Friction
The frictionless characteristics of ball and roller bearings are well known. While of little practical use in the actual bearing design, perhaps, it is interesting to compare the abilities of various types of bearings as measured by the coefficient of friction.
One of the outstanding differences between antifriction bearings and plain bearings, for example, is that the antifriction type will maintain an almost uniformly low coefficient of friction during wide variations in loading, whereas the plain bearing will under the same conditions exhibit a coefficient which varies greatly.
Another fact it is well to remember is that during non-operation of plain bearings the load or weight of parts generally forces out the oil, destroying the film on which its operating effectiveness rests, and since there is no rotation to build it up again, this leads to metal-to –metal contact and high starting friction in plain bearing machinery. Further, this momentary sliding contact between the metals in the plain bearing produces probably the greater portion of the total wear in a plain journal, as observed after a period of operation.
The friction characteristics of plain bearings are largely influenced by variation in the lubricating medium, and while anti-friction bearings do require a careful selection of lubricant, they are not nearly so sensitive to changes in type of characteristics.
As contrasted with the plain journal in which the oil is expelled during periods of inoperation, the anti-friction bearing presents rolling elements (either balls or rollers) between the load-carrying surfaces at all time, and therefore does not suffer from a similar action. The absence of this sliding friction at the start of operation has the effect of reducing the power required to start machines, and where a number of motors is involved this may be an item of considerable interest to the user.
Reliability
Anti-friction bearings could not have gained the widespread acceptance they have in the past few years without embodying the utmost reliability. Airplanes, railway cars of conventional and high-speed design, steel mill equipment, pulp and paper machinery, a great variety of machine tools, an almost unbelievable amount of textile machinery, mining equipment, delicate apparatus such as gyroscopes, signal relays, train control equipment – indeed an almost endless list of successful applications can be credited to anti-friction bearings. Coupled with this, the nationwide facilities of a great number of bearing companies make ball bearings readily available items. Replacement or rebabbitting of plain journals gives way to long, carefree service, and at economical costs.
Modern production and specialization has made almost every unit of apparatus vital in the accomplishment of a definite purpose, and each unit depending upon another must perform exactly as advertised. Reliability, therefore, is not a quality to be considered only in connection with a given piece or type of apparatus, but rather something that spreads over all industry. Throughout the processing of almost any manufactured article, or even raw material, the effect of anti-friction bearings can be observed today. In the deepest mines ball and roller bearings are permitting high efficiency and low cost. In the actual obtaining, handling, conveying, and delivery of raw material in steel mills almost every process depends to some extent on anti-friction bearings. In transportation in the air, on land, and on sea, they are contributing to the prompt and efficient dispatch of materials to thousands of manufacturing plants where more efficient machinery is delivering products of an endless variety to their respective fields of usefulness. In the textile field utilization of anti-friction bearings has been carried out to a remarkable degree. Millions of automobiles are creating records of economical performance from advantages obtained with anit-friction bearings. In power transmission, in the ventilating industry, in the paper industry and in many other specialized fields they are outstanding in their performance.
The frictionless characteristics of ball and roller bearings are well known. While of little practical use in the actual bearing design, perhaps, it is interesting to compare the abilities of various types of bearings as measured by the coefficient of friction.
One of the outstanding differences between antifriction bearings and plain bearings, for example, is that the antifriction type will maintain an almost uniformly low coefficient of friction during wide variations in loading, whereas the plain bearing will under the same conditions exhibit a coefficient which varies greatly.
Another fact it is well to remember is that during non-operation of plain bearings the load or weight of parts generally forces out the oil, destroying the film on which its operating effectiveness rests, and since there is no rotation to build it up again, this leads to metal-to –metal contact and high starting friction in plain bearing machinery. Further, this momentary sliding contact between the metals in the plain bearing produces probably the greater portion of the total wear in a plain journal, as observed after a period of operation.
The friction characteristics of plain bearings are largely influenced by variation in the lubricating medium, and while anti-friction bearings do require a careful selection of lubricant, they are not nearly so sensitive to changes in type of characteristics.
As contrasted with the plain journal in which the oil is expelled during periods of inoperation, the anti-friction bearing presents rolling elements (either balls or rollers) between the load-carrying surfaces at all time, and therefore does not suffer from a similar action. The absence of this sliding friction at the start of operation has the effect of reducing the power required to start machines, and where a number of motors is involved this may be an item of considerable interest to the user.
Reliability
Anti-friction bearings could not have gained the widespread acceptance they have in the past few years without embodying the utmost reliability. Airplanes, railway cars of conventional and high-speed design, steel mill equipment, pulp and paper machinery, a great variety of machine tools, an almost unbelievable amount of textile machinery, mining equipment, delicate apparatus such as gyroscopes, signal relays, train control equipment – indeed an almost endless list of successful applications can be credited to anti-friction bearings. Coupled with this, the nationwide facilities of a great number of bearing companies make ball bearings readily available items. Replacement or rebabbitting of plain journals gives way to long, carefree service, and at economical costs.
Modern production and specialization has made almost every unit of apparatus vital in the accomplishment of a definite purpose, and each unit depending upon another must perform exactly as advertised. Reliability, therefore, is not a quality to be considered only in connection with a given piece or type of apparatus, but rather something that spreads over all industry. Throughout the processing of almost any manufactured article, or even raw material, the effect of anti-friction bearings can be observed today. In the deepest mines ball and roller bearings are permitting high efficiency and low cost. In the actual obtaining, handling, conveying, and delivery of raw material in steel mills almost every process depends to some extent on anti-friction bearings. In transportation in the air, on land, and on sea, they are contributing to the prompt and efficient dispatch of materials to thousands of manufacturing plants where more efficient machinery is delivering products of an endless variety to their respective fields of usefulness. In the textile field utilization of anti-friction bearings has been carried out to a remarkable degree. Millions of automobiles are creating records of economical performance from advantages obtained with anit-friction bearings. In power transmission, in the ventilating industry, in the paper industry and in many other specialized fields they are outstanding in their performance.