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portant bearing-points of the car to which it can be applied with a hand oil can or syringe. Instead of throwing away the oil it is possible to save quite a few gallons in the course of a year, if the simple filtering device as shown at Fig. 223 is used. This may be made up by any tinsmith at small cost. It consists of a main container of galvanized iron having a tight-fitting cover so dirt will not get into it. Three ledges are soldered to the sides of the tank as indicated, the one at the top holding a brass wire gauze
screen, the two lower ones acting as supports for funnels. The discharge opening of
each funnel is filled Rings
with clean waste, and by the time the oil reaches the bottom of the container it has been thoroughly fil
tered, the larger parPetcock
ticles of dirt being restrained by the brass screen, while the re
mainder is held by the Fig. 223.-Easily Made Oil Filter for Garage Use.
waste plugs. A pet
cock is soldered to the bottom of the tank, so the filtered oil may be drawn out as needed.
Requirements of Lubricating Oils.—Much difference of opinion exists relative to the best grade of lubricating oil to use in the automobile power plant, some repairmen favoring the use of a very light, free flowing oil, others recommend oils of medium body. The best oil to use depends entirely upon the type of power plant and closeness of fit between the parts of the mechanism; no one grade of oil is suitable for all engines. The following extract from a paper read by Harry Tipper, an authority on lubricants and lubrication, before the S. A. E., outlines the points involved in the selection of a suitable lubricating medium very clearly, and may be read with profit by all motorists and repairmen.
“Inasmuch as the arbitrary tests to determine the physical characteristics of the oil do not illuminate its value for any particular purpose, let us consider what the oil should do. In order to bring this directly to the point of greatest interest to the society, that is, the lubrication of the motor of automobiles, let me suggest the requirements which a lubricant for this purpose should meet :
1. The oil should possess a sufficient body to keep the bearing surfaces apart at the temperature at which the bearings run.
2. It should possess such qualities as will reduce the friction to a minimum.
3. The flash point should be sufficiently high to insure against the presence of volatile constituents.
4. It should remain fluid at such low temperatures as will be met in service conditions.
5. It should have no tendency to decompose or to form such deposits as will gum up the machine and increase the friction, where the object is to decrease it.
6. It should contain no ingredients which will corrode or pit the metal.
"In considering the qualifications to be added to these general requirements in order to define application to the mechanical conditions of cylinder lubrication, it is necessary to consider the questions involved in the operation of an internal combustion engine, which are different from those of any other type. What I have to say now may appear very elementary from a mechanical standpoint, but unless it is mentioned, the important bearing which it has upon lubrication will not be as obvious as I want to make it. After a charge has been taken into the cylinder on the suction stroke it is compressed to from 50 to 75 pounds before being fired. Naturally upon the starting of the compression stroke there is a tendency for the gasoline mixture to leak. There are two ways of obviating this difficulty, of securing full compression. These two ways might be stated as mechanically secured compression, formed by the close fit between the piston or piston rings and the cylinder wall; or compression secured by liquid seal, which means the use of an easy clearing between the piston rings and the
cylinder wall and the sealing of the space between them by the use of a proper kind of lubricating oil. In respect to the mechanically secured compression the following points are worth noting as axioms which must be taken into consideration in estimating the conditions:
1. The closer the fit, that is, the less the clearance between the piston and cylinder walls, the more the power absorbed in turning the engine over. In fact, it is possible to secure perfect compression in this way only by securing so tight a fit that the mechanism will not turn. Even in practice good compression can be secured only at the sacrifice of some of the effective power.
2. The closer the mechanical fit between piston and cylinder walls the thinner a lubricating oil which will work its way between them. The thinner the lubricating oil the greater will be the wear and tear, because of the impossibility of keeping the metal surfaces apart where the clearances are so small and the lubricant must be such a slight film.
“With these conditions, when wear and tear has once begun, every stroke of the engine increases the loss of compression, the consumption of lubricating oil, the consumption of gasoline, in proportion to the amount of power, and, in fact, decreases continually the efficiency of the motor. You will readily see the impossibility of securing and maintaining maximum efficiency under the conditions. The motor after leaving the factory is run at great variations of speed and considerable variation of load.
