Putnam's Automobile Handbook: The Care and Management of the Modern Motor-Car

by H. Clifford Brokaw; Charles A. Starr

Attached to the motor are the carburetor, in which air and gasoline are mixed properly for rapid combustion, wires to supply ignition to the mixture at the proper time, a device for giving lubrication, and exhaust pipes leading to the muffler, the latter designed to stifle the noise of rapid explosions, which otherwise would be deafening.

The ignition system may be either battery and coil, or high-tension magneto which has its own coil and distributor, or a combination of both these systems. Where there is a self-starter there is a storage battery, which supplies current to the starting motor, and from which the ignition current is drawn, and a generator to keep the battery charged, and the generator may be provided with a circuit breaker and distributor, or a separate magneto or coil may be used.

The lubricating device may either be a gravity or force-feed oiler system with pipes leading to the various bearings, or the chief lubrication may be by the splash system, where a reservoir of oil is kept under the crank case from which it is pumped to oil pans under the cranks, being splashed by projections which dip into the oil and throw it all over the inside mechanism.

Also attached to the carburetor is the pipe from the fuel supply tank. This supply may come by gravity or under pressure, and a late device which is furnished with many cars is a vacuum gravity system, the gasoline being drawn from the main tank, by a vacuum created in the intake manifold, into a small container attached under the hood, whence it flows by gravity to the carburetor, maintaining a uniform supply.

The motor consists of one or more cylinders, inside of each being a piston which fits tight, the escape of gas being further prevented by piston rings which seal the cylinder with the aid of the lubricating oil. The pistons are attached to a connecting rod by a wrist pin, the connecting rod being attached at the other end to the crank which rests in bearings. The action of the engine is that by drawing down the piston a vacuum is created in the upper part of the cylinder called the combustion chamber. At the right moment an inlet valve is opened and a charge of gas and air, called mixture, is sucked in. The valve closes and the piston rising compresses the charge. When the piston reaches its highest point a spark is introduced through spark plug or igniter. This fires the mixture, bringing a rapid expansion, and this drives the piston downward, producing force. This revolves the crank shaft, which turns the force into rotary motion. This operation repeated rapidly furnishes the motion which drives the car. The fly wheel carries the crank over the strokes which do not produce power.

There are four strokes to each motor cycle. The first, which takes in the mixture, is called the suction stroke; the next is the compression stroke, the third is the power stroke, and the last is the exhaust stroke when the burned gases are expelled from the combustion chamber. These four strokes take two complete revolutions of the crank shaft, so that the four cycle is really two circles.

Power having been created and turned into motion, the next step is to connect it to the propelling or drive wheels. The first device for controlling the power is the clutch, which provides means of applying or cutting off the power or motion quickly without stopping the engine. This is done by friction in some form. The most common are the cone clutch, where male and female cones are engaged by pressure, the friction transmitting the power to the driving shaft; and the multiple disc clutch, where numerous thin discs of metal or metal and textile material are compressed together by a lever and transmit the power.

To provide for varying speeds and for reversing, also extra power to the rear wheels for hill climbing, sandy roads, etc., gears are necessary. In a general way this is a set of cog wheels of varying sizes, so arranged on parallel shafts that by engaging different size gears on the shafts a certain speed will be transmitted, other gear sets producing another speed or a reverse motion. The diagram in Chapter XXI. shows the usual form of construction. Three speeds and reverse usually are provided, though some cars have four speeds. These gear sets are engaged successively until the desired speed is reached.

From the gear case the power is transmitted by the drive shaft, which has one or two universal joints to take up any misalignment and to enable installing the engine level and yet transmit the power to the driving axles, through the differential, at another level or angle, or at varying angles due to spring action.

Upon each of the wheels is a tire consisting of a rubber and fabric casing, enclosing a soft rubber tube with a valve by which it may be inflated. The purpose of the tires is to absorb road shocks and make riding easy, as well as to keep the car from jolting to pieces. The tires are of varying composition and form and are attached to the rims in differing ways. Many auto trucks use solid rubber tires.