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The newly revised edition of this material contains significant improvements and updates.

 

The development of propulsion gearing has been one of continuous improvement and refinement in materials and in manufacturing techniques and equipment to provide greater reliability and longer life. The power ratings of gears have increased to keep pace with the requirements for larger and faster ships. There are only a few step-advances that can be identified, the step from single to double reduction, the introduction of welding to the construction of gear wheels and casings, the introduction of higher hardness pinion and gear materials with the attendant higher gear tooth loadings, and the subsequent refinement of surface hardening methods (carburizing and nitriding) as an alternative to through-hardening gear teeth. The reliability, high efficiency, and long life of the modern reduction gear are well known, and its low noise level makes it completely acceptable in the engine room. These factors have been in large part responsible for the continuing popularity of the geared-turbine drive for ships.