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mittent current. The maximum ignition current is obtained when the circuit is first closed and the resistance unit on the rear end of the coil is cold. The current at this time is approximately 6 amperes, but soon decreases to approximately 31/2 amperes. Then as the engine is running it further decreases until at 1,000 revolutions of the engine it is approximately 1 ampere.
This motoring of the generator is necessary in order that the starting gears may be brought into mesh, and should trouble be experienced in meshing these gears, do not try to force them,
simply allow the starting pedal to come back, giving the gears time to change their relative position.
A clicking sound will be heard during the motoring of the generator. This is caused by the overrunning of the clutch in the forward end of the generator which is shown in view 1, Fig. 366.
The purpose of the generator clutch is to allow the armature to revolve at a higher speed than the pump shaft during the cranking operation and permitting the pump shaft to drive the armature when the engine is running on its own power. A spiral gear is cut on the outer face of this clutch for driving the distributor. This portion of the clutch is connected by an Oldham coupling to the pump shaft. Therefore, its relation to the pump shaft is
always the same and does not throw the ignition out of time during the cranking operation. This clutch receives lubrication from the oil that is contained in the front end of the generator which is put in at B (view 1). This is to receive oil each week sufficient to bring the oil up to the level of the oiler. The arrangement of clutch parts is shown at Fig. 367.
Q. Describe the "cranking” operation.
A. The cranking operation takes place when the starting pedal is fully depressed. The starting pedal brings the motor clutch gears (view 1) into mesh and withdraws the pin P (views 1 and 2),
allowing the motor brush switch to make contact on the motor commutator. At the same time the generator switch breaks contact. This cuts out the generator element during the cranking operation. As soon as
As soon as the motor brush makes contact on the commutator a heavy current from the storage battery flows through the series field winding and the motor winding on the armature. "This rotates the armature and performs the cranking operation. "The cranking circuit is shown in the heavy lines on the circuit diagram (Fig. 368). This cranking operation requires a heavy current from the storage battery, and if the lights are on during the cranking operation, the heavy discharge from the battery causes the voltage of the battery to decrease enough to cause the lights to grow dim. This is noticed especially when the battery is nearly discharged; also will be more apparent with a stiff motor or with a loose or poor connection in the battery circuit or a nearly discharged battery. It is on account of this heavy discharge current that the cranking should not be continued any longer than is necessary, although a fully charged battery will crank the engine for several minutes.
During the cranking operation the ammeter will show a discharge. This is the current that is used both in the shunt field winding and the ignition current; the ignition current being an intermittent current of comparatively low frequency will cause the ammeter to vibrate during the cranking operation. If the lights are on the meter will show a heavier discharge. The main cranking current is not conducted through the ammeter, as this
Fig. 368.—Wiring Diagram Showing Relation of Parts of 1916 Oakland-Delco Starting, Lighting
and Ignition System.
is a very heavy current and it would be impossible to conduct this heavy current through the ammeter and still have an ammeter that is sensitive enough to indicate accurately the charging current and the current for lights and ignition. As soon as the engine fires the starting pedal should be released immediately, as the overrunning motor clutch is operating from the time the engine fires until the starting gears are out of mesh. Since they operate at a very high speed, if they held in mesh for any length of time, there is enough friction in this clutch to cause it to heat and burn out the lubricant. There is no necessity for holding the gears in mesh.
Q. What is the “Delco” motor clutch for and how is it lubricated?
A. The motor clutch operates between the flywheel and the armature pinion for the purpose of getting a suitable gear reduction between the motor generator and the flywheel. It also prevents the armature from being driven at an excessively high speed during the short time the gears are meshed after the engine is running on its own power. This clutch is lubricated by the grease cup A, shown in view 1, Fig. 366. This forces grease through the hollow shaft to the inside of the clutch. This cup should be given a turn or two every week.
Q. How does the "Delco" machine deliver electric energy?
A. When the cranking operation is finished the motor brush switch is raised off the commutator by the pin P when the starting pedal is released. This throws the starting motor out of action. As the motor brush is raised off the commutator the generator switch makes contact and completes the charging circuit. The armature is then driven by the extension of the pump shaft and the charging begins. At speeds above approximately 7 miles per hour the generator voltage is higher than the voltage of the storage battery which causes current to flow from the generator winding through the armature in the proper direction to charge the storage battery. As the speed increases up to approximately 20 miles per hour this charging current increases, but at the higher speeds