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Difference between revisions of "Balancing single/dual plane"
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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 (Z) and the inertial axis (Δ) 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. | 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 (Z) and the inertial axis (Δ) 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. | ||
[[Image:Unbalanced_shaft_schem.png|framed| | [[Image:Unbalanced_shaft_schem.png|framed|center|''Unbalance : inertial axis does not coincide with rotational axis'']]<br> | ||
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> | 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> | ||