REDUCTION GEARS FOR SHIP PROPULSION. 

 By Robert Warriner^ Esq., Member. 



[Read at a special meeting of the Society of Naval Architects and Marine Engineers, held in New York, 



May 26, 1921.] 



The past ten years have seen rapid development of the reduction gear for ship pro- 

 pulsion and something like one thousand merchantmen so fitted have been built or are 

 building. The venture has not been an unqualified success, but the proposition is attrac- 

 tive enough to warrant careful study and discussion so that the faults can be eradicated 

 and a reliable manufacture arrived at. 



The turbine, perhaps, is the simplest machine for turning the energy of steam into 

 power but its best efficiency and simplest construction are obtained with high speed of revo- 

 lution; on the other hand, the best efficiency of screw propeller is attained with compara- 

 tively low revolutions and to take advantage of the best in these two it is necessary to use 

 some means of reduction, either electric, hydraulic or gearing. 



The first application of reduction gear for ship machinery was on the S. S. Vespasian 

 by Sir Charles A. Parsons, and following this there were a few applications to special 

 steamers and cruising turbines for war vessels and the main drives for some destroyers. It 

 was not, however, until the shipbuilding activity which resulted from the war had attained 

 full swing and the urgent need for all kinds of machinery was felt, that the reduction gear 

 drive was made a leading type of propulsion machinery. 



The development was so rapid that most of this machinery was designed and built with 

 scant knowledge of the real requirements for sea service and with' none of the essential expe- 

 rience which comes from actual practice under continued service conditions. It should also 

 be remembered that the number of gear cutting machines was very limited and those in 

 use, with a few exceptions, were rather small, and no doubt this led to some reduction 

 gears being designed to meet the existing facilities for machining and cutting teeth. There 

 was also considerable trouble in getting special material and it was necessary to use what 

 was available. As a consequence there have been some unfortunate experiences which have 

 raised doubts in the minds of many engineers as to their ultimate success. On the other 

 hand, there are a number of examples where reduction gears are giving good service and 

 showing better economy than reciprocating engines tmder the same steam conditions, and 

 there is no doubt that by adopting a conservative design and manufacturing on soimd lines 

 this type of machinery can be made more reliable, economical and easier to handle than 

 other kinds of steam machinery. 



The Neptune, built by the Sparrow's Point Plant of the Bethlehem Shipbuilding Cor- 

 poration, was the first vessel of the U. S. Navy to be fitted with turbines and reduction 

 gears for main propelling machinery. The equipment was manufactured by the Westing- 

 house Machine Company (since consolidated with the Westinghouse Electric and Manufac- 

 turing Company) and the boat was put in commission in August, 1911. 



The economy of the machinery was not satisfactory and the contractor ofiFered to re- 



