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them at once, using terminals for all wires as shown at Fig. 89, making sure no loose strands of wire project. Terminals should be securely soldered to wire.

Be sure all timer contacts are clean, contact points properly adjusted and distributor brushes 0. K. Carbon dust in distributor will cause skipping as well oil in timer portion on points.

Don't think the ignition system will function properly with loose or dirty switch connections. Examine switch parts as shown at Fig. 90 for looseness or corrosion of contacts.

Timing Battery Ignition Systems.—In timing'a motor using a battery ignition system with individual vibrator coils to supply the current to respective cylinders, the first thing to ascertain is the firing order of the engine to be timed. The diagram, Fig. 91, shows all components of a battery ignition system, also a sectional view of one of the cylinders of the engine, showing the position of the piston when the spark should occur in the cylinder with the primary timer fully advanced. When the primary timer is fully retarded the spark will take place after the piston has reached the top of its stroke and has started to go down on the explosion stroke. The four unit spark coil has a two point switch on its face and has ten terminals. Four of these which are protected by heavy insulators or bushings of hard rubber run to the spark plugs as indicated. These are the secondary terminals. The two primary terminals under the switch are connected to the positive poles of the dry cell and storage batteries respectively, the negative terminals of the two batteries being joined together by a common wire and grounded. This leaves four primary leads which go to insulated terminals connecting with the segments of the timer.

The method of timing an engine is very simple. The spark advance lever on the steering wheel is advanced fully. The inlet valve of cylinder No. 1 is watched as the engine is turned by the hand crank. Just after the inlet valve closes which indicates that the piston has started to go up on its compression stroke the piston travel may be gauged accurately as it moves up by the timing rod inserted through a petcock in the top of the cylinder or through a valve cap opening. If the engine is not provided with a relief

cock or spark plug that will permit the use of the gauge rod, the flywheel markings may be utilized to determine the center corresponding to the end of the piston upward movement. The vibrator of coil connected to cylinder No. 1 should begin to buzz with the

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Fig. 91.—Simplified Wiring Diagram Explaining Methods of Timing

Spark in Battery Ignition Systems.

timer casing in full advanced position before the piston reaches the end of its upward stroke. The amount of crankshaft travel is about 30 degrees from the point where the spark takes place to that where the piston reaches the top of its stroke. If the timer casing is set in full retard position the spark should take place 30 degrees of the crankshaft travel after the piston has left the

end of its compression stroke. Some engines have the spark set 45 degrees advance. With the spark advance lever set about half way of its travel the spark may be made to occur just when the piston reaches the end of its compression stroke, or on top center. It is necessary to provide a wider range of spark advance on a battery and coil ignition system than when a magneto is used, as it is said that a range of advance of 60 degrees is sufficient for four-cylinder motors and 27 degrees for six-cylinder motors with magneto ignition.

In timing a strange car it is easy to tell whether the movement of the spark lever advances or retards the timer case by noting the direction of movement of that member. If the spark advance lever is pushed in a certain direction, say from the point on the sector nearest the driver to the other extreme, and the segments on the timer move to meet the advancing contact roller, it is evident that a movement of the spark advance lever from front to rear advances the ignition. If the timer case oscillates so the segment moves away from the advancing contact roller, that movement of the spark lever retards the ignition. In most timers the rotating contact member is fastened to the shaft in such a way that it may be moved independent of engine rotation, if desired, by releasing the fastening. Sometimes it is held on a tapered shaft by a clamping nut, in other constructions it is driven by a hollow shaft which is set screwed to the timer driving shaft the position of which can be changed as desired. In every case the roller should be set in contact with the segments joined to coil unit No. 1, the remaining terminals being wired according to the firing order and the direction of rotation of the timer brush. In the diagram now under discussion after the roller leaves unit No. 1 segment it will go to that in connection with unit No. 2, then to the one joined to unit No. 4, and finally to the terminal conveying the electrical current to unit No. 3. This means that the plug in cylinder No. 1 fires first, followed by those in cylinders 2, 4, 3, in the order named. With the switch lever in the position shown or between the two contact buttons, the ignition is interrupted and battery current cannot flow to the coil unit. If the switch lever is moved to the button on the right marked “storage battery,” the secondary current producer will furnish ignition. If moved to the button on the left, the dry cells will be brought into action. The same method is employed in timing a two, three or six-cylinder motor, the only precaution to be observed being to run the wires from the timer to the coils so the cylinders will fire in proper order.

At one time secondary distributor systems using a single unit vibrator coil for firing a multiple cylinder engine were very popular, but at the present time few cars use the long contact timer and distributor combination. The modern cars that employ battery ignition use a short contact timer and a non-vibrator coil unit. Popular systems of this nature are the Atwater-Kent and the Delco, both of which have been previously described. Practically the same method of timing is employed with these systems except that there is but one primary terminal on the contact breaker portion of the distributor which is joined to the corresponding terminal of the spark coil. A proper distribution of current to the cylinders is made by connecting the distributing terminals to the plugs in proper firing order.

CHAPTER III
MAGNETO IGNITION SYSTEMS

Magneto Generator Construction—Low Tension Magnetos—Typical American

Magneto Forms—Magnetos for Eight- and Twelve-Cylinder MotorsSimple Magneto Ignition System Double System—Transformer Coil Method—Dual Ignition-Duplex Ignition—Two-Spark Magneto—Magnetic Plug System-Impulse Starter-Automatic Spark Advance—Low Tension Magneto Troubles—High Tension Magneto Troubles—Recharging Magnets

-Adjusting Parts—Application to Typical Engines—Timing Magneto Ignition System-Firing Orders of Typical Engines.

Magneto Generator Construction. The magneto is a simple form of dynamo and a mechanical generator of electricity in which permanent magnets are used to produce the magnetic field and between which the armature revolves. The permanent magnets are called “field magnets" and at their ends are provided cast-iron shoes which form the walls of the armature tunnel and which are known as pole pieces. A typical magneto adapted for single-cylinder ignition is shown in section at Fig. 92. It consists of two compound horseshoe magnets attached to the pole pieces which collect and concentrate the magnetism upon the armature. The armature is shuttle-shaped and carries a double winding of wire which consists of two coils, one of coarse, the other of fine conductor. The armature is attached to end pieces which carry shafts and the whole assembly revolves on annular ball bearings. An ebonite or hard rubber spool is carried at one end while the condenser is housed at the other. The make-and-break mechanism is partly carried by an oscillating casing and the revolving member is turned from the armature shaft.

The current generated in the coil is delivered to a metal ring on the ebonite spool from which it is taken by a carbon brush and delivered directly to the spark plug. Every time the contact points

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