- Email: [email protected]
Ball and roller bearings
Ball and roller bearings Theory, Design and Application, Second edition. L Hasbargenand J Brandlein The information contained within old books can lose credibility in the eyes of readers new to a subject, especially in scientific and technical matters. During my review of this second edition of Ball and Roller Bearings I sought to borrow the first edition for reference from our Library and was required to wait for a day while it was retrieved from the archives. In fact much of that which the first edition contains is still applicable today, but revision was necessary for three main reasons. Firstly, as the Editors point out in their Foreword, there is 30 years' accumulation of knowledge since the book was first published in the fields of fatigue, friction, wear and lubrication, together with significant advances in the quality of rolling bearing steels. Secondly, the book has benefited from an up-to-date layout and style, both in the text and in the many illustrations. Thirdly, the book now uses SI units throughout. The first seven chapters are divided into a total of one hundred and thirty-two topic headings covering every aspect of roiling bearing design theory material specification and usage as is currently applicable to the standard commercially available ranges. It does not enter into the realms of future developments although such topics will undoubtedly be found in the many references. The authors draw much of the information and data on bearing design and usage from FAG Kugelfischer Gorg Schafer KGaA. Such is the degree of standardisation in the bearing industry, however, that the relevance of the book to rolling bearings in general is in no way impaired. John Wiley, Chichester 1986 £32.50
224
Because it is a 'state of the art' book the first chapter details all the types of commercially available rolling bearing and then goes on to describe the materials from which they are made. Finally, tolerances and methods of checking are covered but not manufacturing processes. In Chapter Two all the principles upon which bearing designs are based are outlined, ranging over geometry, kinematics, Hertzian stress and load distribution. The coverage is concise and summarises the main formulae, giving references which are listed at the end of the book. In a section headed 'Rolling motion and rolling contact friction' the kinematics of a thrust loaded ball bearing are explained, showing how spin may be present in a rolling contact. The relevance of contact friction in determining how the balls rotate and whether or not contact spin causes significant frictional loss is left vague. This analysis did not appear at all in the first edition. In the intervening thirty years the concept of raceway control was proposed by A B Jones in 1959 and has now almost been superceded with increasing knowledge of lubrication in elliptical contacts. The still incomplete research evidence in this area is referred to again in the chapter on lubrication. Chapter Three contains an extensive coverage of the various considerations upon which load capacity and life expectancy are based. Much of what is presented is the result of many years of experience relating to fatigue failure of the rolling elements and raceways, although the actual contact stresses which exist in any particular loading condition are shown to be calculable from the Hertzian theory. Wear receives a much greater coverage in
this second edition than it did in the first because of the accumulation of data over the years. The relationship between wear and service life is much more empirical than fatigue and service life because of the fact that, in theory, properly lubricated rolling contacts do not wear at all. It is the introduction of foreign debris, particularly from outside the bearing (as opposed to fatigue debris from within), which causes wear of the rolling surfaces and this is largely related to operating environment. The new edition therefore presents a comprehensive table listing some eighty types of bearing application and sets against each an expected wear factor and a permissible wear factor, based on investigations conducted with 100 000 bearings. Chapter Four considers the lubrication requirements of rolling contact bearings together with its relationship to bearing friction and operating temperature. Again, there is much experience based data given, particularly on expected temperature ranges for different types of installation. Some typical friction coefficients are also given although such values are always of a low order, typically 0.002. The fundarhental reasons are given as to why internal friction arises in what are at first sight purely rolling situations. Lubricant properties and the two principal lubrication regimes, namely hydrodynamic and elastohydrodynamic are treated in sufficient depth for the more investigative user to be able to analyse a particular condition in an attempt to prevent premature bearing failure. Standard methods of lubrication ranging from grease through various oil supply systems to oil mist methods are well illustrated. Chapters Five and Six between them cover aspects concerning design requirements to ensure satisfactory operation of the installed rolling bearing. Topics covered include arrangements of bearing types to meet operating criteria, limiting speeds shaft and
August 1987 Vol 20 No 4
housing fits, noise control and sealing. Finally, mounting and dismounting methods are reviewed, together with measuring instruments that enable the user to check that the bearing and its mating components are compatible.
Selecting bearings for economical and reliable designs
When bearing failure does not occur many users like to identify the type of failure and the cause, especially if the occurrence is thought to be premature. Chapter Seven illustrates, with the aid of some very good photographs, six different types of damage which are directly attributable to bad installation or mis-use in service.
This book is the collection of papers given at the 7th Cheltenham Bearing Conference held in October 1987. The papers cover six presentations on specific bearing topics given at the one-day meeting.
