Radial axle

A radial axle is an axle on a railway locomotive or carriage which has been designed to move laterally, along the arc of a circle, when entering a curve in order to reduce the flange and rail wear.

Radial axles were widely used on carriages in the late 19th century before the adoption of bogies. They were also used on the leading or trailing carrying axles of locomotives, particularly tank locomotives. The idea was first tried successfully by William Bridges Adams on the London and South Western Railway in 1863 and was known as the Adams Axle. It was subsequently taken up by other engineers, notably his namesake William Adams, Locomotive Superintendent of the LSWR, who introduced a class now known as "Adams Radials".