SKF railway bogie design

Today, very different railway bogie design principles are applied. The main focus of this chapter are the bogie features that are directly or indirectly related to the axlebox application. The main ones are bogie design principle parameters, guiding / suspension, primary spring and damping principles that are interacting with the design of axleboxes and bearings. Design principles A bogie is a structure underneath a railway vehicle body to which axles and wheels are attached through bearings. The term “railway bogie” is used in British English, while a “wheel truck”, or simply “truck” is used in American English. The overall term is “running gear”, which covers bogies as well as vehicles with two, or more axles without any bogies. In this case, these axles are directly fitted to the vehicle body via guiding devices and springs, and for very low speeds even without springs. Running gears serve a number of purposes: • support of the rail vehicle body • stability on both straight and curved tracks • providing ride comfort by absorbing vibration, and minimizing centrifugal forces when the train runs on curves at high-speed • minimizing generation of track irregularities and rail abrasion 25 2 Design principle elements railway bogies are complex subsystems in railway vehicles and contain brake systems, drive systems including gearbox coupling and traction motors for powered wheelsets, bogie frames with secondary spring systems and the wheelset subsystems, which are basically the assembly of two wheels and an axle. In this chapter, the focus is on some general bogie design principles and especially design features that interact with the axlebox bearing system. Directly connected to the wheelset and the bogie frame is the axlebox († chapter 3) containing the axlebox bearing system († chapter 4 and chapter 5). The axlebox is very much linked to further subsystems and components like primary spring systems, axlebox guidance, dampers, steering mechanisms of wheelsets, earth return devices as well as sensors to detect operational parameters († chapter 7) and bogie monitoring systems († chapter 8). Further bogie-connected subsystems are wheel flange lubrication systems, articulation joints, slewing bearings and special plain bearings for damper supports († chapter 9). Running gears and bogies All kinds of railway vehicles are equipped with running gears, which can be designed as 2- or 3-axle cars or as bogie vehicles. 2-axle car design principles are used mainly for European freight cars, shunting locomotives and for sections of articulated cars such as low-floor light rail vehicles or tramways. Bogie designs Today, the majority of railway vehicles are equipped with bogies that contain mostly two axles, but in some cases, such as heavier and powerful locomotives, 3-axle designs are used. Because of the shorter axle distance of bogie designs, longer vehicles/vehicle sections can be used. On the other hand, the riding comfort of bogie vehicles is much better than vehicles equipped with axles that are supported directly by the vehicle body. Design principles of running gears and bogies On top: 2-axle vehicle Middle and bottom: articulated vehicles based on 2-axle running gear designs applied for light rail vehicles Design principle of a bogie vehicle Jacobs bogie design principle Jacobs bogie designs A common bogie design principle, used especially for connected railway vehicle bodies for multiple units, special freight cars and mass transit vehicles, are Jacobs bogies1). These bogies support two body ends via one bogie. This design contributes to mass saving and running stabilization, resulting in a better riding performance for some applications. Example of a typical low-floor multisection tramway design 1) Jacobs bogies named after Wilhelm Jakobs (1858–1942) Rail Axles Pivot Bogies 26 Powered bogie designs Locomotives, multiple units such as highspeed trains as well as mass transit vehicles, are equipped with powered bogies. Typical propulsion systems contain a wheelset, a gearbox and a traction motor. More sophisticated designs are equipped with hollow shafts and couplings to reduce unsprung mass. Longitudinal propulsion (drive) systems contain a helical gearbox and cardan shafts. Hydraulic diesel propulsion systems contain mostly gearboxes and cardan shafts, connecting two bogie drives to one main gearbox and the hydraulic gearbox system connected to the diesel motor. Powered railway  bogie, transverse drive Powered bogie, longitudinal drive Radial steering principles To reduce the forces between rails and wheels, several radial steering design principles for wheelsets are applied. The aim of these designs is to reduce wear and noise caused by low steering forces. Designs with connected wheelsets and wheelsets connected to the vehicle body are based on lever systems that act on the wheelsets via the axleboxes.