Wheelset (railroad).html



Two wheelsets in a North American (Bettendorf-style) freight bogie displayed at the Illinois Railway Museum.

(Flanges not shown for clarity)

Train wheels are usually affixed to a straight axle, such that both wheels rotate in unison. Talgo wheelsets are an exception.

A wheelset is the wheel-axle (wheel and axle) assembly of a railroad car. The frame assembly beneath each end of a car or locomotive that holds the wheelsets is called the bogie (or truck in North America). Most North American freight cars have two bogies with two or three wheelsets, depending on the type of car, while European freight cars generally have no bogies but instead have two wheelsets.

Conical shape

Most wheels have a conical shape of about 1 in 20, which amongst other things helps extract the wheel from its mold after casting. The conical shape also has the effect of steering the wheelset around curves, so that the flanges come into play only some of the time. The rails generally slant in at the same rate as the wheel conicity.

Queensland Railways had cylindrical wheels for the first 100 years.

Each wheelset for a standard class rail carriage in the UK costs on average £16,000 which for the longevity of the sets is one of the most efficient in the transport system today at the average cost of £4000 per wheel that lasts over 1,500,000 hours in service.

Wheel and rail profiles

Wheel and rail profiles aren't straight, but follow specific shapes that have been found to follow curves and reduce hunting, and to reduce wear and tear.

Heavy traffic and high axle loads on iron ore railways in the Pilbara cause serious damage to wheels and rails, leading to fundamental research on the Rail-Wheel Interface. This information has been made available to the world through the International Heavy Haul Association (IHHA). ¹

Hub to rim connection

The metal connecting the hub of the wheel to the rim is thin to save weight. Originally it was straight. However, wheels get hot when brakes are applied, and the straight connection caused stresses that could cause fractures. It was then realized that the connection between hub and rim could be made with a curve which could absorb such heat stresses better and safer.

See also

• Variable gauge axles
• Wheel and axle

References

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