International Shipbuilding Progress

A number of theoretical methods are derived in this paper for computing the natural frequencies of whirling vibration of shaft-disk systems including the consideration of rotatory inertia, gyroscopic precession and flexibility of shaft supports, as well as lumped and distributed masses.

Special emphasis is laid on the determination of the natural frequency as a function of the ratio of spin to whirl velocity. Natural frequencies are also expressed in terms of the spin velocity of the shaft. Particular attention is given to methods suitable for numerical evaluation. The methods given here are of special interest in applications to propeller-shaft systems of ships. Difference equations are given which have been used to code the general problem for solution with a UNIVAC computer.

A method for the calculation of stresses in the mast and stays of a stayed mast is developed.

Though the method is based on theoretical considerations some assumptions have to be made. These assumptions are discussed as well as the various doubtful factors involved in the calculation.

The various forces acting on the mast and the bending moments producing the deflection of the mast are considered.

The method of calculation is then explained and an attempt to justify the assumption on which the solution of the problem is based, is made in an appendix.

For design purposes, a method for estimating the maximum load in the stays and for determining their approximate sectional areas is discussed. A numerical example of this method is given in Appendix 2. Some references are given.