Lubricant

“ Hence in the case of lubrication the velocities of the fluid at the surfaces of the solids are those of the solid. In as far as the presence of the lubricant is necessary, such properties as cause oil in spite of its surface tension to spread even against gravity over a bright metal surface, while mercury will concentrate into globules on the bright surface of iron, have an important place in securing lubrication where the action is intermittent, as in the escapement of a clock. ”

“ The lubricant, owing to its viscosity, is forced between the surfaces and keeps them entirely apart. This property of viscosity is one of the most important possessed by liquid lubricants. Some lubricants, such as the oils used for the light spindles of textile machinery, are quite thin and limpid, whilst others, suitable for steam engine cylinders and very heavy bearings, are, at ordinary temperatures, as thick as treacle or honey. ”

“ The pressure that can be borne by a good lubricant for a useful length of time depends upon the nature of the bearings as well as upon the lubricant itself. The velocity of the rubbing action also must be taken into consideration. The maximum of pressure that solid lubricants will bear without destruction is unknown. For steel surfaces, lubricated with best sperm oil moving slowly, 1,200 lbs. pressure per square inch of bearing surface has been found permissible. Under the pivots of swinging bridges several thousand pounds per square inch have been found to work, and for iron journals 800 lbs. ”

“ An oil having little viscosity is suitable for the escapement and lighter parts of the train, but is not a good lubricant for the bearings of the center pinion and barrel arbor and the mainspring, which require a more viscous lubricant ”

“ If some of the bearings need a small quantity of oil, being otherwise in such good condition—because of never having been used, in fact "new"—that it is unnecessary to take all the mechanism apart and clean it, it is very important that the operator know what kind, or variety, of lubricant has been previously used, in order not to "mix oils;" ”

“ Liquid lubricants are used for all high speed bearings. In some cases the rubbing surfaces work in a bath of the lubricant, which can then reach all the rubbing parts with certainty. Small engines for motor cars or road waggons are often lubricated in this way. In the case of individual bearings, such as those of railway vehicles, a pad of cotton, worsted and horse hair is kept saturated with the lubricant and pressed against the under side of the journal. The journal is thus kept constantly wetted with oil, and the film is forced beneath the brass as the axle rotates. ”

“ If the bearing is set so tight that there is no room for the interposition of an oil film, the shaft and journal will at once heat. The greater the pressure of the shaft in its box, the thicker, or heavier, should be the lubricant used, for a light oil would be squeezed out or "broken down" more easily than would one that possesses greater viscosity. ”

“ Testing for Salts and Acids, etc.—It will be obvious that however good as a lubricant an oil is, and however valuable its properties may be when examined, if it possesses any corrosive quality which will be injurious to the metals upon which it is placed, it will soon become detrimental to the machinery, and may also cease to be valuable as a lubricant. ”

“ Generally speaking, the greater the viscosity of the lubricant the greater the load the bearing will carry, but with thick lubricants the frictional coefficient is correspondingly high. True lubricants differ from ordinary liquids of equal viscosity inasmuch as they possess the property of “oiliness.” This is a property which enables them to maintain an unbroken film between surfaces when the loads are heavy. It is possessed most markedly by vegetables and animal oils and fats, and less markedly by mineral oils. ”

“ There is great diversity in the shapes of rubbing surfaces, the loads they have to carry vary widely, and the speed of rubbing ranges from less than one foot to thousands of feet per minute. There is also a large number of substances which act as lubricants, some being liquids and others soft solids. In many instruments or machines where the surfaces in contact which have to slide upon each other are only lightly pressed together, and are only occasionally given relative motion, the lubricant is only needed to prevent abrasion. ”

“ In such cases, the lubricant which keeps the surfaces from abrading each other is a mere contamination film, either derived from the air or put on when the surfaces are finished. When such lubricating films are depended upon, the friction surfaces should be as hard as possible and, if practicable, of dissimilar metals. In the absence of a contamination film, most metals, if rubbed when in contact, will immediately adhere to each other. A large number of experiments have been made to ascertain the coefficient of friction under these imperfect conditions of lubrication. ”

“ The less the viscosity, consistently with the use of the oil under the maximum pressure to be anticipated, the less is, usually, the friction. The best lubricant, as a rule, is that having the least viscosity combined with the greatest adhesiveness. Vegetable oils are more viscous than animal, and animal more so than mineral oils. The fluidity of an oil is thus, to a large extent, a measure of its value. ”

“ Mineral Oil (11) has been used as a lubricant for time keeping mechanism; but as there are so many varieties on the market, each differing from the others and possessing properties peculiar to itself, and as many have made experiments which have not demonstrated that such oils possess all the essential qualities of a perfect lubricant in horology, the author believes that the abundance of kinds and qualities of mineral oils has in the past been more or less confusing to the majority of those who have experimented ”

“ Liquid lubricants, such as sperm oil, or one of the products of petroleum, the latter medium being the class of lubricant most suitable for internal combustion engines, owing to its combining the qualities of a high flash-point with a comparative freedom from either acidity or causticity.
Oils of animal or vegetable origin should never be used with gas engine as the high temperatures encountered will char and render them useless. Tallow and lard oil are especially to be avoided, at least in a pure state. ”

“ Lubricants Used for Turning.—A good grade of lard oil is an excellent lubricant for use when turning steel or wrought iron and it is extensively used on automatic screw machines, especially those which operate on comparatively small work. For some classes of work, especially when high-cutting speeds are used, lard oil is not as satisfactory as soda water or some of the commercial lubricants, because the oil is more sluggish and does not penetrate to the cutting point with sufficient rapidity. ”

