These segments are held in position by screw bolts which pass through the fiber ring and housing, hut are insulated from the latter. These screw bolts are provided with thumb nuts and terminals to which is secured a primary wire, which in turn is connected to the primary terminal of the induction coil.

Transformer Coll.

Fig. 53. Transformer Coll.

Wiring Diagram of an Induction Coil and the Other Components of a Battery System.

Fig. 54. Wiring Diagram of an Induction Coil and the Other Components of a Battery System.

Timer for Battery System.

Fig. 55. Timer for Battery System.

The operation of the timer is as follows: The shaft actuating the roller is metal, and one lead from the battery is connected to the frame, or other metal part, and the current is conducted from its source to the metal segment. As the roller makes contact with the segment in the fiber ring, the circuit is closed and the current flows through the roller frame and primary wire back to its original source. As the roller contact with the segment is broken, the primary current in the coil is established and broken as previously described, being built up in the secondary winding, and a spark produced at the gap of the spark plug electrodes.

The vibrator coil system has its disadvantages, having several primary contacts, sliding or rolling contacts in the timer, and a delicate, magnetic interrupter. To overcome these faults, igniters were introduced which combine a mechanical interrupter with a high-tension distributor. The induction coil is replaced by a transformer coil, as used with the primary armature type of magneto. With the igniter system but one primary contact is necessary and the circuit is made and broken positively by mechanical means.

The contact points are generally so constructed that they may be adjusted from the outside without dismantling the unit.

Directly above the contact maker is located the high-tension distributor. Its construction is similar to the high-tension magneto distributor, using a central contact brush and segments located radially which are connected with the spark plugs of the motor.

The advantages of this system over the vibrator coil system are two-fold. As there is only one set of wearing parts, whatever wear occurs will affect the timing of all cylinders equally and subsequently a perfect relationship is maintained at all times. Again the character of the spark in all cylinders must be identical.

Fig. 56 indicates the path of the current in the igniter system, passing from the battery to the switch on the coil, thence to the interrupter, from where it is led to the coil and stepped-up to a high pressure. From the coil it passes through a conductor to the central contact of the distributor and is distributed to the cylinders in proper sequence.

Either the vibrator and tinier system, or the igniter system, may be used in connection with either the primary or compound armature magneto, thus forming two separate systems of ignition, with either one or two sets of spark plugs. With the former type the magneto distributor is used for both systems, while a vibrator and a transformer coil are mounted together and controlled by a single switch. When the compound armature magneto is used, but one coil is necessary for the battery system. The above is also true of the igniter and transformed coil, excepting, of course, that but one coil is necessary for either type of magneto.

Indicating the Path of Current in an Igniter System.

Fig. 56. Indicating the Path of Current in an Igniter System.