Introduction to Axle Bearings for Railway Rolling Stock

Introduction to Axle Bearings for Railway Rolling Stock
Characteristics of Axle Bearings
Rolling stock axle bearings are subject to radial impact
loads caused by rail joints, switches and sometimes wheel
flats, as well as to the static and dynamic radial loads of
vehicle weight. They are also liable to receive axial loads
generated by lateral movement as trains run on curved
rails or in a snaking motion. All of these loads together
form complex combinations that act on axle bearings.
Axle bearings must therefore be designed on the basis of
not only dimensional requirements of the axle journal and
bearing box geometry, but also these complex load
conditions. Additionally, as axle bearings play a critical
role in the safety of railroad operation, they are periodically
disassembled for inspection. For this reason, simple and
dependable procedures for disassembly, inspection and
re-assembly are important design factors as well. Utilizing
its vast know-how and experience, NSK has designed,
manufactured and supplied a wide variety of axle bearings.
Types of Axle Bearings and Their Applications
Axle bearings currently in use are classified into the
following six types based both on bearing type and
sealing device:
1. RCT Bearings (Sealed-Clean Rotating End Cap Tapered
Roller Bearings)
2. RCC Bearings (Sealed-Clean Rotating End Cap Cylindrical
Roller Bearings)
3. Spherical roller bearings
4. Cylindrical roller bearings combined with ball bearings
5. Cylindrical roller bearings with ribs
6. Tapered roller bearings
To ensure sufficient load-carrying capacity, all of these
types are usually manufactured in double-row
configurations.
Globally, while plane bearings are still widely used, rolling
bearings are increasingly being selected to replace them.
All types of radial roller bearings, including tapered roller
bearings, spherical roller bearings and cylindrical roller
bearings, have been used in rolling stock axles based on
the particular merits of each type.
To improve operating efficiency, bearings must offer
longer inspection intervals, simplified maintenance
procedures and increased integration of bearing
components and adjacent parts. To meet these needs,
unitized bearings with advanced sealing devices have
been introduced and are now widely used in modern
rolling stock.
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