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and carries a double winding of wire which consists of two coils, one of coarse, the other of fine conductor. The armature is attached to end pieces which carry shafts and the whole assembly revolves on annular ball bearings. An ebonite or hard rubber spool is carried at one end while the condenser is housed at the other. The make-and-break mechanism is partly carried by an oscillating casing and the revolving member is turned from the armature shaft. The current generated in the armature coils is delivered to a metal ring on the ebonite spool, from which it is taken by a carbon brush and delivered directly to the spark plugs. Every time the contact points in the make-and-break device become separated, a current of high potential passes through one of the wires attached to the spark plugs and produces a spark between its points. The magneto is the simplest and most practical form of ignition appliance, as it is selfcontained and includes the current generator and the timing device in one unit. In the one-cylinder form all connections are made inside of the device and but one wire leading to the spark plug is necessary to form the external circuit. A magneto employed for multiple-cylinder ignition is not much more complicated than that used for single-cylinder service, the only difference being that a different form of cam is provided in the breaker box and that a secondary distributor is added to commutate the current to the plugs in the various cylinders. The distributor consists of a block of insulating material fixed to the magnets which carries as many segments as there are cylinders to be fired. A central distributing arm or segment is driven from the armature shaft by means of gearing and is employed to distribute the high-tension current to segments connected to the spark plugs in the cylinders by flexible wire conductors. A typical magneto ignition system such as used on Maxwell cars is shown at Fig. 14.
How Engine Is Lubricated.—The importance of minimizing friction at the various bearing surfaces of machines to secure mechanical efficiency is fully recognized by all mechanics, and proper lubricity of all parts of the mechanism is a very essential factor upon which the durability and successful operation of the
Fig. 15.–Sectional View of Crank Case of Maxwell Four Cylinder Engine, Showing Typical Constant
Level Splash System of Lubrication.
motor car power plant depends. All of the moving members of the engine which are in contact with other portions, whether the motion is continuous or intermittent, of high or low velocity, or of rectilinear or continued rotary nature, should be provided with an adequate supply of oil. No other assemblage of mechanism is operated under conditions which are so much to its disadvantage as the motor car engine, and the modern tendency is toward a simplification of oiling methods so that the supply will be ample and automatically applied to the points needing it.
In all machinery in motion the members which are in contact have a tendency to stick to each other and the very minute projections which exist on even the smoothest of surfaces would have a tendency to cling or adhere to each other if the surfaces were not kept apart by some elastic and unctuous substance. This will flow or spread out over the surfaces and smooth out the inequalities existing which tend to produce heat and retard motion of the pieces, relative to each other. The method of supplying the lubricant will depend largely upon the nature of the part to be oiled as well as the character of the oily medium.
The various internal parts of the gasoline engine demand continual lubrication and means must be provided which will insure positive supply of lubricant in measured quantities for more or less extended periods. Engine' lubricators should be positive in action and not liable to be affected by varying weather conditions. The lubricant should not be supplied in excess and in some systems it is desirable that the feeds be adjusted as desired and independently of each other. Any oiling device should be as nearly automatic in action as possible and the modern types should require but little further attention from the motorist than to keep a proper amount of lubricant in the container. The oil feed to the moving parts should start as soon as the engine begins to turn and the supply be interrupted when the mechanism stops. The only system which combines all the desirable features is that which includes a mechanical drive from the source of power. Lubricators may be divided into two classes, those which depend upon natural phenomena such as attraction of gravity or displacement of air pressure
Fig. 16.—Part Sectional View of Dort Four Cylinder Unit Power Plant, Showing Important parts of
Motor, Clutch and Change Speed Gearing,
and others which are worked by mechanical means and which deliver the oil in measured quantities by positively driven pumps. The former are never used now on automobile engines, as reliability is essential without calling for constant attention.
Oil Supply by Constant Level Splash System.—The splash system of lubrication that depends on the connecting rod to distribute the lubricant is one of the most successful and simplest forms if some means of maintaining a constant level is provided. If too much oil is supplied the surplus will work past the piston rings and into the combustion chamber, where it will burn and cause carbon deposits. Too much oil will also cause an engine to smoke and an excess of lubricating oil is usually manifested by a bluish white smoke coming from the exhaust pipe. A good method of maintaining a constant level of oil for the successful application of the splash system is shown at Fig. 15. The engine base casting has a separate chamber attached to it which serves as an oil container and which is below the level of oil in the crank case. The lubricant is drawn from the sump or oil container by means of a positive oil pump which discharges directly into the troughs under each connecting rod in the engine base. The level is maintained by an overflow which allows all excess lubricant to flow back into the oil container at the bottom of the engine base. Before passing into the pump again the oil is strained or filtered by a screen of wire gauze and all foreign matter removed. Owing to the rapid circulation of oil it may be used over and over again for quite a period of time. New oil is introduced directly into the crank case by a breather pipe and the amount available is indicated by a simple gauge.
Power Transmission Parts.—A typical power transmission group such as employed in the Dort gasoline automobile is depicted in Fig. 16. In this the power is applied to the crankshaft of the motor and from thence it is delivered to the motor flywheel which forms the female member of a friction clutch. The male member of the clutch is coupled to the change speed gearing and this in turn is joined to the driving pinion in the rear axle by a length of shaft not shown in the illustration.