1942 - 1947 Chevrolet Shop Manual



	12-19

	ground. This will operate the generator as a motor. The ammeter reading, with the generator running, should be from 4 to 6 amperes. When motoring voltage regulated generators, make sure to connect the positive of the battery to the positive terminal of the generator, otherwise the residual magnetism of the generator will be reversed, thereby reversing the polarity of the generator. After overhauling a voltage regulated generator, the voltage setting and the generator output (amperage) should be checked on the car or truck as described earlier in this section. NOTE—It is good practice, after reassembling a generator on the car or truck, to use a juniper lead to momentarily connect the battery terminal of the regulator with the generator terminal. This sends a current through the generator windings, assuring that if will build up in the proper polarity. THE STARTING SYSTEM The starting system has only one function to perform—to crank the engine. In the starting system, there are three units: the battery, the starting switch and the starting motor, Fig. 41.	THE STARTING MOTOR The starting motor is similar in construction and appearance to the generator, but the design of the parts is different. Both motor and generator require frame, field coils, armature, brushes, etc. The operation of the starting motor is the reverse of the generator. In the case of the generator, a loop of wire is revolved in the magnetic field and generates current. In the case of a starting motor, current is supplied to the loop which lies in a magnetic field. As the loop rotates, mechanical energy is produced. The starting motor is designed to incorporate a manual shift drive mechanism which assures positive engagement of the starting motor pinion with the flywheel until the engine is started, Fig. 42. This is of particular benefit when starting a cold engine, as the starting motor will continue to crank the engine as long the the driver depresses the starter pedal. In this design, the starter pinion in conjunction with an over-running clutch (or roller clutch), a compression spring and pulley-like sheave are mounted as an assembly on the splined part of the armature shaft. The sheave and spring are mounted to rotate freely on the outer diameter of the tube portion of the assembly. Fig. 42.


	Fig. 41-Starting Motor Circuit The battery supplies the energy, the switch completes the circuit, allowing this energy to flow to the starting motor. The motor then delivers mechanical energy and does the actual work of cranking the engine. The starting equipment is used for a short time only and then remains idle until it is again needed to start the engine. The battery, however, performs other functions. It should be noted that the starting motor draws a large amount of current for a short period of time, whereas the generator replaces this current by charging the battery at a lower rate for a much longer period of time.
		Fig. 42-Cut-Away View of Starting Motor Drive A multiple spring and roller over-running mechanism, Fig. 43, similar to that of a bicycle coaster brake, is located between the outer part of the clutch which is attached to the pinion and the inner part splined to the armature shaft.