Hand and Electric Starters.-Motor car engines are started either (1) by hand or (2) by an electric motor.

Hand Starters.-A few small new cars and a lot of the old-timers have engines with ratchet handles to crank them, and these are thrown out of gear the instant the engines start.

The Electric Starter.-Every up-to-date engine is FIELD MAGNET STARTING

MOTOR

SWITCH

STORAGE
BATTERY

ARMATURE

FIG. 53-A. WIRING DIAGRAM FOR AN ELECTRIC STARTER

equipped with an electric starter, and this is formed of four pieces of apparatus, namely, (1) a storage battery, (2) an electric motor, (3) a motor drive, and (4) a starting switch, and these are connected up, as shown at A in Fig. 53.

The storage battery is formed of prepared lead plates, or girds, immersed in a weak solution of sulphuric acid, as shown at B. Three, six, or twelve cells of storage battery are generally used, and these

must be charged with a current generated by a dynamo.

Now a dynamo and a motor are made exactly alike,

FIG. 53-C. THE ELECTRIC ENGINE DRIVE

and if you rotate the armature the machine will generate a current, and then it is called a dynamo; on the other hand if you pass a current through the

machine it will rotate the armature and then it will be a motor.

The motor drive is the mechanical part of the starter; it is formed of a screw gear mounted on the projecting shaft of the electric motor; it meshes with teeth that are cut on the rim of the flywheel of the engine, as shown at C, and demeshes from it after the engine is started. It is shown complete at D.

FIG. 53-D. THE ELECTRIC STARTER COMPLETE

The switch is a simple device for opening and closing the circuit. Now when you throw on the switch the storage battery energizes the motor and this screws the drive gear into the flywheel and turns it; as soon as the engine has started, the motor drive demeshes automatically; you release the switch and the electric motor stops. When the engine is running the motor can then be driven by it, and it will then generate current and charge the storage battery.

The Knight Sleeve Engine.-To get rid of the noise that the poppet valves make, Knight invented

an engine in which the inlet and exhaust ports are opened and closed by a sleeve that slides between the cylinder and the piston. It is shown in Fig. 54.

PART III

THE MOTOR BOAT GASOLINE ENGINE

Gasoline engines for motor boats are of the two and four cycle types and are made with one, two, four, six and eight cylinders.

The Fuel Feed System Again.-The gravity feed, the air pressure feed, and the vacuum feed systems of fuel supply are all used on motor boat engines, and these are identical with those used on motor car engines.

In small boats, the gasoline tank is often made to fit in the bow of the boat, and as this is higher than the carburetor the gasoline flows down by gravity. Where a larger supply of fuel is wanted a cylindrical pressed steel tank can be mounted on the boat back of the seat just as it is on a runabout car.

The regular float valve carburetor is used on motor boat engines, and the speed of the engine is controlled by a throttle, that is, by a lever which opens and closes the throttle valve. On large engines the flyball type of governor is used, and by means of it any speed desired can be kept up.

Electric Ignition Systems.-There are three kinds