Tham khảo tài liệu 'dynamics of mechanical systems 2009 part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 532 Dynamics of Mechanical Systems Here we see that both the resultant primary and secondary inertia forces are also balanced leaving the only unbalance with the resultant primary moments. Thus we have still further improvement in the balance. These examples demonstrate the wide range of possibilities available to the engine designer however the examples are not meant to be exhaustive. Many other practical configurations are possible. The examples simply show that the crankshaft configuration can have a significant effect upon the engine balance. In the following section we will extend these concepts and analyses to eight-cylinder engines. Eight-Cylinder Engines The Straight-Eight and the V-8 If we consider engines with eight cylinders the number of options for balancing increases dramatically. The analysis procedure however is the same as in the foregoing section. To illustrate the balancing procedure consider an engine with eight cylinders in a line the straight-eight engine and with crank angles ội for the connecting rods arranged incrementally at 90 along the shaft. Table provides the listing of the ội for the eight cylinders i 1 . 8 together with the trigonometric functions needed to test for balancing. A glance at the table immediately shows that the engine with this incremental 90 crank angle sequence has a moment unbalance. This raises the question as to whether there are crank angle configurations where complete balancing would occur within the approximations of our analysis. To respond to this question consider again the four-cylinder engine of the previous section. For the crank angle configuration of Table we found that the four-cylinder engine was balanced except for the primary moment. Hence it appears that we could balance the eight-cylinder engine by considering it as two four-cylinder engines having reversed crank angle configurations. Specifically for the four-cylinder engine of Table the crank angles are 0 90 270 and .
