On unstable vibrations of an asymmetrical shaft with fluctuating angular velocity. (3rd Report, gyroscopic action of a rotor driven through a universal joint)

A rotating speed of a shaft driven through a universal joint fluctuates periodically with even multiple of an angular velocity of the drive shaft. This paper deals with instability for inclinational vibrations of an asymmetrical shaft driven through a universal joint. For this rotor-shaft system, an unstable vibration caused by a shaft asymmetry occurs at an angular velocity near the major critical speed. As effects of the gyroscopic action become stronger, an angular velocity where this unstable vibration occurs increases. Furthermore, the other unstable vibrations caused by coexistence of a shaft asymmetry and an angular velocity fluctuation occur near half of the major critical speed. The number, the position and width of instability regions near half the major critical speed change remarkably with the effect of gyroscopic action.