less. With the off-set construction, as shown at D, it will be noticed that with the same connecting rod length as shown at C and with the crank shaft at 90 degrees of the circle that the connecting rod angle is 14 degrees and the side thrust is reduced proportionately.

Fig. 63.-Diagrams Demonstrating Advantages of Off-set Crank-Shaft Construction.

Another important advantage is that greater efficiency is obtained from the explosion with an off-set crank shaft, because the crank is already inclined when the piston is at top center and all the energy imparted to the piston by the burning mixture can be exerted directly into producing a useful turning effort. When a cylinder is placed directly on a line with the crank shaft, as shown at A, it will be evident that some of the force produced by the expansion of the gas will be

exerted in a direct line and until the crank moves the crank throw and connecting rod are practically a solid member. The pressure which might be employed in obtaining useful turning effort is wasted by causing a direct pressure upon the lower half of the main bearing and the upper half of the crank-pin bushing.

Very good and easily understood illustrations showing advantages of the off-set construction are shown at E and F. This is a bicycle

crank hanger. It is advanced that the effort of the rider is not as well applied when the crank is at position E as when it is at position F. Position E corresponds to the position of the parts when the cylinder is placed directly over the crank-shaft center. Position F may be compared to the condition which is present when the off-set cylinder construction is used.

Influence of Cylinder Construction on Engine Design.-To show the manner in which the various methods of casting cylinders previously

Fig. 66. Sectional View Knox Model R Motor, Illustrating Application of Individual Cylinder Castings, Separable Head Members and Five-I earing Crank Shaft. A Simple and Substantial Design that is Enduring and Efficient.

defined may alter engine design some views of typical power plants are presented. That at Fig. 64 is a part sectional view of the Sheffield Simplex, an English six-cylinder motor. In this the cylinders are cast in blocks of three, and the motor is composed of two blocks. A seven-bearing crank shaft is used, there being a journal between each pair of cylinders in addition to the two end members. A feature of this power plant that may be commended is the exceptionally good water jacketing of the cylinders. The water spaces are large and all parts of the cylinder are surrounded by cooling liquid.

Fig. 67. Sectional View of Typical Four-Cylinder Motor Using Individual Cylinder Castings with Cylinder Heads Cast Integral. General Design Fair, Excepting that of Connecting Rods.

At Fig. 65 a section through a typical four-cylinder block motor is given. In this power plant a short crank case is used, but the crank shaft is supported on three bearings instead of two journals as is common practice with four-cylinder motors. To show the use of indi