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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 bogie (in the UK), also called a truck (in North America).
Most train wheels have a conical taper of about 1 in 20 to enable the wheelset to follow curves with less chance of the wheel flanges 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.
Especially in steam days, wheel arrangement was an important attribute of a locomotive because there were many different types of layout adopted, each wheel being optimised for a different use (often with only some being actually "driven"). Modern diesel and electric locomotives are much more uniform, usually with all axles driven.
Side friction wheels keep the train centered in the track, avoiding derailment. The final set of wheels in the assembly are known as running wheels, road wheels, or tractor wheels. Running wheels are typically the largest set of wheels in the assembly, and roll on the top of the rails. These wheels bear the weight of the train.
Steel tire on a steam locomotive's driving wheel is heated with gas flames to expand and loosen it so it may be slipped over the wheel.. The steel wheel of a steam locomotive and other older types of rolling stock were usually fitted with a steel tire (American English) or tyre (in British English, Australian English and others) to provide a replaceable wearing element on a costly wheel.
The frictional force on the rails and the amount of wheel slip drops steadily as the train picks up speed. A driven wheel does not roll freely but turns faster than the corresponding locomotive velocity. The difference between the two is known as the "slip velocity". "Slip" is the "slip velocity" compared to the "vehicle velocity".
A Talgo train with a locomotive can drive across a gauge change at 1 axle per second at a speed of about 10–15 km/h (6.2–9.3 mph). [35] [36] A train (or an individual car) can be pushed halfway across the gauge-changer, uncoupled, and then (once far enough across) coupled to the new locomotive and pulled the rest of the way.
The horizontal (cone-shaped) rim makes contact with the slightly convex top of a steel rail in different (horizontal) places so that the outer wheel has a larger effective diameter than the inner wheel. With both tram and train wheels, this happens naturally because the tires are cone shaped sloping surfaces: the inside diameter is a few ...