on an axle), in a frame, attached under a vehicle by a pivot. Bogies take various forms in various modes ...

truck A truck or lorry is a motor vehicle designed to transport freight, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame construct ...

" in

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

) – a pivoted frame assembly holding at least two wheelsets – at each end of the vehicle. Most modern

freight cars A railroad car, railcar (American English, American and Canadian English), railway wagon, railway carriage, railway truck, railwagon, railcarriage or railtruck (British English and International Union of Railways, UIC), also called a tra ...

and

passenger cars A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...

have bogies each with two wheelsets, but three wheelsets (or more) are used in bogies of freight cars that carry heavy loads, and three-wheelset bogies are under some passenger cars. Four-wheeled

goods wagon Goods wagons or freight wagons (North America: freight cars), also known as goods carriages, goods trucks, freight carriages or freight trucks, are unpowered railway vehicles that are used for the transportation of cargo. A variety of wagon types ...

s that were once near-universal in

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

and

Great Britain Great Britain is an island in the North Atlantic Ocean off the north-west coast of continental Europe, consisting of the countries England, Scotland, and Wales. With an area of , it is the largest of the British Isles, the List of European ...

and their colonies have only two wheelsets; in recent decades such vehicles have become less common as trainloads have become heavier.

Conical wheel-tread

Most

train wheel A train wheel or rail wheel is a type of wheel specially designed for use on railway tracks. The wheel acts as a rolling component, typically press fitted on to an axle and mounted directly on a railway carriage or locomotive, or indirectl ...

s have a conical taper of about 1 in 20 to enable the wheelset to follow

curves A curve is a geometrical object in mathematics. Curve(s) may also refer to: Arts, entertainment, and media Music * Curve (band), an English alternative rock music group * Curve (album), ''Curve'' (album), a 2012 album by Our Lady Peace * Curve ( ...

with less chance of the wheel

flange A flange is a protruded ridge, lip or rim (wheel), rim, either external or internal, that serves to increase shear strength, strength (as the flange of a steel beam (structure), beam such as an I-beam or a T-beam); for easy attachment/transfer o ...

s coming in contact with the rail sides, and to reduce curve resistance. The rails generally slant inwards at 1 in 40, a lesser angle than the wheel

cone In geometry, a cone is a three-dimensional figure that tapers smoothly from a flat base (typically a circle) to a point not contained in the base, called the '' apex'' or '' vertex''. A cone is formed by a set of line segments, half-lines ...

. Without the conical shape, a wheel would tend to continue in a straight path due to the

inertia Inertia is the natural tendency of objects in motion to stay in motion and objects at rest to stay at rest, unless a force causes the velocity to change. It is one of the fundamental principles in classical physics, and described by Isaac Newto ...

of the rail vehicle, causing the wheelset to move towards the outer rail on the curve. The cone increases the effective diameter of the wheel as it moves towards the outer rail, and since the wheels are mounted rigidly on the axle, the outer wheels travel slightly farther, causing the wheelsets to more efficiently follow the curve. Abnormal wear at the wheel–rail interface is thus avoided, along with the loud, piercing, very high-pitched squeal which usually results from it – especially evident on curves in tunnels, stations and elevated track, due to flat surfaces slipping and flanges grinding along the rail. However, if the degree of conicality is inappropriate for the suspension and track, an unpleasant

oscillation Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

can occur at high speeds. Recent research is also showing that marginal changes to wheel and rail profiles can improve performance further. Not all railroads have employed conical-tread wheels. The

Bay Area Rapid Transit Bay Area Rapid Transit (BART) is a rapid transit system serving the San Francisco Bay Area in California. BART serves 50 stations along six routes and of track, including eBART, a spur line running to Antioch, and Oakland Airport Connecto ...

(BART) system in

San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...

, built with cylindrical wheels and flat-topped rails, started to re-profile the wheels in 2016 with conical treads after years of complaints about the squeal by its passengers. Australia's Queensland Railways used cylindrical wheels and vertical rails until the mid-1980s, when considerably higher train loads made the practice untenable.

Specialised wheelsets

Some

rubber-tyred metro A rubber-tyred metro or rubber-tired metro is a form of rapid transit system that uses a mix of road transport, road and rail transport, rail technology. The vehicles have wheels with rubber tires that run on a roll way inside guide bars for tr ...

s feature special wheelsets with

rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Types of polyisoprene ...

tyres outside of deep-flanged steel wheels, which guide the bogie through standard

railroad switch A railroad switch (American English, AE), turnout, or (set of) points (Commonwealth English, CE) is a mechanical installation enabling railway trains to be guided from one Rail tracks, track to another, such as at a Junction (rail), ...

es and keep the train from derailing if a tyre deflates. The

system A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its open system (systems theory), environment, is described by its boundaries, str ...

was originally conceived by

Michelin Michelin ( , ), in full ("General Company of the Michelin Enterprises P.L.S."), is a French multinational tyre manufacturing company based in Clermont-Ferrand in the Auvergne-Rhône-Alpes '' région'' of France. It is the second largest t ...

for the

Paris Métro The Paris Métro (, , or , ), short for Métropolitain (), is a rapid transit system serving the Paris metropolitan area in France. A symbol of the city, it is known for its density within the capital's territorial limits, uniform architectur ...

; the first line opened in 1956.

Gallery

File:Denney Axle.jpg, Denney axle File:Rollingstock axle.jpg, Railroad car wheels are rigidly mounted on an axle to rotate in unison. File:SBB Cargo Güterwagen Radsätze.jpg,

Swiss Federal Railways Swiss Federal Railways (, SBB; , CFF; , FFS) is the national railway company of Switzerland. The company was founded in 1902 and is headquartered in Bern. It used to be a State-owned enterprise, government institution, but since 1999 it has be ...

wheelsets with fitted journals File:Rail axl at Texas Transportation museum.JPG, Wheelset from a railroad speeder. The wheels are pressed steel and the flanges are smaller than those of full-sized rail vehicles. File:GWR Spoked wagon wheels.jpg, A wheelset from a

Great Western Railway The Great Western Railway (GWR) was a History of rail transport in Great Britain, British railway company that linked London with the southwest, west and West Midlands (region), West Midlands of England and most of Wales. It was founded in 1833, ...

wagon, showing a

plain bearing file:NYC 100-driving-axle-friction-bearing.jpg, Plain bearing on a 1906 S-Motor locomotive showing the axle, bearing, oil supply and oiling pad file:Linear-table with detail numbered.png, A sliding table with four cylindrical bearings file:GWR Spo ...

end File:Bettendorf truck at Illinois Railway Museum.JPG, A freight bogie of the Bettendorf pattern, which became standard in North America and elsewhere File:Пам.Энгельса29 КП Метро Штангист в каске.JPG, Wheelset as part of a welded sculpture in

Kharkiv Kharkiv, also known as Kharkov, is the second-largest List of cities in Ukraine, city in Ukraine.

File:Heidelberg funicular wheelset.jpg, Wheelset of a two-rail funicular with the Abt switch turnout File:Muzeum MHD, dvoukolí vozu petřínské lanovky 1891.jpg, Funicular wheelset with Abt rack and pinion brake File:Budapešť,_Városmajor,_pomník_zubačky.jpg, Wheelset of a

rack railway A rack railway (also rack-and-pinion railway, cog railway, or cogwheel railway) is a steep grade railway with a toothed rack rail, usually between the running rails. The trains are fitted with one or more cog wheels or pinions that mesh with ...

References

External links

* {{Authority control Bogie

Conical wheel-tread

Specialised wheelsets

Gallery

See also

References

Further reading

External links