Difference between revisions of "Balancing single/dual plane"

Depending on their rotational speed, two basic categories can be defined to classify rotors: <u>rotors with rigid shaft</u>, and <u>rotors with flexible shaft</u>. If the operating speed remains below half of the first critical bending speed, the shaft does not deflect : it may be considered as a rotor with a rigid shaft. At such operational speeds and due to the non circular cross section of the rotor, the axis of rotation and the inertial axis does not coincide (e.g. the mass is not evenly dispatched in a section of the shaft). This may results in a tumbling movement of the structure, which amplitude depends on the bearing clearance and stiffness. In any case, the bearings are subjected to unnecessary or even non allowed loads.  

At higher speeds the shaft will deflect, due to is own stiffness. In that case, it might be considered as a rotor with flexible shaft.  Depending on the position of the discs on the shaft they can even be inclined and thus create an oil whirl.<br>