Le screw.

secording to the number of cylinders to be fired, cut into it. A light, hardened steel trigger is held against the shaft at this point by a small spring. On turning the shaft this trigger is carried forward by the notches in the shaft, and is suddenly released as the book end leaves the notch. In so doing the back of the trigger strikes a small pivoted hammer situated between the trigger and the spring carrying the contact points. This causes the contact points to open and close with remarkable rapidity, but one contact eing made for each spark. When it is desired to adjust the platum contact points, as when they show signs of wear, it is only Decessary to remove one or more of a number of extremely thin Fashers under the head of the adjustment screw and to replace The contact points should be absolutely clean and right and have smooth contacting surfaces. The distributor portion of the device consists of a hard rubber block fitted to the p of the primary shaft, this carrying a brass quadrant that passes the high tension current to the spark plugs by means of the terminal points imbedded in the hemispherical cover. There is no actual contact between the rotating quadrant and the distributor points, as the high tension current is capable of jumping the very light gap that exists between them. Owing to there being no actal contact, there will be no depreciation in the distributor or pper portion. The center terminal, which is in connection with the induction coil, is a combination of carbon and brass, and a ght, flat spring on the quadrant bears against it to maintain Positive electrical connection. The distributor cover is easily reLoved without the use of tools, as it is held by spring clips. Location or dowel pins in its lower edge insure that it will be replaced in the correct position.

One of the most popular of the combined starting, lighting and ignition systems is the Delco, which is shown at Fig. 236. For the present we will concern ourselves merely with discussing the ignition functions of the system, leaving the self-starting and ectric lighting features for more comprehensive consideration in the following chapter. Current is produced by a one unit type motor-generator, although the windings of the device when operated as a motor or a generator are entirely separate. The ignition

current is obtained either from a storage battery which is kept in a state of charge by the generator, or from a set of dry cells which are carried for reserve ignition. The ignition system consists of a one unit non-vibrator coil, sometimes attached to the top of the motor generator, as shown at Fig. 236, though it may be placed at any convenient part of the car and a dual automatic distributor and timer usually included as a part of the device as shown. When ignition current is supplied from the lighting circuit the current passes from the storage battery through a switch and out to the low tension winding of the coil, from whence it passes to the timer and from there to the frame, where it is grounded. The high tension current generated in the coil runs to the distributor, where it is switched to the spark plug in the different cylinders in turn.

When dry cells are used for ignition the operation is the same except that a device called "the ignition relay," and shown at the right of Fig. 238, is added to the circuit. The function of this device is to break the circuit immediately after it has been completed by the contact points of the timer, which is shown at the left. The use of the ignition relay results in a material saving of the battery current as the circuit is closed a much shorter time than is the case when the circuit is broken by the timer contacts themselves. The operation of the relay is not difficult to understand. The magnet A attracts the armature B when the circuit is completed through the timer. This action opens contact C and breaks the timer circuit. A condenser D is mounted besides the magnet coil A, in order to absorb the current produced by selfinduction in the magnet winding, which would be apt to produce a hot spark between the contact points when they were separated if no means were taken for its disposal. The adjustment of the relay is at the pole piece E. This regulates the distance between the armature B and the magnet pole, and the gap between the contacts C. The adjustment is made by turning the notched head at E clockwise to increase, anti-clockwise to decrease, the gap between the contacts. The correct distance between contacts C when the armature B is pressed down is equal to approximately the thickness of one sheet of newspaper. A very simple way in which

the adjustment can be made when the engine is running on the battery is to turn the notched head of the pole piece in the counter clockwise direction until the motor ceases to fire. Then turn i four or five notches in the opposite direction. Under no condi tions should the adjustment screw be turned very far in either direction. If the armature vibrates feebly when the starting but

ton is pressed it indicates either weak dry cells or dirt betwee the relay or timer contacts.

The interior arrangement of a timer for both dry cells am storage battery current is shown at Fig. 238. The cam Ci driven by a rotating shaft and establishes contact between th points when the cam rider rises on the point of the cam. Whe the cam rider drops into the notch between the high points th contact points separate. The same instructions that have bee given for the contact points of the Atwater-Kent timer apply jus as well in this case. While the contact points are but one-eight inch in diameter, it is said that many thousands of miles of servic may be obtained without readjusting. It is important that th

contact spring, which is the straight one carrying the platinum point, should have a good tension outward against the cam rider member below it. It is said that this spring should be capable of supporting the weight of half a pound. If the tension is not sufficiently great the contact points barely break contact which permits the spark to arc between them, tending to burn them.

System.

The contact should be so adjusted that the contact spring is forced away from the breaker member at least half the distance of the T-slot on the vertical part of the cam rider, when the latter is on the contact lobe of the cam. The contact points should open about ten one-thousandths (.010 inch) inch when the contact arm rests upon the back stop. The contact arm should clear the cam except at the contact lobe. A short wire connects the two posts of the breaker arms and this connection should always be inspected when making adjustments to insure that it has not been disturbed. It is said that if this wire is disconnected the current will pass