10. The BASE or FRAME of the engine acts as a foundation for the various working parts, holding them in their proper positions.
(42) Application of the Four Stroke Principle.
While the five events of every commercial four stroke cycle engine are accomplished in exactly the same order, or routine as explained in paragraph (8), Chapter 3, the actual design and method of applying the cycle varies greatly in different makes of engines. This great difference in the details of construction often makes it difficult for the novice to identify the cycle of operations in that particular engine. The different forms of valve gears that are used to perform the same functions in the cycle are good examples of the variation in design, some makers using the poppet or disc type, some the sliding sleeve, and others the rotary type.
Fig. 16. Ball Bearing Crank Shaft, Pistons and Connecting Rods of the “Maximotor,” in Their Relative Positions.
Multiple cylinder engines vary in the cylinder grouping or arrangement, the arrangement and number of cylinders depending on the service for which the engine is intended, the amount of vibration permissible, or the weight. The question of speed also introduces modifications in the design, but no matter what valve arrangement is adopted or what grouping of cylinders is used, a four stroke cycle engine performs the five events of suction, compression, ignition, expansion and exhaust in four strokes, in each and every cylinder. With the exception of fuel injection (which in reality corresponds to the ignition event) in the four stroke Diesel engine, the indicator cards of all four stroke cycle engines passes the same characteristics as the diagram shown in Fig. 10.
In this chapter, the engine will be described without regard to the fuel used, or to the means adopted in vaporizing it, for the vaporizing appliances are considered as being external to the engine proper, except in some of the heavy oil engines, and as the fuel is gasified before entering the cylinder the question of fuel does not affect the general construction of the engine. The majority of engines are readily converted from gasoline to gars, or in some cases kerosene, by changes in the vaporizing device, and with the exception of changing the compression pressure, little further alteration is needed. Since the vaporization and admission of the heavier oils, such as crude oil and kerosene has a more intimate relation to the engine than the use of gasoline or gas, the heavy oil engines will be described in a separate chapter in order that the process of oil burning may be more fully explained. It should not be understood that the cycle, or principle of the oil engine differs from that of any other engine, but that the vaporizer forms such a close connection with the engine proper that they must be described as one unit.
(43) Horizontal Single Cylinder Engine.
An example of a modern single cylinder engine operating on the four stroke cycle principle is the “Muenzel” engine shown in Section by Fig. 17. It is of the single acting type, that is, the pressure of the gases acts only on the left end of the piston which reciprocates in a horizontal direction. Surrounding the cylinder in which the piston slides, is the water jacket (shown by the short horizontal dashes) which keeps the cylinder walls from becoming overheated by the successive explosions of the mixture. The cooling water is pumped into the jacket through the pipe shown over the cylinder, and flows out of the jacket through an outlet near the bottom of the cylinder.
