Fundamentals of Rail Vehicle Dynamics: Guidance and Stability

Alan Wickens was Director of Research at British Rail, and already highly respected internationally in the field of railway vehicle dynamics, when this reviewer joined BR Research as a new graduate in 1980. At that time, much of the basic knowledge in railway engineering was being developed by the state railways and was generally passed on from one generation to the next. The world has changed since then and an understanding of the railway system is now required by many engineers within the wider railway industry and its diverse suppliers. Vehicle dynamics is now studied across many organizations, in particular through the use of several commercially available software packages. It is a relatively mature science, but the reliance on a software package can lead to the neglect of the basic insight that was the hallmark of earlier generations of engineers. As the preface to the book puts it, ‘computer output must be tempered with understanding and scepticism’. It is therefore timely that this book on the fundamentals of rail vehicle dynamics should be published. Professor Wickens, now Emeritus Professor at Loughborough University, was largely responsible for defining modern rail vehicle dynamics, beginning in the 1960s, and is thus well qualified to write the definitive text on this subject. As stated in its title, this book is about fundamentals. It therefore sets out to describe principles, not the specifics, of any particular vehicle design. However, as its opening sentence states, ‘the railway vehicle is one of the most complex dynamical systems in engineering’. Thus, although it is about fundamentals, it is not suitable on its own as an introductory text for the complete beginner. It requires, in fact, quite a wide prior subject knowledge of both dynamic analysis and the railway system. For example, concepts such as cant, cant deficiency, conicity or Hertzian stiffness are given little explanation. Chapter 1 forms a brief introduction to the basic concepts of the railway vehicle dynamic system. Chapter 2 sets out the equations of motion of the wheelset and ultimately the two-axle vehicle, including coverage of creep forces and creepage. Subsequent chapters deal with the issues of guidance, principally curving behaviour, and stability, which is the onset of unstable ‘hunting’ behaviour at a certain speed. Chapter 3 covers the single wheelset, Chapters 4 and 5 the two-axle vehicle or bogie and Chapter 6 the bogie vehicle; the last three chapters deal with three-axle vehicles, articulated vehicles and unsymmetrical vehicles. The compromises in vehicle design between the requirements for curving and stability lie at the heart of most vehicle dynamics calculations. As is clear from the title, no attention is given to vertical dynamics or ride, which would require another book on their own. A strong point is that the book is well grounded in literature. Around 250 references are given, although as they are given at the end of each chapter this number includes some overlap; a single reference list would have been preferable in many ways. The historical basis of the subject is also well covered, as well as aspects that bring the topic up to date quite well. Inevitably, the references include some BR Research reports, which are not generally available. Nevertheless, the comprehensive survey of literature included in the book is a very useful aspect. The text is well written, if difficult in places. Throughout, graphs are given of numerical examples that are mainly helpful in illustrating the text, although the interpretation of some of the less obvious figures could be explained more clearly in places. Mostly the data used in producing the examples are given, the main exception being the ‘typical’ wheel and rail transverse profiles used throughout, which are only given graphically. The inclusion of these data, and possibly example programs either in appendices or on an enclosed disc, would have enhanced the usefulness of the book, allowing readers to explore various aspects for themselves. From a production point of view, the quality of the figures is rather varied, with many graphs suffering from quantization effects, making the lines ‘wiggly’ when presumably this is not intended. Where multiple lines are present in a single graph, which is often, they are mostly of the same line style, which makes identification difficult at times. The system of section and equation numbering can be rather confusing, although it is explained clearly at the beginning, and it is not clear when looking at an average page in which section or chapter it is located. Despite these minor criticisms, as a thorough and definitive text on a difficult subject this book should be widely welcomed. D J Thompson Institute of Sound and Vibration University of Southampton 265