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Bearings and Their Lubrication
Bearings and Their Lubrication
L. P. Alford, M. E.
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The aim of this book has been two fold; to present the underlying principles involved in the design of all classes of machinery bearings and to show modern practice in the construction and application of important commercial types. It is believed to be the first treatment of these subjects ever put into book form.
The tendency of modern machine design in many fields is toward the use of high speed shafts and spindles and friction reducing forms of bearings. Therefore the present seems a peculiarly fitting time to present these data with the purpose of making them permanently useful to engineers, designers, draftsmen and machinists; in fact to any one who is interested in any way with machinery bearings and their proper lubrication and care. Many of the data have never before been published in any form.
Many of the experiments and researches quoted are from European sources and official transactions of technical societies and are not generally known to American readers.
It is a pleasure to acknowledge the many courtesies received from engineers and machinery manufacturers and the valuable information furnished by them. Without this hearty cooperation it would have been impossible to have produced this work. L. P. Alford.
Machinery bearings are the parts of the bed, frame or other members that constrain rotating parts, such as shafts and spindles. They are divided into two general classes, journal and thrust, depending upon the direction in which the load acts. In the journal bearing the load acts at right angles to the axis; in thrust bearings, parallel to the axis.
The bearing surface of all journal bearings is necessarily circular in cross- section. In profile it is ordinarily cylindrical, but may be conical, spherical or even of a more complicated shape. The bearing surface of thrust bearings is ordinarily flat, but may be spherical, conical, or shaped to the curve of the tractrix.
Bearings are also divided into two classes by the kind of contact between the surfaces; that is, bearings having sliding contact, or ordinary bearings, and bearings having rolling contact or ball and roller bearings.
The bearing surfaces of ball bearings both radial (journal) and thrust are ordinarily curved races with a circular cross-section. Less commonly the surfaces are flat.
The bearing surfaces of journal roller and thrust bearings are circular in cross-section and either cylindrical or conical in profile.
The accompanying table gives a classification of machinery bearings. Flat constraining surfaces for sliding machine parts having rectilinear movements have no common name, but are referred to as ways, guides, and the like.
The relative motion of all these constraining members and the members constrained is resisted at their surfaces of contact by a force which is called the force of friction. Thus, all kinds of bearings must be designed with particular reference to minimizing this force, and our starting-point must be a study of friction.
Classification of Machinery Bearings
BEARINGS WITH SLIDING CONTACT
I. Sliding Friction 5
II. Coefficients OF Friction OF Journal, Collar, Step AND Guide Bearings . . 31
III. Materials for Bearings 41
IV. Allowable Pressures, Speeds and Temperatures 65
V. Design of Journal Bearings 86
VII. Design of Flat Sliding Surfaces and Special Bearings 132
VIII. Three Important Bearing Inventions 139
IX. Typical Designs and Constructions 141
X. Hints on the Care of Bearings 166
PART II BEARINGS WITH ROLLING CONTACT
I. Rolling Friction and Factors of Design 173
II. Construction of Ball Bearings 180
III. Typical Designs and Mountings for Ball Bearings 195
IV. Lubrication of Ball Bearings 204
V. Roller Bearings with Flexible Rollers 209
VI. Radial Roller Bearings with Solid Rollers 217
VII. Roller Thrust Bearings 221
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