Vertical balancing machines
Vertical axis balancing machines are normally used for balancing rotors with centre bores and outer diameter larger than the axial length, for example flywheels, pulleys, pump impellers, grinding wheels, car wheels, brake discs, clutches and similar components.
Modern vertical axis machines have a hard bearing force measuring system, with such a structure that the rotational frequency is less than a third of the resonance frequency of the rotor mounted on the machine spindle. As a consequence the vibration of the spindle during rotation is very small, and a very robust and reliable piezoelectric force transducer measures the centrifugal force due to the unbalance. The machine is therefore permanently calibrated in grams or grams per millimetre, independently of the rotor mass and its rotation speed, provided that these parameters are kept within the limits specified by the manufacturer.
Vertical axis balancing machines are available in one plane configuration for the measurement of the static unbalance only, and in two planes configuration for the measurement of the dynamic unbalance.