Kinds of Ignition Schemes.-There are two kinds of ignition schemes used on gas engines to fire the fuel charge and these are (1) the hot tube igniter and (2) electric ignition systems.

The Hot Tube Igniter.-This is a simple, but it is not a very safe, ignition scheme. It consists of a steel tube open at one end and closed at the other;

WIPER OIL CUP

CONNECTING
ROD

WIPE NITER

SPARK

CAM OR

GEAR SHAFT

FRAME

SPIRAL OR WORM GEARS

the

open end is fixed in the cylinder near the head so that the fuel charge can reach it, and it is kept white hot by the flame of a Bunsen burner.

The walls of the tube are about inch thick, it has an outside diameter of about 1/2 an inch, and a length of about 5 inches. An iron tube 11/2 inches in diameter and lined with asbestos sets around the hot tube to prevent the loss of heat; a lot of little

air holes are drilled near the lower end of the iron tube and just above them a 12-inch pipe is screwed into it. This pipe is connected to a gas supply and this provides the flame to heat the tube. The whole scheme is shown in cross-section in Fig. 23.

The way the hot-tube works is like this: the instant the fuel mixture is compressed either an igni

FIG. 22. HOW THE GAS IS SUPPLIED TO THE ENGINE

tion valve is opened by a cam on the camshaft or the piston slides off of a port or hole which opens into the tube. The fuel charge then rushes into the incandescent tube when it is ignited, and the flame sweeps back into the cylinder and fires the charge. This hot tube igniter is a very decided improvement over Barnett's ignition cock, which I described in the first chapter.

Kinds of Electric Igniters.-There are two kinds of electric ignition systems used on gas engines, and these are (1) the wipe spark, or make and break system and (2) the jump-spark system.

Wipe Spark Igniters.-The Battery and Spark Coil System.-Likewise, there are two kinds of wipe spark igniters and these are (1) the battery and spark coil system and (2) the magneto system. ASBESTOS

FIG. 23. THE CONSTRUCTION OF A HOT TUBE IGNITER

Where a battery and spark coil is used the system is formed of four chief parts, namely, (1) the battery, (2) the spark-coil, (3) the igniter mechanism, and (4) the wipe spark electrodes.

The battery consists of half a dozen dry, EdisonLalande or storage cells. The spark-coil, or kick-coil as it is called, is the kind used for lighting gas jets, that is, it is made up of a single coil of No. 16 or 18 insulated copper wire wound on a soft iron core.

The purpose of this coil is to raise the voltage, that is, the pressure of the battery current, so that when the circuit is broken it will give a good hot spark. This the coil does by the action of the current on itself as it flows through the adjacent turns of wire, and the higher tension current thus set up is called the extra current.

The wipe spark electrodes consist of a fixed contact point and a movable contact point, both of which

FIG. 24. THE WIPE SPARK IGNITER OPERATED BY A BATTERY AND A KICK COIL

are mounted on a flange; this is bolted to the head of the cylinder so that the electrodes are inside of the latter and the binding posts of the electrodes and the lever which works the movable electrode are outside of the cylinder head. The fixed and movable electrodes are well insulated from each other so that the current will not short circuit. The scheme is shown in Fig. 24.

The igniter mechanism is simply a lever worked

by the camshaft which presses against the interruptor lever with the movable electrode on it until the latter makes contact with the fixed electrode and the circuit is then closed.

At the right instant the pressure on the movable electrode lever is released and a spring makes it snap back, thus wiping the fixed electrode and break

NDVABLOD

NTERRUPTOR
LEVER

FIG. 25. THE MECHANISM OF THE WIPE SPARK IGNITER

A, Cross Section of the Wipe Spark Igniter. B, The Igniter Ready to Use.

ing the contact between them, and this makes a spark. An Otto igniter is shown at A and B in Fig. 25, and the mechanism working it is shown at A and B in Fig. 26.

Low Tension Magneto System.-A magneto electric machine, or just magneto for short, is a machine which generates electric alternating currents. There are two kinds of low tension magnetos made,