The eighth chapter contains twentyseven application examples of welltried and proven installations. Many of the designs shown are up-dated versions of those shown in the first edition but there are some more recent applications. For instance, the automotive front wheel arrangement now shows front drive, whereas it did not before. There are seven completely new examples in this chapter. No mention is made of rolling bearing usage in gas turbines. In such applications the most severe operating condiditions exist, in particular high speeds and temperatures and where, in the case of aircraft engines, failure can be catastrophic. This is very much a rolling bearing users' book. Anyone interested in using bearings to their maximum advantage and in obtaining an understanding of the principles of bearing design will do well to read it. It also provides good background reading for those engaged upon fundamental research in, for example, bearing dynamics or lubrication and helps to put such work in context. In any situation where premature bearing failure is a recurrent problem, it is quite likely that a clue to the solution will be found in this book. J J Chapman School of Mechanical, Materials and Civil Engineering, Royal Military College of Science (CIT), Shrivenham, Swindon, UK
TR I BOLOGY international
7th Cheltenham Bearing Conference
The title of the book suggests broad guidance for designers on selecting from among the wide range of bearing types available with emphasis on costeffectiveness and reliability. The contents do not fulfil this promise, the coverage of a one-day meeting being necessarily limited. There is, for example, no information on hydrodynamic, hydrostatic, or air bearings nor a review comparing the properties of various bearing types. Nor is there specific information on performance and cost comparisons or reliability. The papers are reviews of particular topics slanted at practising engineers with an interest in bearing technology. A more appropriate title for the book might be 'Some aspects of modern bearing technology'. A paper by Mr A G Herraty of SKF (UK) describes selection methods for roiling element bearings in the context of modern bearing designs. Mr W H Wilson, who has spent many years as an industrial consultant at Leeds Industrial Unit of Tribology, presents a review of materials for plain sliding bearings. This covers basic aspects of metallic and polymeric materials and briefly mentions the use of ceramics and carbon. The idea of magnetic bearings have been around for a long time and there have been some successful applications in specialised areas. The paper by 83 p. Mechanical Engineering Publications 1987. £14.00 (UK) £17.50 (Overseas)
M H Zlotykamien introduces the active bearing technology which has been extensively developed by Societe de Mechanique Magnetique of France. A useful paper by Mr F A Rendall of Ampep presents information on his companies woven glass/PTFE bearing material. This is widely used in spherical bearings, notably for aircraft control mechanisms. Extremely low wear rates can be achieved in suitable dry-sliding applications. The paper presents enough information for a designer to evaluate the use of the material in a potential application and describes a variety of present uses. A joint paper by Dr J M Hampshire and Mr R A Wood, both of RHP bearings, considers the development of standards for roiling bearing load/life ratings leading to ISO 281/1 due to be published this year. There is an interesting review of life adjustment factors with emphasis on the improvements which have been gained from developments in steel quality. The importance of inclusion content, especially alumina, on fatigue life is described along with the RHP approach to steel cleanliness assessment. The last paper by Mr G A W Setford of SPM describes the use of his company's shock pulse metering method for checking lubrication conditions in rolling bearings. The SPM method has been used for many years to monitor bearing condition, especially the onset of surface fatigue. The papers present information available elsewhere in one form or another and do not attempt a comprehensive approach to bearing selection. The practising engineer will find some useful information if he needs an introduction to the topics covered. He will not find full guidance on selecting bearings for economical and reliable designs. L G Hampson National Centre of Tribology, Risley, Warrington, UK,
225
224
Because it is a 'state of the art' book the first chapter details all the types of commercially available rolling bearing and then goes on to describe the materials from which they are made. Finally, tolerances and methods of checking are covered but not manufacturing processes. In Chapter Two all the principles upon which bearing designs are based are outlined, ranging over geometry, kinematics, Hertzian stress and load distribution. The coverage is concise and summarises the main formulae, giving references which are listed at the end of the book. In a section headed 'Rolling motion and rolling contact friction' the kinematics of a thrust loaded ball bearing are explained, showing how spin may be present in a rolling contact. The relevance of contact friction in determining how the balls rotate and whether or not contact spin causes significant frictional loss is left vague. This analysis did not appear at all in the first edition. In the intervening thirty years the concept of raceway control was proposed by A B Jones in 1959 and has now almost been superceded with increasing knowledge of lubrication in elliptical contacts. The still incomplete research evidence in this area is referred to again in the chapter on lubrication. Chapter Three contains an extensive coverage of the various considerations upon which load capacity and life expectancy are based. Much of what is presented is the result of many years of experience relating to fatigue failure of the rolling elements and raceways, although the actual contact stresses which exist in any particular loading condition are shown to be calculable from the Hertzian theory. Wear receives a much greater coverage in
this second edition than it did in the first because of the accumulation of data over the years. The relationship between wear and service life is much more empirical than fatigue and service life because of the fact that, in theory, properly lubricated rolling contacts do not wear at all. It is the introduction of foreign debris, particularly from outside the bearing (as opposed to fatigue debris from within), which causes wear of the rolling surfaces and this is largely related to operating environment. The new edition therefore presents a comprehensive table listing some eighty types of bearing application and sets against each an expected wear factor and a permissible wear factor, based on investigations conducted with 100 000 bearings. Chapter Four considers the lubrication requirements of rolling contact bearings together with its relationship to bearing friction and operating temperature. Again, there is much experience based data given, particularly on expected temperature ranges for different types of installation. Some typical friction coefficients are also given although such values are always of a low order, typically 0.002. The fundarhental reasons are given as to why internal friction arises in what are at first sight purely rolling situations. Lubricant properties and the two principal lubrication regimes, namely hydrodynamic and elastohydrodynamic are treated in sufficient depth for the more investigative user to be able to analyse a particular condition in an attempt to prevent premature bearing failure. Standard methods of lubrication ranging from grease through various oil supply systems to oil mist methods are well illustrated. Chapters Five and Six between them cover aspects concerning design requirements to ensure satisfactory operation of the installed rolling bearing. Topics covered include arrangements of bearing types to meet operating criteria, limiting speeds shaft and
August 1987 Vol 20 No 4
housing fits, noise control and sealing. Finally, mounting and dismounting methods are reviewed, together with measuring instruments that enable the user to check that the bearing and its mating components are compatible.
