Rotational mass balance is another dimension of balance used by Victor
technicians. This differs from reciprocating mass balance, as this is only
the movement in the rotational direction as the engine propeller turns. This
mass is made up of the crankshaft, counterweights, gears, and large end of
the connecting rods, connecting rod bolts and nuts and factored for oil
weight. When engines are originally manufactured they are built using
theoretical balance procedures.
This assumes that when the parts are put into motion,
that they will remain balanced. In real time operation under load, the
balance changes and effective balance takes over. Over a period of time,
such imbalance could crack engine mounts, crankcases and exhaust systems,
cause premature bearing failure and propeller overloads, result in increased
engine temperatures and induce vibration in the cockpit. Additionally, an
engine imbalance can introduce harmonics in flight controls, instruments and
airframe members and is one of the leading causes of premature engine wear.
Balancing not only improves thrust but also reduces pilot and passenger
fatigue by lowering the amplitude of various vibration frequencies generated
by the engine.