These variations are quite rapid and frequent. On account of the mechanical conditions of the motor you have recommended a very thin, light lubricating oil for the motor, under the guarantee. This lubricating oil has no particular adhesiveness and will flow as readily from the cylinder wall as to it. Consequently, during the rapid and frequent variations of speed, cylinder walls are sometimes overburdened with oil and sometimes practically dry, making wear and tear excessive and naturally resulting in a very rapid increase in the space between the piston and cylinder wall. This wear and tear is not thoroughly even; the clearance is larger in some places than in others. Then the lubricating oil flows freely up and down the walls of the cylinder and there is never any time
when just the proper amount of oil is on the cylinder wall. The oil is so thin that it cannot be held in the increased space, consequently on the compression stroke the gasoline mixture escapes past the piston, destroying the lubricating oil in the crankcase, and reducing from 15 to 30 per cent. the power which should be secured from the gasoline. Further, the condition under discussion is responsible largely for the carbon which is so constantly being experienced on account of the fact that the oil, being very light in body and free-flowing, is drawn up during the suction stroke into the compression chamber and onto the piston head, where it is distilled, leaving a coke baked on the piston head to the first ring, upon the valves, etc.
“Consider, instead of the mechanically secured compression used in connection with thin oil, compression which depends upon the use of lubricating oil, the clearances being larger. From the standpoint of the mechanical efficiency of any power generator, and, in fact, any moving equipment, the best fit-that is, the mechanical fit which absorbs the least amount of power due to friction in the power generator itself—is an easy sliding fit. If dependence is to be laid, however, upon the metal and not upon the lubricating oil to maintain compression, this easy sliding fit is too loose to give the compression required. If, however, it is intended to secure the compressicn by the liquid seal of the lubricant, then an easy sliding fit can be given to the motor, a sufficiently heavy-bodied oil used for lubricating with the result that the metal surfaces can be kept apart, the compression can be maintained so that there will be practically no change in the lubricating oil in the crankcase, and only the ordinary wear and tear on a properly lubricated surface will take place, which wear and tear is infinitely slower than the wear and tear which usually occurs under the conditions previously mentioned. In working out lubricating cls for automobile engines we are using to-day oil of 200, 300, 500 and 750 viscosity; the oil of 200 seconds viscosity being used entirely for those motors which are being made with clearances too small to permit of the oil of the proper body being used. Thousands of tests by private owners, which, while they may not be accurate, indicate the general result that in practice by the use of these
heavier oils they have secured from 10 per cent. to 20 per cent. and in some cases over 30 per cent. more power from the fuel, cwing to the saving of any loss on the compression stroke. On this account they have also used less lubricating oil, due to the fact that there is no admixture of gasoline, deterioration consequently being very slow. There is also less wear and tear on the cylinders and practically no trouble from carbon."
Peculiar Cause of Overheating.-A motorist who owned a very good make of car was bothered by a particularly severe case of overheating, and was at a loss to find its true cause. The motor was thoroughly overhauled to make sure that the lubricating system was functioning properly, the interior of the waterjackets was cleared of all incrustation, the radiator replaced by one of larger capacity, the pump and water piping examined to insure that the water circulation was brisk, the exhaust valves gone over to make sure that they lifted enough to release the gases and that they opened early enough, and all important members in the transmission system were inspected to see that there was no binding or harsh action at these points that would absorb power. Despite all the precautions taken, the car continued to overheat and nothing the local repairman could do prevented the trouble. The writer was finally asked to give an opinion, and after the various remedies that had been applied ineffectually had been described in detail, it seemed that but little had been overlooked, and the case assumed that mysterious aspect that often puzzles even the most expert of repairmen.
The car was not fitted with a muffler cut-out valve and the writer noticed that the muffler seemed particularly efficient as regards silence, a barely perceptible sound being heard as the gas was discharged in the air. As the overheating was accompanied by loss of power, and as the engine had very little power even when cooled it was assumed that the overheating was due to some condition of the mixture, but varying this till it was so thin that the engine backfired through the carburetor did not improve either the power or the chronic overheating. As an experiment, the muffler was removed and the car operated with a direct exhaust. The result was a revelation, as the car not only had all the power