A wheelset is the wheel

Wheel

A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...

-axle

Axle

An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...

 assembly of a railroad car

Railroad car

A railroad car or railway vehicle , also known as a bogie in Indian English, is a vehicle on a rail transport system that is used for the carrying of cargo or passengers. Cars can be coupled together into a train and hauled by one or more locomotives...

. The frame assembly beneath each end of a car, railcar

Railcar

A railcar, in British English and Australian English, is a self-propelled railway vehicle designed to transport passengers. The term "railcar" is usually used in reference to a train consisting of a single coach , with a driver's cab at one or both ends. Some railways, e.g., the Great Western...

 or 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...

 that holds the wheelsets is called 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...

 (or truck in 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...

). Most North American freight cars have two bogies with two or three wheelsets, depending on the type of car; short freight cars

Goods wagon

Goods wagons are railway wagons that are used for the transportation of goods .- Development :At the beginning of the railway era, the vast majority of goods wagons were four-wheeled vehicles of simple construction. These were almost exclusively small covered wagons, open wagons with side-boards,...

 generally have no bogies but instead have two wheelsets.

Grovers bogie

Two axle cars operating on lines with sharp curves, such as Queensland Railways, used Grovers bogies.

Conical shape

Most wheels have a conical shape of about 1 in 20. The conical shape has the effect of steering the wheelset around curves, so that the flange

Flange

A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...

s rarely come into play. The rails generally slant in at the same rate as the wheel conicity. As the wheels approach a curve, they will tend to follow a straighter path. This causes the wheelset to shift sideways on the track so that the effective diameter of the outer wheels is greater than that of the inner ones. Since the wheels are joined rigidly by the axle, the outer wheels will travel further, causing the train to naturally follow the curve.

For more information see Hunting oscillation

Hunting oscillation

Hunting oscillation is an oscillation, usually unwanted, about an equilibrium. The expression came into use in the 19th century and describes how a systems 'hunts' for equilibrium...

.

For its first hundred years, Queensland Railways used cylindrical wheels and vertical rails.

See also

• Axle track
• Drop table
• Plain bearing
  Plain bearing
  A plain bearing, also known as a plane bearing or a friction bearing is the simplest type of bearing, comprising just a bearing surface and no rolling elements. Therefore the journal slides over the bearing surface. The simplest example of a plain bearing is a shaft rotating in a hole...
  
  
• Variable gauge axles
  Variable gauge axles
  A variable gauge system allows railway vehicles in a train to travel across a break of gauge caused by two railway networks with differing track gauges....
  
  
• Wheelbase
  Wheelbase
  In both road and rail vehicles, the wheelbase is the distance between the centers of the front and rear wheels.- Road :In automobiles, the wheelbase is the horizontal distance between the center of the front wheel and the center of the rear wheel...