How its Made Machines
All wheel profiles are regularly checked to ensure proper interaction between the wheel and the rail. Incorrectly profiled wheels and worn wheels can increase rolling resistance, reduce energy efficiency and may even cause a derailment.
A train wheel (rail wheel) is a type of wheel specially designed for use on railway tracks. The wheel acts as a rolling component, typically pushed onto an axle and mounted directly on a railway carriage or locomotive, or indirectly on a bogie (in the UK), also called a truck (in North America). The powered wheels under the locomotive are called Driving Wheels. Wheels are initially cast or forged and then heat-treated to have a specific hardness. New wheels are machined using a lathe to a standardized shape, called a profile, before being installed onto an axle.
Train wheels have a flange on one side to keep the wheels, and hence the train, running on the rails when the limits of the geometry-based alignment are reached, e.g. due to some emergency or defect. See Hunting oscillation. Most train wheels have a conical geometry, serving as the primary means of keeping the train's motion aligned with the track while others have a cylindrical geometry such that the flanges are essential to keep the train on the rail track.
The number of wheels per locomotive or car vary in both size and number to accommodate the needs of the railcar or locomotive. Regardless of these factors, pairs of identically sized wheels are always affixed to a straight axle as a singular unit, called a wheelset.
Wheels used for road-rail vehicles are normally smaller than those found on other types of rolling stock (such as locomotives or carriages). This is because the wheel has to be stored clear of the ground when the vehicle is in road-going mode - Such wheels can be as small as 245 mm (9.65 in) in diameter. In Australia, wheels for road-rail vehicles should comply with the requirements of AS7514.4, which is the standard for infrastructure maintenance vehicle wheels. More details
