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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 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. 173). 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 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 are 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.

Motor Clutch.—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. 171. This forces grease through the hollow shaft to the inside of the clutch. This cup should be given a turn or two every week.

Generating Electrical Energy.- 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 approxi. mately 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 the charging current decreases. The curve, Fig. 173, shows approximately the charging current that should be received for different speeds of the car. There will be slight variations from this due to temperature changes and condi. tions of the battery which will amount to as much as from 2 to 3 amperes.

Lubrication.—There are five places to lubricate this Delco System. No. 1-The grease cup for lubricating the motor clutch (D, view 1, Fig. 171). No. 2-Oiler for lubricating the generator clutch and forward armature bearing (B). No. 3—The oil hole (C) for lubricating the bearings on the rear of the armature shaft. This is exposed when the rear end cover is removed. This should receive oil once a week. No. 4—The oil hole in the distributor, at A, for lubricating the top bearing of the distributor shaft. This should receive oil once a week. No. 5—This is the inside of the distributor head. This should be lubricated with a small amount

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Fig. 174.—Curves Showing Output of Delco Generator No. 69 at Different Car Speeds.

of vaseline, carefully applied two or three times during the first 2,000 miles running of the car, after which it will require no attention. This is to secure a burnished track for the rotor brush on the distributor head. This grease should be sparingly applied and the head wiped clean from dust and dirt.

Delco Voltage Regulator.-In the 1914 Delco systems a voltage regulator such as shown at C, Fig. 39 (Chapter II) is used. The

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Fig. 175.—Simple Water Analogy to Outline Clearly the Operation of the

1913 and 1914 Delco Voltage Regulator.

function of this device is to prevent too much current flowing to the storage battery when the engine is running at high speed. As the voltage of the storage battery will vary with its condition of charge the intensity of the magnetic pull exerted by the solenoid A upon the plunger C varies and causes a contact attached to the plunger to move in and out of mercury which is contained in the bottom of the mercury tube B. When the battery is in a discharged condition the plunger C assumes a low position in the mercury tube, and when in this position the coil of resistance wire carried upon the lower portion is immersed in the mercury, and

as the plunger rises the coil is withdrawn. As the plunger is withdrawn from the mercury more resistance is thrown into the circuit and the greater resistance causes the amount of current flowing to the battery to be gradually reduced as the battery nears the state of complete charge until finally the plunger is almost completely withdrawn from the 'mercury, throwing the entire length of the resistance coil into the shunt field circuit, thus causing an electrical balance between the battery and the generator and eliminating any possibility of over-charging the battery. A description of the voltage regulator follows: A solenoid coil A surrounds the upper half of a mercury-containing tube B. A plunger C, comprising an iron tube with a coil of resistance wire R wrapped around the lower portion on top of mica insulation, is adapted to be drawn up into the solenoid as the battery current increases in strength. One end of this resistance coil is attached to the lower • end of the tube, the other end being connected to a rod B in the center of the plunger. The lower portion of the mercury tube is divided into two concentric wells by an insulating member, the plunger tube being partly immersed in the outer well and the rod in the inner well. The space in the mercury tube above the mercury is filled with a special oil, which serves to lubricate the plunger as well as protect the mercury from oxidation. The device is connected to the shunt field of the generator so that the current must follow a path leading into the outer well of mercury through the resistance coil R to the rods carried at the center of the plunger, from thence into the center well of mercury and out of the regulator. The more the resistance coil R is pulled out of the mercury the more resistance is interposed in the field circuit and a smaller amount of the generator current is going to charge the storage battery.

The illustration at Fig. 175 makes the operation of the 1914 Delco voltage regulator easily understood and here again we use the water analogy. When the water tank is empty little resistance is offered to the flow of water into it. This means that but small pressure is necessary to overcome the resistance and to force the water into the tank. The regulating valve will remain wide open and allow a large quantity of water to be pumped. As the amount

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