“ Turret lathes and automatic turning machines are equipped with a pump and piping for supplying cooling lubricant to the tools in a continuous stream. Engine lathes used for general work, however, are rarely provided with such equipment and a lubricant, when used, is often supplied by a can mounted at the rear of the carriage, having a spout which extends above the tool. Owing to the inconvenience in using a lubricant on an engine lathe, steel, as well as cast iron, is often turned dry especially when the work is small and the cuts light and comparatively short. ”

“ If possible, lubrication by oil should be substituted by grease lubrication through screw caps.
Particular attention should be paid to the back of the machines. None but the individual in charge of engines should be allowed to lubricate the machines, and he should be held responsible for any excess of lubricant.
As a rule oil-marks are restricted to the edges or the proximity of the edges of crepe, but sometimes the streak is to be found in the middle of the length. In such a case it is almost certain [227] that the oil or grease has been picked up by the rubber in the tray. ”

“ Heavy and inferior oils have a tendency to carbonize quickly, also “gum up” the piston rings, valve stems and bearing. In cold weather a light grade of oil having a low cold test is absolutely essential for the proper lubrication of the car. The nearest Ford branch will advise you concerning the lubricating oil this company has found best suited for its cars, both for summer and winter weather. Graphite should not be used as a lubricant in the engine or transmission as it will have a tendency to short circuit the magneto. ”

“ The only oil which is said to have no action on rubber, or practically none, is castor oil; all the same, I do not advise its use as a lubricant.
There are three only which we need consider:—
1. Soda and water. 2. French chalk. 3. Pure redistilled glycerine. ”

“ If, with the gears in neutral, the engine cranks over hard, it indicates a lack of lubricating oil, or a lack of water, which has allowed the engine to reach a temperature where the lubricant fails to perform its work. ”

“ Lubrication is faulty when the quantity of lubricant supplied is either insufficient or too abundant, or when the oils employed are of bad quality. It has already been shown that insufficient lubrication and the utilization of bad oils leads to the overheating of the moving parts. ”

“ Revolving wire lubricator; carries a drop of oil on to the shaft at each revolution.
973. Roller and pan lubricator. Can be employed also for gum, paste, paint, &c.
974. Screw ram lubricator, to force lubricant into a cylinder or pipe against pressure, with non-return valve.
975. Telescopic tube lubricating device, for reciprocating or revolving joints, such as crank pins.
976. Another tubular device for crank pins; a hollow cup on end of a tube stands opposite the centre of the shaft, and can be fed with oil while revolving, the oil running down the tube during the lower half revolution. ”

“ Mechanically operated or pressure lubricators supply oil to all parts of the engine, and as the quantity passed to each bearing is adjustable, a feed may be maintained that is exactly suited to the requirements.
The bearings of an automobile operate under such widely different conditions that one kind of lubricant will not be suitable for all. The maker of the car has tested the different oils, and it is advisable to follow his instructions on the brand and grade most suitable for each bearing, rather than to try experiments. ”

“ The transmission and differential operate more successfully when a lighter grade of grease is used, such as a graphite compound, or a heavy oil known as 600 W.
Oils.—Great care should always be exercised in purchasing lubricants. None but the best grades should be considered under any circumstances. The cheaper grades of oil will always prove to be the most expensive in the end. The ordinary farm machinery oils should never be used in any case as an engine lubricant, for in most cases they contain acids, alkalies, and foreign matter which will deteriorate and destroy the bearings of the motor. ”

“ Every properly-lubricated portion of a motor either moves in a bath of oil or is connected with an oil reservoir so that a certain amount will be fed regularly to the rubbing surfaces. There is always some heat generated in a bearing, no matter how well it may be lubricated, and the continuous flow or circulation of the oil serves to carry off this heat that would otherwise tend to dry the lubricant if there were no fresh supply.
The proper lubrication of the motor is even more necessary than is the adjustment of the carburetor or the condition of the ignition system. ”

“ Liquid Lubricants.—Generally speaking, all bearings which it is necessary should run with as little friction as possible must be supplied with liquid lubricants. These may be of animal, vegetable or mineral origin. The mineral oils are mixtures of hydrocarbons of variable viscosity, flashing-point, density and oiliness. They are obtained by distillation from American, Russian and other petroleums. The fixed oils obtained from animal and vegetable substances are not volatile without decomposition, and are found ready made in the tissues of animals and plants. ”

“ For instance, some thin mineral oils were found to be quite as valuable as, and in some cases superior to, sperm; and this was caused by the lips on the sides, which prevented the oil from running off the bearing when an increased fluidity was caused by friction, and by any slight elevation of temperature. This is a very important quality in lubricating oils, probably next to the capacity to resist oxidation, the most important to be criticised by those who wish to value a lubricant. ”

“ But a true cylindrical journal swims in an oil-bath, separated from its bearing at every point by a film of oil of uniform thickness, and sustaining a uniform pressure, which cannot [160] be anywhere broken, and which has very little inclination to work out; and if it revolves without deflection and the pressure per square inch of surface is not sufficient to press out the lubricant, the speed is absolutely immaterial and wear is impossible, except that due to the attrition of the oil itself, which on hardened surfaces has no appreciable effect. ”

“ In the case of fats and greases whose melting points are not much above the temperature of surrounding objects it generally happens that the lubricating films are so warmed by friction that they actually melt and act as oils. These lubricants are generally forced into the bearings by a form of syringe fitted with a spring piston, or are squeezed between the faces by means of a screw-plug. ”