Q. What can be done to increase flywheel speed without danger?

A. The flywheel may be made of a stronger material, such as steel, if it is desirable to retain the same diameter, or it may be made smaller in diameter if made of cast iron.

Q. Describe simplest type of flywheel.

A. The simplest form of flywheel consists of a web having a heavy rim or a simple cast hub joined to a heavy rim member by a series of radiating arms or spokes which are cast integral with the hub and the rim.

Q. What is the advantage of web wheels?

A. The web wheel is a safer method of construction and is also stronger than the spoke type. When a flywheel of the spoke type is turning at a high rate of speed it will do considerable injury to any object inadvertently thrust between the spokes. As the web construction makes practically a solid flywheel it is not possible to catch anything in the wheel.

Q. Why are flywheel spokes sometimes shaped like fan blades?

Fan blades are often incorporated in flywheels so that member acts as a fan or blower to induce a draft of air through the radiator of a water cooled engine or around the cylinders of an air cooled type.

Q. How are clutches attached to flywheels?

A. Cone clutches have the female members recessed in the flywheel interior, while multiple disc clutches or those of the expanding band type are housed in a drum or casing either machined with the flywheel casting or attached thereto by some method of mechanical fastening. Three and five plate clutches are carried on simple stud members screwed into the flywheel.

Q. How are flywheels attached to crankshafts?

A.

Flywheels are attached to crankshafts either by means of a taper shaft and key retention or by means of bolting it when of the web type to a flange formed integral with the crankshaft. The latter is the preferred construction.

Q. Why must flywheels be securely fastened?

A. 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. Q. What is the meaning of marks on flywheel rims?

A. The marks placed on flywheel rims, as indicated at Fig. 39, 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 crank shaft position when the piston in the cylinder being timed is at the bottom of its stroke.

Q. What influence does flywheel diameter have on spacing of timing marks?

A. For a given number of degrees crank travel the marks are farther apart on large diameter flywheels than they are on those of lesser radius.

Q. What are the manifolds?

A. 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.

Q. How are they secured to cylinders?

A. 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.

Q. What precautions must be observed when designing manifolds?

A. Inlet or fresh gas manifolds should always be proportioned so that the gas from the carburetor does not have to turn any sharp corners and so the distance between each valve chamber of a multiple cylinder engine and the carburetor will be approximately the

same.

Exhaust manifolds should cffer a free passage to the escaping gas and should be large enough in bore so that there will be no friction between the gas stream and the manifold wall.

Q. How is the engine base attached to vehicle frame?

A. The common method of construction is to cast arms integrally with the engine bed which extend to the main frame sides or rest on an inner frame or sub-frame member that is in turn supported by the main frame.

Q. What is the three point support"?

A. If the power plant is supported by three points placed in relation to each other so that the two on the same line form the base of a triangle while the third forms the apex, the engine is said to have a three point support. The advantages of this construction may be readily understood if one compares the action of a three legged stool and one having four legs on uneven ground. The stool with the three point support is not so much affected by irregularities in the surface on which it rests as is the four legged member. A power plant supported on three points is not affected by frame distortion or springing out of alinement as much as a four point support power plant.

Q. What is "four point support"?

A. When a power plant is held in place in the frame by means of four arms so that the point of support forms a rectangular figure, the engine is said to have four point support. The four point system necessitates the use of a more rigid frame than does the three point method of suspension.

Q. What is a unit power plant?

A. The unit power plant construction is that where the engine, clutch and gearset are attached together so these three members may be said to be supported by the same common carrier or case. A unit power plant with the three point support is commonly used in motor car construction.

Q. What are the advantages of the unit power plant?

A. One of the methods of installing the motor and gearset of an automobile is to attach these to a frame as separate members and