Third Brush
Plate Slotted To Permit
Third Brush Adjustment
Fig. 94. Delco Motor Generator—Diagram of Operation
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.
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 [Fig. 93]. This forces grease through the hollow shaft to the inside of the clutch. This cup should be given a turn or two every week.
When the cranking operation is finished the top brush is raised off the commutator when the starting pedal is released. This throws the starting motor out of action ([Fig. 94]). The top brush comes in contact with the generator commutator, and the armature is driven by the extension of the pump shaft.
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 ammeter in the charge direction to 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.