Balancing is the process of attempting to improve the mass distribution of a rotor, so that it rotates in its bearings without uncompensated centrifugal forces. This is usually done by adding compensating masses to the rotor at prescribed locations. It can also be done by removing fixed quantities of material, for example by drilling.
Field Balancing is the process of balancing a rotor in its own bearings and supporting structure, rather than in a balancing machine.
Static Unbalance is defined as the eccentricity of the centre of gravity of a rotor, caused by a point mass at a certain radius from the centre of rotation (see Fig. 1). An equal mass, placed at an angle of 180° to the unbalanced mass and at the same radius, is required to restore the centre of gravity to the centre of rotation.
Static Balancing involves resolving primary forces into one plane and adding a correction mass in that plane only. Many rotating parts which have most of their mass concentrated in or very near one plane, such as flywheels, grindstones, car wheels, etc., can be treated as static balancing problems. If a rotor has a diameter of more than 7 to 10 times its width, it is usually treated as a single-plane rotor.