GASOLINE AUTOMOBILES.
By WILLIAM BAXTER, Jr.
To understand the operation of a gasoline vehicle it is necessary to be somewhat familiar with the principle on which gasoline motors act. Briefly stated, it is as follows: The gasoline is converted into a vapor, and in this state is mixed with a sufficient amount of air to cause it to ignite when heated to a proper temperature. This mixture of air and vapor is admitted into a cylinder in which a piston moves freely, this part being substantially the same as in a steam engine. By means of an electric spark or a hot tube, the mixture is ignited, burning so violently as to expand the products of the combustion with such rapidity as virtually to become an explosion. The force of this explosion pushes the piston to the further end of the cylinder, and by means of a connecting rod and a crank this movement imparts a rotary motion to a shaft.
Fig. 1. Gasoline Motor.
The entire operation is made perfectly clear by the aid of [Fig. 1], which is a simple diagram of a single cylinder motor. The chamber R contains the gasoline. Air enters this chamber through tube b, as indicated by the arrow, and passes out between the plate c and the surface of the gasoline. The float d keeps the plate c in the proper position regardless of the amount of liquid in the reservoir. The heated gases exhausted from the cylinder pass through the pipe r, and thus heat the gasoline so that it vaporizes freely and the air passing under c becomes charged with the necessary proportion of vapor. The mixed air and vapor enter a valve chamber S, from which the flow into pipe e is regulated by the movement of handle a. In this chamber there is another valve, operated by an independent handle, and by means of this more air can be admitted into the mixture when desired. Through the pipe e and the valve f the vapor enters chamber Q, which connects with the top of the cylinder. Suppose the shaft G is rotating, then the piston will be drawn down from the position in which it is shown and thus a vacuum will tend to form in chamber Q. This action will cause the valve f to open and the mixture of air and vapor will flow into Q until the piston reaches its lowest position and begins to ascend. At this instant the valve f will close, and then the upward movement of the piston will compress the mixture in the chamber Q. When the piston reaches the upper position, after completing the down and up strokes, the lever l and the contact point p will come together, and an electric current developed in the induction coil M will pass through the wires j and k and produce a spark at i between the ends of the metallic terminals passing through the plug of insulating material, which is shown in dark shading. This spark will cause the mixed air and vapor to ignite, producing an explosion that will force the piston down for the second time. On the second upward movement of the piston the gases produced by the combustion of the vapor will be forced out through the valve h into the chamber T and the pipe r. The valve h and the lever l are operated by cams mounted on the shaft m, and they are so set that the spark at i occurs when the chamber Q is full of the explosive mixture and the piston is at the top of the cylinder. The valve opens when the piston begins to move upward after the explosion has forced it to the bottom position.
As will be seen, the piston must move down to draw in a supply of the explosive mixture; it then moves upward to compress it, and on the second down stroke it is pushed by the force of the explosion. From this action it can be clearly realized that the power developed by the motor comes from the force exerted by explosions at every alternate revolution of the shaft. On that account the cams that move the valve h and the lever l are placed on a separate shaft, which is geared to the main shaft in the ratio of two to one; that is, the wheel K is twice the diameter of the wheel J. As the force of the piston acts on the shaft only once in every two revolutions it is necessary to provide a heavy fly wheel O, which will store up enough momentum to continue the rotation of the motor through the ineffective revolution. Before the motor can put forth an effort it is necessary for the piston to move downward so as to draw in a supply of explosive gases and then to move up so as to compress them and produce an explosion; therefore, the motor will not start of its own accord, but must be set in motion. In the act of starting the wheel O is turned by hand.
The combustion of the gasoline vapor within the chamber Q and the upper end of the cylinder develops a large amount of heat, and unless means are provided for dissipating it the temperature will soon rise to a point that will interfere with the proper action of the motor. Two ways are employed to carry off the heat. One is by surrounding the cylinder with a water jacket, as shown in the diagram at NN; and the other is to provide the exterior of the cylinder with numerous thin ribs so as to increase the surface exposed to the air and thus increase the radiation.
Fig. 2. Petroleum Spirit Motor.