Two alternative methods are presented by the authors for the determination of torques in the propelling machinery of ships when friction is taken into account. One is called the “direct method,” while the other is called the “method of normal coordinates.” The latter is described at length, showing the great saving of numerical work possible by its use when compared to the direct method.

The paper points out that at critical propeller speeds oscillatory torques are limited only by damping. Two types of damping are taken into account: One is damping of the propeller in water; the other is friction in the driving mechanism, introduced as solid friction in the shafts similar to damping in the metal.

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