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ELEMENTARY ELECTRIC STARTER PRINCIPLES
Types of Self-Starters Defined—One Unit Systems—Two Unit Systems—
Three Unit Systems—Parts of Systems and Functions—Generator Types—Current Regulating Means—Methods of Cranking EngineStarting Switches—Indicators—Roller Clutches—Miscellaneous Devices.
ELECTRIC lighting, cranking and ignition systems for motor cars are of such recent development that it is not possible to describe all systems used for this purpose. Not only do the individual systems vary in detail, but the components of the same system are often of different construction when used on cars of different makes. The standard equipment must include three important functions, namely, the generator which is driven by the engine end which produces electric current to keep a storage battery charged, and the starting motor which is in mechanical connection with the engine and in electrical connection with the storage battery when it is desired to turn the engine over for starting. If the motor and generator are combined in one instrument the starting system is known as a one unit type. If the motor is one appliance and the generator another, the system is said to be a two unit system. Each of these has advantages, and both forms have demonstrated that they are thoroughly practical. In addition to the three main items enumerated, various accessories, such as switches, ammeters, connectors, wiring, protective circuit breakers, automatic current regulators, etc., are necessary for the convenient distribution and control of the electric current. The arrangement of the parts of a typical one unit system in which the motor-generator is used only for starting and lighting is shown at Fig. 139. This shows the location of the various parts in their relation to the other components of the motor car. The motor
generator is mounted at the side of the engine, and is driven by the magneto drive shaft as at A, Fig. 140, when used as a generator, and serves to drive the engine through this means when it is used as a motor. The ignition current is supplied from an independent source, a high tension magneto. The starting switch and that controlling the lighting system are placed on the dash, while the storage battery is carried under the floor of the tonneau. This system, which is known as the Entz, will be described more in detail in following chapter. Latest practice is to use the direct silent chain drive as at Fig. 140, B.
The elements of a one unit system are shown in diagram form at the left of Fig. 141. · It will be observed that the armature car
ries two commutators, one of which is used when the armature is driven by the engine and when the device serves as a current generator, the other being employed when the operating conditions are reversed and the electrical machine is acting as a motor to turn over the engine crankshaft. When the device is driven as a generator the small sliding pinion on the short end of the shaft is out of engagement with the spur gear cut on the flywheel exterior. When it is desired to start the engine the spur gear is meshed with the member cut on the flywheel and the current from the storage battery is directed to the windings of the electric machine which becoming a motor and which turns over the engine
crankshaft. When the device is working as a generator the current that is developed goes to the storage battery, and from that member to the various current consuming units.
Sometimes the motor and generator are combined in one casing and the system so provided is erroneously called a "one unit” system. This construction is shown at the right of Fig. 141. In reality such a system is a two unit system, because the electrical machines are uni-functional instead of performing a dual function as does the combined-motor-generator at the right of the illus
Unit Starting System to Motors of Conventional Design.
Application of one
Fig. 141.-Simplified Diagram Showing Operation of One Unit System at
A and Two Armature One Unit System at B.
tration. The wiring of the one unit system is shown in simplified form and should be easily followed by any repairman. The parts of a two unit starting and lighting system are shown at Fig. 142. This system is sometimes called a “three unit” system, on account of having a source of independent current supply for ignition purposes. This is shown as fitted to the Overland six-cylinder engine at Fig. 143. As will be observed, the generator in the diagram is driven from the motor crankshaft by silent chain connections, one of the terminals passing through the eut-out device
and to the storage battery, the other terminal running directly to the storage battery terminal having a short by-pass or shunt wire attached to the cut-out. All the time that the engine is running the generator is delivering electricity to the storage battery.
It will be seen that the storage battery is also coupled to the lighting circuits which are shown in a group at the right of the illustration, and to the electric starting motor as indicated. One of the storage battery terminals is joined directly to the switch
terminal by a suitable conductor, the other goes to one of the terminals on the starting motor, while the remaining terminal of the starting motor goes to the switch. In this system, when the small sliding pinion is meshed with the flywheel gear, the switch is thrown on simultaneously, and the current that flows from the storage battery through the windings of the starting motor rotates the engine crankshaft by means of reduction gears shown. As soon as the engine starts the foot is released and a spring pulls the switch out of contact, and also disengages the sliding pinion from the flywheel gear.