Dynamic Balancing:

While it is not possible to balance in the plane of unbalance, a situation might occur as illustrate in Fig 1(a). In this case, even if the forces are balanced by the following relation

                                                M₁  r₁  ω² = M  r ω²

a couple shall act which causes overload of the bearings. In order to balance the mass M, one more balancing mass will be mounted on the other plane to neutralise the couple also. So, in the dynamic balancing two balance planes are needed to neutralise centrifugal force alomg the couples as illustrated in Figure 1(b).

(i)                                                             (ii)