The Mechanics of Bearing Supports

The general problem of flexibility of supports is investigated analytically. It is shown that geometrically symmetric supports are also elastically symmetric, leading to reduced rotor vibration problems. The 90-deg, two-armed support also is shown to be elastically symmetric. Small departures from the 90-deg spacing, however, are shown to lead to serious lack of elastic symmetry. The simple pedestal is shown to be incapable of being designed with elastic symmetry. The symmetric support is shown to induce fewer blade-excitation frequencies in turbomachines.