Selecting bearings for economical and reliable designs
When bearing failure does not occur many users like to identify the type of failure and the cause, especially if the occurrence is thought to be premature. Chapter Seven illustrates, with the aid of some very good photographs, six different types of damage which are directly attributable to bad installation or mis-use in service.
This book is the collection of papers given at the 7th Cheltenham Bearing Conference held in October 1987. The papers cover six presentations on specific bearing topics given at the one-day meeting.
The eighth chapter contains twentyseven application examples of welltried and proven installations. Many of the designs shown are up-dated versions of those shown in the first edition but there are some more recent applications. For instance, the automotive front wheel arrangement now shows front drive, whereas it did not before. There are seven completely new examples in this chapter. No mention is made of rolling bearing usage in gas turbines. In such applications the most severe operating condiditions exist, in particular high speeds and temperatures and where, in the case of aircraft engines, failure can be catastrophic. This is very much a rolling bearing users' book. Anyone interested in using bearings to their maximum advantage and in obtaining an understanding of the principles of bearing design will do well to read it. It also provides good background reading for those engaged upon fundamental research in, for example, bearing dynamics or lubrication and helps to put such work in context. In any situation where premature bearing failure is a recurrent problem, it is quite likely that a clue to the solution will be found in this book. J J Chapman School of Mechanical, Materials and Civil Engineering, Royal Military College of Science (CIT), Shrivenham, Swindon, UK
TR I BOLOGY international
7th Cheltenham Bearing Conference
The title of the book suggests broad guidance for designers on selecting from among the wide range of bearing types available with emphasis on costeffectiveness and reliability. The contents do not fulfil this promise, the coverage of a one-day meeting being necessarily limited. There is, for example, no information on hydrodynamic, hydrostatic, or air bearings nor a review comparing the properties of various bearing types. Nor is there specific information on performance and cost comparisons or reliability. The papers are reviews of particular topics slanted at practising engineers with an interest in bearing technology. A more appropriate title for the book might be 'Some aspects of modern bearing technology'. A paper by Mr A G Herraty of SKF (UK) describes selection methods for roiling element bearings in the context of modern bearing designs. Mr W H Wilson, who has spent many years as an industrial consultant at Leeds Industrial Unit of Tribology, presents a review of materials for plain sliding bearings. This covers basic aspects of metallic and polymeric materials and briefly mentions the use of ceramics and carbon. The idea of magnetic bearings have been around for a long time and there have been some successful applications in specialised areas. The paper by 83 p. Mechanical Engineering Publications 1987. £14.00 (UK) £17.50 (Overseas)
M H Zlotykamien introduces the active bearing technology which has been extensively developed by Societe de Mechanique Magnetique of France. A useful paper by Mr F A Rendall of Ampep presents information on his companies woven glass/PTFE bearing material. This is widely used in spherical bearings, notably for aircraft control mechanisms. Extremely low wear rates can be achieved in suitable dry-sliding applications. The paper presents enough information for a designer to evaluate the use of the material in a potential application and describes a variety of present uses. A joint paper by Dr J M Hampshire and Mr R A Wood, both of RHP bearings, considers the development of standards for roiling bearing load/life ratings leading to ISO 281/1 due to be published this year. There is an interesting review of life adjustment factors with emphasis on the improvements which have been gained from developments in steel quality. The importance of inclusion content, especially alumina, on fatigue life is described along with the RHP approach to steel cleanliness assessment. The last paper by Mr G A W Setford of SPM describes the use of his company's shock pulse metering method for checking lubrication conditions in rolling bearings. The SPM method has been used for many years to monitor bearing condition, especially the onset of surface fatigue. The papers present information available elsewhere in one form or another and do not attempt a comprehensive approach to bearing selection. The practising engineer will find some useful information if he needs an introduction to the topics covered. He will not find full guidance on selecting bearings for economical and reliable designs. L G Hampson National Centre of Tribology, Risley, Warrington, UK,
225