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battery contact maker is incorporated as an auxiliary to the usual form of magneto contact breaker or the magneto contact breaker itself serves to interrupt the primary current from the battery as well as that from the armature winding. In the system shown at Fig. 109 the battery contact maker is carried at the lower portion of

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Fig. 109.—Wiring Diagram of Bosch Dual System Using One Set of


the magneto breaker box. The induction coil is combined with a switch and is a form that can be easily secured to the dash of the car. The greater portion of the coil box extends through the dash and the connections as they are made can be clearly followed by reference to the diagram.

Q. What is the “Unisparker” system?

A. This is a secondary distributor system in which a non-vibrator coil is employed in connection with a form of timer having platinum points that establishes instantaneous contact and sends just one impulse through the primary winding of the induction coil instead of a series of impulses as produced by the ordinary roller contact timer and vibrator. It is contended that the one impulse

will generate a strong enough spark to explode any charge of gas the cylinder may contain and that the short contact is very economical of battery energy because it does not require as long a period of discharge as do the roller contact forms of .timers, and there is a greater period of time between the battery discharges to permit the cells to recuperate, which is an important factor when primary current generators of the dry cell type are employed. This system is not as extensively used at the present time as it has been in the past owing to rapid strides made by the magneto in popular favor.

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Fig. 110.—Two-Point Ignition System for One-Cylinder Engine.
Q. What is two-point ignition?

A. Two-point ignition systems are those in which two sparks are made to occur simultaneously at separate points in the combustion chamber. A typical two-point ignition system intended for a one cylinder engine is clearly outlined at Fig 110. As will be seen one spark plug is carried over each valve of a T head engine cylinder. The coil used has two secondary terminals instead of

having one of the secondary leads grounded as is common practice. One secondary terminal goes to the insulated terminal of one spark plug while the other is joined in a similar manner to the other member. The primary winding is just the same as employed for the usual form of induction coil. Every time the contact is established at the timer and the spark coil brought into action the secondary current is forced to leap two gaps instead of one and a spark is produced at each plug at practically the same instant.

Q. What are the advantages of this method?

A. On engines of the T head form which have large combustion chambers it is claimed that the two point ignition system will result in more energetic ignition because combustion is more rapid due to the compressed charge having been fired at two different points. The advantages of this system are not apparent at low or moderate engine speeds but at high speeds Fig. 111.-Double Distributor Magneto, it is claimed that a 20%

Utilized for Two-Point Ignition System. increase of power is obtained over the single spark ignition system.

Q. What special apparatus is needed for two point ignition?

A. Either the spark coil or the spark plugs must differ from conventional construction in order to obtain two point ignition. If spark plugs of the conventional type are used as shown at Fig. 110 the induction coil must have two secondary terminals for each unit and the secondary current cannot be grounded, as is the conventional practice. If the regular form of spark coil is used having a grounded secondary terminal it is necessary to employ a special form of spark plug in connection with one of a regular pattern in each cylinder. A special two-point plug having two insulated electrodes passing through the insulating member must be used instead of the conventional pattern and this is introduced in the secondary circuit so that it is in series with the spark plug of the regular pattern used in conjunction with it. The spark must jump the gap at the two point plug before it can reach the gap between the electrodes of the regular pattern plug.


Q. Can two point ignition be obtained when magnetos are used ?

A. A special form of magneto is necessary to obtain two-point ignition and use magneto current. A device of this kind is illustrated at Fig. 111 and it differs from the conventional construction, inasmuch as it has two secondary distributors and practically two separate windings on the magneto armature if

it is a true high tenFig. 112.-Showing Utility of Insulated Ter- sion type. If used in

minal to Test Current Flow to Spark connection with a transPlugs.

former coil system a four terminal coil will be needed instead of the usual form and each of the secondary leads connected to its respective distributor. One contact breaker serves both distributors on either the true high tension or transformer coil forms.

Q. How can current flow to plugs be tested with magneto system?

A. The current delivery to the ignition plugs can be easily ascertained when a magneto is used by an insulated terminal such as

outlined at Fig. 112. When it is suspected that a plug is not firing it is possible to remove the terminal from the plug without danger of electrical shock and then by holding the terminal away from the plug electrode an eighth of an inch it is possible to see the current jump the air gap and thus determine if the electricity reaches the spark plug. If a spark jumps between the terminals and the plugs and the cylinder does not fire it is reasonable to assume that the plug is dirty and that the trouble is not with the magneto. If no spark jumps between the terminal and the plug it indicates either a broken or grounded wire or a defective contact at the distributor.

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