Abstract
Although it is now more than ten years since the first geared oil engine installation put to sea, no country other than Germany has made any serious attempt to exploit this method of propulsion. The success of Germany's geared ships has, however, completely proved the reliability of this type of drive, and has exploded the once prevalent belief that mechanical reduction gearing would not withstand the uneven torque of the oil engine.
The author first gives a brief historical survey of the geared oil engine ships at present in service, beginning with the original vessels of the Havelland class and finishing with Germany's “pocket” battleship Deutschland.
The advantages of incorporating reduction gearing are then dealt with, the author maintaining that the disadvantage of added weight due to the inclusion of gears is more than compensated for by the advantages resulting from smaller engines running at higher speed.
The types of drive in common use, namely, the rigid and the “Vulcan” types, are then described, together with the method of obtaining synchronized starting and reversing.
It is pointed out that, although torsional vibration problems disappear to a large extent with the “Vulcan” drive, they are of extreme importance in the case of rigid drives. A complete analysis of the question is therefore made at the end of the paper, and expressions are obtained from which may be calculated the natural frequencies of the normal types of installation. A worked example is included to show the application of these expressions.
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