![Rail vehicle wheelset](https://upload.wikimedia.org/wikipedia/commons/2/2a/Rail_vehicle_wheelset.png)
A wheelset is a pair of
railroad vehicle wheels
A wheel is a circular component that is intended to rotate 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 axles, allow heavy objects to b ...
mounted rigidly on an
axle such that both wheels rotate in unison. Wheelsets are often mounted in a
bogie ("truck" in
North America) – a pivoted frame assembly holding at least two wheelsets – at each end of the vehicle. Most modern
freight cars
A railroad car, railcar (American and Canadian English), railway wagon, railway carriage, railway truck, railwagon, railcarriage or railtruck (British English and UIC), also called a train car, train wagon, train carriage or train truck, is a ...
and
passenger cars
A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods.
The year 1886 is regarded as ...
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 wagons
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 type ...
that were once near-universal in
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...
and
Great Britain
Great Britain is an island in the North Atlantic Ocean off the northwest coast of continental Europe. With an area of , it is the largest of the British Isles, the largest European island and the ninth-largest island in the world. It i ...
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 onto an axle and mounted directly on a railway carriage or locomotive, or indirectly on a b ...
s have a
conical taper of about 1 in 20 to enable the wheelset to follow
curves with less chance of the wheel
flange
A flange is a protruded ridge, lip or rim, either external or internal, that serves to increase strength (as the flange of an iron beam such as an I-beam or a T-beam); for easy attachment/transfer of contact force with another object (as the f ...
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
A cone is a three-dimensional geometric shape that tapers smoothly from a flat base (frequently, though not necessarily, circular) to a point called the apex or vertex.
A cone is formed by a set of line segments, half-lines, or lines con ...
. Without the conical shape, a wheel would tend to continue in a straight path due to the
inertia
Inertia is the idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law ...
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 The wheel–rail interface is the area of contact between wheels and rails of railways
Rail transport (also known as train transport) is a means of transport that transfers passengers and goods on wheeled vehicles running on rails, which are i ...
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 (BART) system in
San Francisco
San Francisco (; Spanish for " Saint Francis"), officially the City and County of San Francisco, is the commercial, financial, and cultural center of Northern California. The city proper is the fourth most populous in California and 17th ...
, 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
Queensland Rail (QR) is a railway operator in Queensland, Australia. Owned by the Queensland Government, it operates local and long-distance passenger services, as well as owning and maintaining approximately 6,600 kilometres of track and relate ...
used cylindrical wheels and vertical rails until the mid-1980s, when considerably higher train loads made the practice untenable.
Specialised wheelsets
![Bogie-metro-Meteor-p1010692](https://upload.wikimedia.org/wikipedia/commons/f/fd/Bogie-metro-Meteor-p1010692.jpg)
Some
rubber-tyred metros 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. Thailand, Malaysia, an ...
tyres outside of deep-flanged steel wheels, which guide the bogie through standard
railroad switch
A railroad switch (), turnout, or ''set ofpoints () is a mechanical installation enabling railway trains to be guided from one track to another, such as at a railway junction or where a spur or siding branches off.
The most common t ...
es and keep the train from
derailing
In rail transport, a derailment occurs when a rail vehicle such as a train comes off its rails. Although many derailments are minor, all result in temporary disruption of the proper operation of the railway system and they are a potentially ...
if a tyre deflates. The
system was originally conceived by
Michelin for the
Paris Métro
The Paris Métro (french: Métro de Paris ; short for Métropolitain ) is a rapid transit system in the Paris metropolitan area, France. A symbol of the city, it is known for its density within the capital's territorial limits, uniform architec ...
; the
first line opened in 1956.
Gallery
File:Denney Axle.jpg, Denney axle Denney may refer to:
* Denney, Territoire de Belfort, a commune in Belfort department, France
* Denney (surname), people with the surname ''Denney''
{{disambig ...
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 wheelsets with fitted journals
File:Rail_axl_at_Texas_Transportation_museum.JPG, Wheelset from a railroad speeder
A speeder (also known as a section car, railway motor car, putt-putt, track-maintenance car, crew car, jigger, trike, quad, trolley, inspection car, or a draisine) is a small railcar formerly used around the world by track inspectors and work cre ...
