axleboxes

An axlebox is a housing on a railway vehicle that contains the bearing supporting a wheel axle. It is mounted on the bogie or axlebox yoke and is closed by end caps or covers. The term is commonly used in British and European practice; in some contexts the same component is called an axle bearing housing or axle bearing unit. The axlebox encloses the bearing and provides access for lubrication, inspection, and mounting hardware.

There are two main types of axleboxes. Plain bearing axleboxes use a bushing or liner made of white metal or bronze, relying on grease or oil lubrication to reduce friction. Roller bearing axleboxes house rolling element bearings (such as spherical, cylindrical, or tapered rollers) within a rigid housing and typically employ sealed lubrication or a cartridge system, offering reduced maintenance and longer service life. Modern designs often favor sealed roller-bearing axleboxes for freight and high-speed applications.

The axlebox serves several functions. It supports radial and end loads transmitted by the wheelset to the bogie frame, helps align the axle, and contains the lubrication system to minimize wear. It also provides a seal to limit contamination and, in some designs, channels excess lubricant away from critical surfaces.

Maintenance and inspection are essential. Technicians check for cracks, corrosion, leaks, and wear, verify lubrication levels and condition, inspect seals and gaskets, and measure clearances. Components may be replaced as a unit or as individual parts depending on the design and maintenance regime. Proper maintenance of axleboxes is critical to axle alignment, bearing life, and overall railway safety.