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 counterclockwise direction until the motor ceases to fire. Then turn it four or five notches in the opposite direction. Under no conditions should the adjustment screw be turned very far in either direction. If the armature vibrates feebly when the starting button is pressed it indicates either weak dry cells or dirt between the relay or timer contacts.

The interior arrangement of one form of timer for both dry cells and storage battery current is shown at Fig. 38. The cam C is driven by a rotating shaft and establishes contact between the points when the cam rider rises on the point of the cam. When the cam rider drops into the notch between the high points the contact points separate. The same instructions that have been given for the contact points of the Atwater-Kent timer apply just as well in this case. While the contact points are but one-eighth inch in diameter, it is said that many thousands of miles of service may be obtained without readjusting. It is important that the 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 are between them, tending to burn them. 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 through the contact spring, impairing its tension. Whenever the contact points are cleaned care should be taken to have the surfaces parallel.

In some of the Delco ignition systems an automatic spark advance mechanism is used. The usual method of wiring when the distributor is a separate member from the generator is shown at A, the left of Fig. 39. The construction of, the automatic spark advance mechanism is shown at B. In this the shaft which trans

mits motion to the timer is in the form of a tube T, revolved by spiral gears. An inclined slot is cut through the walls of this hollow driving member. A smaller shaft is carried inside of the hollow member, and a vertical slot is cut through this shaft in order to permit a pin to pass through it, said pin being actuated by a collar adapted to slide up and down on the outside of the hollow driving shaft. The pin passes through both the straight

Fig. 39.-Parts of Delco 1914 System. A-Delco Timer, Coil and Condenser Assembly. B-Construction of Delco Automatic Spark Advance. C-Delco Voltage Regulator.

slot in the small shaft and the incline slot in the hollow driving member. If the collar holding the pin is moved it will change its angular relation with the small shaft which will advance the timing cam of the contact breaker. The collar is shifted by a spring loaded revolving ring R, which moves from the position shown in the drawing to a horizontal position as the speed increases. This ring is connected to the sliding collar and causes it to rise, advancing the spark as the engine speeds up or to fall, retarding the spark as the engine speed decreases. If desired, the spark

timing may be controlled independently of the automatic advance mechanism by a spark lever connected to the corresponding member on the steering wheel. The voltage regulator, which will be described when discussing the generating function of the Delco instrument, is shown at Fig. 39, C.

Condenser. The condenser consists of two long strips of folded tinfoil insulated from each other by paraffined or oiled paper, and connected as shown in Fig. 40. The condenser has the property of being able to hold a certain quantity of electrical energy, and like the storage battery, will discharge this energy if there is any circuit between its terminal. As the distributor contacts open the magnetism commences to die out of the iron core, this induces a voltage in both the primary and secondary windings of the coil. This induced voltage in the primary winding amounts to from 100 to 125 volts. This charges the condenser which immediately discharges itself through the primary winding of the coil in the reverse direction from which the ignition current originally flows. This discharge of the condenser causes the iron core of the coil to be quickly demagnetized and remagnetized in the reverse direction, with the result that the change of magnetism within the secondary winding is very rapid, thus producing a high voltage in the secondary winding which is necessary for ignition purposes. In addition to rapidly demagnetizing the coil the condenser prevents sparking at the breaker contacts-thus it is evident that the action of the condenser can very seriously affect the amount of the spark from the secondary winding and the amount of sparking obtained at the timer contacts.

Ignition Coil. This is sometimes mounted on top of the motor generator and is what is generally known as the ignition transformer coil. In addition to being a plain transformer coil it has incorporated in it a condenser (which is necessary for all high tension ignition systems) and has included on the rear end an ignition resistance unit. The coil proper consists of a round core of a number of small iron wires. Wound around this and insulated from it is the primary winding. The circuit and arrangement of the different parts are shown in Fig. 41. The primary current is supplied through the combination switch and resistance on the