Wheelset (rail transport)

A wheelset is the wheel-axle assembly of a railroad car. The frame assembly beneath each end of a car, railcar 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; short freight cars 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 flanges 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.

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

See also

• Axle track
• Drop table
• Plain bearing
• Variable gauge axles
• Wheelbase

References

• Matthias N. Forney (1879; reprint 1974). The Railroad Car Builder's Dictionary. Dover Publications, Inc.. 
• John H. White, Jr. (1978). The American Railroad Passenger Car. Johns Hopkins University Press. 
• John H. White, Jr. (1993). The American Railroad Freight Car. Johns Hopkins University Press.