Balancing is the process of eliminating or at least reducing the ground forces and/or moments. It is achieved by changing the location of the mass centres of links. Balancing of rotating parts is a well known problem. A rotating body with fixed rotation axis can be fully balanced i.e. all the inertia forces and moments. For mechanism containing links rotating about axis which are not fixed, force balancing is possible, moment balancing by itself may be possible, but both not possible. We generally try to do force balancing. A fully force balance is possible, but any action in force balancing severe the moment balancing.
BALANCING OF ROTATING MASSES:
The process of providing the second mass in order to counteract the effect of the centrifugal force of the first mass is called balancing of rotating masses.
1 Static balancing:
The net dynamic force acting on the shaft is equal to zero. This requires that the line of action of three centrifugal forces must be the same. In other words, the centre of the masses of the system must lie on the axis of the rotation. This is the condition for static balancing.
2 Dynamic balancing:
The net couple due to dynamic forces acting on the shaft is equal to zero. The algebraic sum of the moments about any point in the plane must be zero.
3 Various cases of balancing of rotating masses:
¨ Balancing of a single rotating mass by single mass rotating in the same plane.
¨ Balancing of a single rotating mass by two masses rotating in the different plane.
¨ Balancing of a several masses rotating in single plane.
¨ Balancing of a several masses rotating in different planes.