; 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 wagon, showing a plain bearing
A plain bearing, or more commonly sliding contact bearing and slide bearing (in railroading sometimes called a solid bearing, journal bearing, or friction bearing), is the simplest type of bearing, comprising just a bearing surface and no roll ...
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 ( uk, wikt:Харків, Ха́рків, ), also known as Kharkov (russian: Харькoв, ), is the second-largest List of cities in Ukraine, city and List of hromadas of Ukraine, municipality in Ukraine.[funicular
A funicular (, , ) is a type of cable railway system that connects points along a railway track laid on a steep slope. The system is characterized by two counterbalanced carriages (also called cars or trains) permanently attached to opposite e ...]
File:Muzeum MHD, dvoukolí vozu petřínské lanovky 1891.jpg, Funicular wheelset with Abt rack and pinion brake
See also
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Axle box
A bogie or railroad truck holds the wheel sets of a rail vehicle.
Axlebox
An ''axle box'', also known as a ''journal box'' in North America, is the mechanical subassembly on each end of the axles under a railway wagon, coach or locomotive; ...
*
Beam axle
A beam axle, rigid axle or solid axle is a dependent suspension design in which a set of wheels is connected laterally by a single beam or shaft. Beam axles were once commonly used at the rear wheels of a vehicle, but historically they have als ...
*
Axle exchange
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Drop table
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Flat spot
A flat spot, or wheel flat, also called spalling or shelling, is a fault in railroad wheel shape. A flat spot occurs when a rail vehicle's wheelset is dragged along the rail after the wheel/axle has stopped rotating. Flat spots are usually cau ...
*
Gölsdorf axle
The Gölsdorf axle system is used on railway Gölsdorf locomotives to achieve quiet running and low wear-and-tear when negotiating curves. The axle system comprises a combination of fixed axles and axles that can slide transversely, all within a si ...
*
Interference fit
An interference fit, also known as a pressed fit or friction fit is a form of fastening between two ''tight'' fitting mating parts that produces a joint which is held together by friction after the parts are pushed together.
Depending on the am ...
*
International Heavy Haul Association The International Heavy Haul Association is an association of Heavy Haul railways that researches problems with the rail- wheel interface.
Overview
The extreme axleloads found on mineral railways such as iron ore railways in the Pilbara
Th ...
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Journal box
A bogie or railroad truck holds the wheel sets of a rail vehicle.
Axlebox
An ''axle box'', also known as a ''journal box'' in North America, is the mechanical subassembly on each end of the axles under a railway wagon, coach or locomotive; ...
*
List of railroad truck parts
A bogie or railroad truck holds the wheel sets of a rail vehicle.
Axlebox
An ''axle box'', also known as a ''journal box'' in North America, is the mechanical subassembly on each end of the axles under a railway wagon, coach or locomotive; ...
*
Luttermöller axle A Luttermöller axle is an unusual steam locomotive component. Steam locomotives with several axles or wheelsets connected to one another by coupling rods are not able to negotiate tight curves well. In order to assist such locomotives, the manager ...
*
Plain bearing
A plain bearing, or more commonly sliding contact bearing and slide bearing (in railroading sometimes called a solid bearing, journal bearing, or friction bearing), is the simplest type of bearing, comprising just a bearing surface and no roll ...
*
Rolling-element bearing
*
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 onto an axle and mounted directly on a railway carriage or locomotive, or indirectly on a b ...
*
Variable gauge axles
A variable gauge system allows railway vehicles in a train to travel across a break of gauge between two railway networks with different track gauges.
For through operation, a train must be equipped with special bogies holding variable gauge whe ...
*
Wheelbase
In both road and rail vehicles, the wheelbase is the horizontal distance between the centers of the front and rear wheels. For road vehicles with more than two axles (e.g. some trucks), the wheelbase is the distance between the steering (front ...
*
Wheel gauge
References
Further reading
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External links
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Train wheels
{{Authority control
Bogie