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is only intended to prevent excessive current generation. An adjustment is provided by means of a slotted segment and bolt on the fan support for varying the belt tension.
The Bosch-Rushmore System.-Bosch-Rushmore Systems are made in two forms, the chief difference being in the generator construction. One form is of the current regulation type, while the other operates on the voltage regulation principle. The complete wiring diagram given at Fig. 231 shows all connections of the Bosch Standard Lighting and Starting System. A supplementary circuit diagram is presented to show the methods of current regulation. This is accomplished by a ballast or bucking coil which interposes resistance to weaken the magnetic field and keep the generator output reasonably constant. The starting motor is of the well-known Rushmore pattern which has the automatic gear meshing feature produced by a laterally shiftable armature. The method of operation is outlined at Fig. 232. The starting motor armature is normally pushed over to one side of the motor field, the position being such that the starting pinion carried on the armature shaft is out of mesh with the large flywheel gear. A 12 volt battery is used in connection with this system. The first movement of the starting switch plunger draws the armature into the field and against the resistance of the coil spring that act to unmesh the gears. Further movement permits the starting current to flow through the starting motor windings, which of course, turns the engine over after the pinion has been positively meshed with the flywheel gear.
Some of the parts comprising the Bosch System are shown at Fig. 233. The Bosch De Luxe System, which is the electrical equipment of the Model 6-41-1915 Marmon car is shown at Fig. 234. The application of the ignition generating and starting units to the 6-41 power plant is outlined at Fig. 235. The generator and ignition magneto are placed on the same side of the motor while the starting motor is placed on the valve side and is carried by a substantial bracket in such a position that the pinion on the armature shaft will engage promptly with the starting gear cut on the flywheel. The application of the various control units of the De Luxe system on the car may be readily ascertained by inspecting the views at Fig. 236. The ignition function is normally
Fig. 233.—Parts of the Bosch-Rushmore Starting and Lighting System.
independent of the lighting and starting system as a Bosch “Vibrating Duplex'' magneto is employed. The only time the battery
is called upon to contribute to the ignition is when the engine is cranked over very slowly, when it produces a spark through the Duplex coil to facilitate starting. A special enclosed type of coil is mounted under the dash cowl, this is in series with the battery and also with the primary winding of the magneto. With this system only a single wire runs to the magneto, and no additional timing device is necessary. When the ignition switch is on battery position the coil receives current from the storage battery, this augments the natural action of the magneto and gives a hot spark even at very low speeds. The coil is connected so that it will operate over a wide range of voltage and will provide positive ignition even though the starting motor will barely turn the engine over on account of a depreciated battery.
When the starter pedal is released after the engine starts the ignition switch should be moved to the “MN” or the magneto position in order to obtain straight magneto ignition. A 12 volt starting and lighting circuit is employed, all units, including the lamps being of this voltage. The one wire system is employed, the positive battery connection being grounded through a fuse. Instead of relying upon local grounds for each connection an armored cable is used which not only serves to protect the wires but the metallic armor makes a positive return. An ingenious connection is provided for joining the various cables, so that not only a fine mechanical joint is obtained but at the same time a good electrical contact results. The generator is a simple shunt wound machine obtaining all regulations by means of external appliances. The rotating armature, which is carried on ball bearings, is provided with a fan for purposes of ventilation. An automatic reverse current relay in the switch and meter box on the dash opens the battery circuit whenever the generator is not running, thus preventing an escape of battery current through the generator.
A voltage regulator provides for the constant maintenance of the correct electro-motive force at all times. The regulator is so constructed that it will maintain a fixed voltage while carrying the entire lamp load at low motor speed and will not vary when a change is made either in speed or load. The regulation means must also take care of the internal conditions of the battery. If
Fig. 234.-Wiring Diagram Showing Relation of Parts of Bosch-Rushmore Starting and Lighting System Used on the Marmon Six-41 Automobile.
the battery is totally discharged the regulation must be such that a tapering charge is given. The amount of current flowing to the battery must become less as the charge nears completion. The regulator requires absolutely no attention as there is practically
Fig. 235.—Method of Installing Bosch-Rushmore Starting Motors on Mar
mon Engines Shown at the Top. Location of Ignition Magneto and Current Generator Depicted at the Bottom.
nothing to get out of order. The generator terminals, lamp and battery wires all lead into the switch box on the dash, which contains, besides the regulating devices, the volt-ammeter and the