tion coil and construction of distributor for six-cylinder engine ignition are depicted at Fig. 64. The Remy ignition system is sometimes incorporated in a combined ignition-generator, as shown in wiring diagram at Fig. 65.

Features of Low-Tension Ignition System.-Though the lowtension ignition system is seldom used at the present time, a brief description of the method of producing a make-and-break spark is desirable so the reader may gain a thorough knowledge of the

Fig. 64.-External View of Remy Induction Coil at Left and Parts of Timer-Distributor at Right.

methods of ignition in vogue. In order to obtain a spark in the cylinder of any engine, it is necessary that there be a break in the circuit and that this break or interruption be inside of the combustion chamber. The igniter plate used is different in construction from the spark plug forming part of the high-tension system, as the break is made by moving contacts which serve to time the spark as well as produce it.

A typical igniter is shown at A and B, Fig. 66. It consists of

a drop-forged plate approximately triangular in form which has a conical ground surface to fit a corresponding female member in the combustion chamber. It is secured by three bolts to a corner of the cylinder close to the inlet valve so the contact points will be traversed by the gases entering from the carburetor. As shown at B, the fixed contact point is called the anvil, while the movable

or rocking member is called the hammer. The anvil is insulated from the igniter plate by a bushing of mica or lava, and the hammer alternately makes and breaks contact with the anvil. The method of actuating the hammer by a rocker arm is clearly shown at Fig. 67, B. The rocker arm H is in the form of a short lever ending in a slotted opening which is connected to the top of the vertical lifter rod T. This is actuated by a cam on the inlet valve cam shaft C, which raises the plunger in the guide

bushing. When the lifter rod moves upward the contact point on the hammer inside of the cylinder comes into contact with the platinum point on the anvil and closes the circuit. When the igniter cam reaches the proper point for igniting the charge the lifter rod T falls and as the action is quickened by a spring, S, 1,

at the bottom of the lifter rod the hammer arm is separated from the contact point on the anvil and a spark takes place as the points are pulled apart.

The coil used when batteries are employed to furnish the current is a simple form. It is a winding of comparatively coarse wire around a core composed of a bundle of soft iron wire. The battery current is intensified to a certain extent by the self-induction of one layer of wire upon the others, and when contact is broka brilliant spark occurs between the

points of the igniter plate. Batteries are seldom used for regular service on the low-tension system because the demands are too severe.

One of the advantages of this system is that the wiring is extremely simple, as will be seen by consulting the diagram of the low-tension ignition system illustrated at Fig. 67, A. In this both a low-tension magneto and set of batteries are provided, the former

being used for regular ignition while the latter are carried for emergency service. A simple form of magneto will serve any number of cylinders because the insulated terminals of the igniters are joined together by a simple conductor or bus bar. A wire from the magneto terminal is joined to one side of the switch, while the other side of the switch is coupled to the coil which is carried in

Fig. 67.—Diagram Showing Method of Operating Locomobile Low Tension

Igniter.

the battery box. A short wire connects the top of the switch lever with the bus bar. If the switch lever is swung to the left, the magneto produces the current for the igniters, and if the switch lever is placed on the button at the right, the current, supply is taken from the batteries. The dry cells are joined together in series connection, one pole being joined to a coil terminal, the other being grounded. The coil and the igniter plates are in series with the batteries and the current is returned to the

ground through the rocker arm, which is a metallic contact with the igniter plate.

The disadvantage which has militated against the general use of the make-and-break system of ignition is that it is very difficult to obtain synchronized spark after the mechanism has become worn, and unless the igniter plates are kept in perfect adjustment the spark time will vary and the efficiency of the engine will be lowered. As the moving electrodes operate under extremely disadvantageous conditions it is difficult to prevent rapid wear of the rocker arm bearing at the igniter plate and consequent leakage of gas results. Owing to the multiplicity of joints in the operating mechanism it is difficult to secure regular action without backlash or lost motion.

With a high-tension system there are no moving parts inside of the cylinder and it is not difficult to maintain a tight joint between the plug body and the cylinder head. The timer mechanism which is employed when batteries and coils are utilized to furnish the current is a comparatively simple device which is not liable to wear because it can be easily oiled and has a regular rotating movement which can operate without getting out of time much better than the reciprocating parts of the make-and-break mechanism. When a direct high-tension magneto is used the system is not much more complicated as far as wiring is concerned than a low-tension group, and as the ignition is more reliable it is not strange that jump spark or high-tension ignition is almost generally used in automobile practice.

Double and Triple Ignition Methods. There are many cars in operation to-day which utilize double and triple ignition systems. On some of these it is possible to have three practically independent means of supplying the ignition spark. As will be apparent, the wiring of a triple ignition system is apt to be much more complex than that of the simpler methods now in vogue. In the ignition system outlined at Fig. 68, which has been used on a six cylinder car, it will be evident that in addition to the usual Bosch D-6 dual magneto an entirely independent individual spark coil and battery timer system is included. Two sets of plugs are used, one serving both magneto distributor systems, while the other