Six Cylinder Buick rotary movement suitable for turning the wheels of the automobile. The crank case is utilized to support the crankshaft and to act as a bed for the engine cylinders. It keeps the working part of the cylinder in perfect alignment with the crankshaft and camshaft carried and protected by the crank case, and at the same time it serves as a carrying or supporting member by which the power plant is attached to the chassis. Automobile engine crank cases may be made of cast aluminum, cast iron, or bronze castings. The first named material is most generally used on account of its lightness. It has about the same strength as cast iron and weighs but one-third as much. On engines that are manufactured in large quantities, stamped sheet metal, such as steel and aluminum, have been utilized as the lower portion of the crank case. The small auxiliary shaft that carries the valve lifting cams and usually runs parallel with the crankshaft and which is driven by that member is called the camshaft. Some engines have but one camshaft, which carries the cams utilized in operating both inlet and exhaust valves. The "L" type cylinder engine needs but one camshaft, while the power plant provided with "T" head cylinders needs two camshafts, one at each side of the motor. The camshaft of a four-cycle engine is always driven at half the engine speed and always by positive gearing. A cam is a cylinder of metal having a raised portion at one point on its periphery. The difference between inlet and exhaust cams is in the cam profile, as * the member intended to lift the exhaust valve has a longer dwell or larger and longer raised portion because the exhaust valve is kept open longer than the inlet member. The manifolds are the built-up members or pipes that convey the fresh gas from the carbureting device to the valve chambers or which convey the inert products of combustion from the exhaust valve chambers to the muffling device. Manifolds are usually attached to cylinders by means of flange couplings bolted to the cylinders or by stirrups or retention bars which hold them securely in place. Part Sectional The flywheel is a heavy member attached to the crankshaft which has energy stored in its rim as the member revolves, and the momentum of this revolving mass tends to equalize the inter Fig. 8.-Plan View of the Dort Four Cylinder Chassis, Showing Important Parts of the Mechanism and Their Relation to Each Other. mittent pushes on the piston head produced by the explosion of the gas in the cylinder. If some explosive is placed in the chamber formed by the piston and closed end of the cylinder and exploded, the piston would be the only part that would yield to the pressure which would produce a downward movement. As this is forced down the crankshaft is turned by the connecting rod, and as this part is hinged at both ends it is free to oscillate as the crank turns, and thus the piston may slide back and forth while the crankshaft is rotating or describing a curvi linear path. It is imperative that flywheels be attached firmly to the crankshaft, because any looseness between the flywheel and the shaft will produce a pronounced knocking sound, and the methods of fastening, such as keys or bolts, may be entirely sheared off. The marks on flywheel rims are placed thereon to assist in timing the valves and ignition spark. The abbreviation E. O. means "Exhaust Opens," while E. C. means "Exhaust Closes." The letters I. O. mean "Inlet Opens," while I. C. means "Inlet Closed." The letter S. indicates the sparking point, while U. C. means "Upper Center," which means that the piston is at the top of its stroke, and L. C. means "Lower Center," which corresponds to the crankshaft position when the piston in the cylinder being timed is at the bottom of its stroke. The numbers in connection with the marks indicate the cylinders in which the functions marked should be taking place. In addition to the simple elements described it is evident that a gasoline engine must have other parts. The most important of these are the valves, of which there are two to each cylinder. One closes the passage connecting to the gas supply and opens during one stroke of the piston in order to let the explosive gas into the combustion chamber. The other member, or exhaust valve, serves as a cover for the opening through which the burned gases can leave the cylinder after their work is done. The spark plug is a simple device which permits one to produce an electric spark in the cylinder when the piston is at the best point to utilize the pressure which obtains when the compressed gas is fired. The valves of each cylinder open one at a time, the inlet |