The inertia forces due to can be nullified by placing appropriate balancing masses as indicated in Fig. 3.9. Thus the effective force transmitted to the frame due to rotating masses can ideally be made zero.

Figure 3.8 Counter balancing rotating masses

Figure 3.9 Opposed position configuration

However it is not so straight forward to make the unbalanced forces due to reciprocating masses vanish completely. As given in Eq. (3.7) and depicted in Fig. 3.2, there are components of the force which are at the rotational speed and those at twice this speed. It is conceivable to use a configuration as shown in Fig. 3.9 to completely balance out these forces but the mechanism becomes too bulky. Thus a single cylinder engine is inherently unbalanced.