Bearings and Their Applications

Related Resources: Design and Engineering General

Bearings and Their Applications

Bearing Applications, Specifications and Engineering

Bearings and Their Applications
Alex Weiss
2008
128 pages

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Open: Bearings and Their Applications

Introduction:

It is not easy to define exactly what constitutes a bearing. Clearly any machine that has a moving part connected to a stationary part will require a bearing between the two parts. The same is true for two moving parts that are connected together. For most people, rotating shafts are what spring to mind when thinking about bearings, but in many cases, such as a piston in a cylinder, or slides on a lathe, the two parts rub together in an oscillating linear motion and thus the interface between the two surfaces also needs to be thought of as a bearing. The materials used for their construction must be chosen with the same care as for a rotary bearing. Furthermore, both rotating and oscillating bearings may need to be made steam-, air-, oil- or waterproof by the use of a gland or stuffing box.

Bearings are hard-wearing anti-friction devices and the many different types have an array of anti-friction characteristics, wear rates, speed ranges and load-carrying capacities. As bearings have to permit smooth, low-friction movement between two surfaces, almost all employ some form of lubrication: either oil or grease. Bearings fall into two clear categories: rotary bearings, and linear or oscillating bearings. Both categories can further be divided into two distinct classes: those that use a sliding action and those that employ a rolling action. In either case, it is important to provide enough lubrication to keep the metal bearing surfaces separated by a film of oil or grease.

The absence of direct metal-to-metal physical contact allows most bearings to operate satisfactorily for long periods with minimal wear. Metal shafts running in plastic bearings are an exception to this requirement and many can operate without any lubrication.

Ball, roller and needle bearings are all based on the use of rolling elements: balls in the first case, rollers in the other two. Plain bearings, on the other hand, rely on a sliding action. They tend to be less expensive than rolling-element bearings and, of course, can readily be made in the model-engineer's workshop. They do, however, result in higher levels of friction and, all other things being equal, will not last as long as rolling bearings. A bush is often used as a bearing; this is a cylindrical sleeve that can be inserted to provide a bearing surface for a shaft or just for a pin.

Content:

Acknowledgements ix Introduction 1
What is a bearing? 1
Early bearings 2
Bearing loads 4
Bearing materials 4
Bearing layout problems 6
Bearing size 8
Imperial v. metric bearings 8
About this book 8

Chapter 1.
Plain bearings 11
Introduction 11
Bearing materials 11
Wood 11 Metal 12
Plastics 16
Making plain bearings 17
Bearing finish 18
Single-piece bearings 18
Bushes 20 Split bearings 20
Re-metalling bearings 21
Thrust collars 23
Glands and stuffing boxes 24
Hinges and pivots 25

Chapter 2.
Ball and roller bearings 27
Introduction 27
Ball bearings Manufacture 29
Cages 30
Shields and seals 30
Types 31
Angular-contact ball bearings 31
Self-aligning ball bearings 32
Thrust ball bearings 32
Lazy Susan bearings 33
Miniature ball bearings 33
Other ball bearing configurations 33
Roller bearings 33
Tapered roller bearings 34
Self-aligning roller bearings 35
Needle bearings 36
Fitting bearings 37
Bearing pre-load 39
Two-part roller bearings 41
Bearing problems and solutions 41
Obtaining bearings 42

Chapter 3.
Linear and oscillating bearings 43
Introduction 43
Cylinders, pistons and piston rings 44
Cylinders 44
Pistons and rings 45
Hot-air engines 48
Crossheads 48
Steam valves 49
Glands 49
Axle boxes and horn blocks 50
Internal-combustion engine valves 50
Slides and gib strips 51
Vices 52
Shock-absorbers and oleos 52
Linear-positioning devices 53
Lead and ball screws 53
Linear-motion slides

Chapter 4.
Other types of bearing 55
Introduction 55
Sintered bearings 55
Plummer or pillow blocks 56
Swash plates 57
Slipper bearings 58
Spherical bearings and rod ends 59
Coned-pivot and jewelled bearings 60
Cone-bearing lathes 60
Plastic ball bearings 62
Ceramic ball bearings 63
Wankel engines and vane pumps 64
Rotary valves 65
Rotary internal-combustion engine valves 66
Carburettors 66
Rotary steam valves 67
Sleeve valves 67
Pivot or knife-edge bearings 68

Chapter 5.
Lubrication and seals 69
Introduction 69
Choice of lubricant 70
Oils 72
Greases 73
Application of lubrication 75
Sealed bearings 76
Self-lubricating bearings 76
Two-part roller bearings 76
Re-packing stuffing boxes and glands 77
Steam engines 78
Displacement and mechanical lubricators 79
Internal-combustion engines 80
Gas turbines 81 Gearboxes 82
Road and cross-country vehicles 82
Hot-air engines 82
Boats 83
Wooden models 83
Clock and watch bearings 83
Machine tools 84

Chapter 6.
Which type of bearing to use 85
Introduction 85
Easy to make 85
Cost and availability 86
Friction 86 Size 87
Load capacity 88
Speed capability 89
Temperature effects 89
Bearing retention 89
Fit and tolerances 90
Precision 90
Corrosion resistance 90
Dirt and dust resistance 91
Lubrication 91
Liquid and gas retention 91
Matching bearings in prototype 92
Expected operating life 92
Ease of installation, repair or replacement 93
What to purchase 93
Bearing suppliers 94
Conclusions 95

Chapter 7.
Modelling applications 97
Introduction 97
Steam-powered models 97
Locomotives and rolling stock 97
Traction engines 98
Other steam-powered road vehicles 98
Static steam engines 99
Hot-air engines 99
Internal-combustion engines 99
Gas turbines 100
Other models 101
Machine tools 101
Cars and trucks 101
Tanks and other tracked vehicles 101
Horse-drawn vehicles 102
Boats 103
Aircraft 104 Carousels 105
Artillery pieces 105
Robots 106

Chapter 8.
Full-size applications 107
Introduction 107
Machine tools 107
Clocks and watches 108
Scientific instruments 109
Balance scales 110
Electric motors 110
Commutators 111
Weather vanes and wind-generators 111
Mechanical musical instruments 112
Other full-size applications 112

Housing Hole Tolerance Classifications for Metric Radial Ball and Roller Bearings of ABEC-1 and RBEC-1 Tolerance Classes
Stainless Steel Bearings Stainless steel bearings are preferred where corrosion and chemical resistance are required.
Sprocket Center Distance for a Roller Chain of known Length Equation and Calculator
Tapered Roller Bearing Setting Methods
Thrust Ball Bearings Magnitude of Life Ratings Use the following equation to calculate the magnitude of life rating .
Thin Section Bearings Application Considerations There are three types of thin-section bearings: radial contact, angular contact, and four-point contact bearings.
Thrust Chart Thrust is a reaction force described quantitatively by Newton 's second and third laws .
Flat Thrust Plate Bearing Design Equation and Calculator Fluid thrust bearings contain a number of sector-shaped pads, arranged in a circle around the shaft, and which are free to pivot.
Step Thrust Plate Bearing Design Equation and Calculator
Tapered Land Thrust Plate Bearing Design Equation and Calculator
Tilting Pad Thrust Plate Bearing Design Equation and Calculator
Typical Bearing Life in hours for Various Design Applications