PROGRESS IN TURBINE SHIP PROPULSION. 87 



dimension of fixed bearing gears forming the basis of the other curves are quite authentic, 

 the data having been furnished "by correspondents abroad." Mr. Anderson is in grievous 

 error if he supposes a breach of confidence has been committed in publishing the curves, all 

 of which is, however, a matter of irrelevance. It would have been of interest, and more 

 relevant, had he submitted instances, if he knew of them, of fixed bearing gears in service 

 which regularly operate with tooth pressures different from those I have given. 



Mr. Anderson is in error in his conclusions concerning the 22,000 horse-power gear. 

 The curve is perfectly correct in this respect, the 22,000 horse-power being transmitted by 

 two pinions and not by four, as he supposes. 



Answering Mr. Anderson's question, pinions in excess of 12.3 inches pitch circle di- 

 ameter have not yet been constructed. Several have been projected of larger dimensions whose 

 diameter referred to tooth pressure would fall substantially on the curve. It was thought 

 proper to limit the points of the curve in the paper only to gears that were in actual service. 



Mr. Anderson's apparent assumption that the Westinghouse Company use practically 

 a constant pitch of teeth is erroneous, for in all pinions there are practically a constant num- 

 ber of teeth, their pitch varying with the size of pinion. He refers also to the angle of helix 

 employed by different manufacturers which vary all the way from 23 degrees to 45 degrees, 

 the selection of which is the subject of careful consideration by the designer, who must 

 choose an angle to secure maximum strength on the one hand, and a sufficient degree of 

 smoothness of operation on the other. As the problem is to obtain the highest safe power per 

 revolution per minute from a given diameter of pinion, the curves are quite comparable what- 

 ever are the details of the pitch of teeth or angle of helix. 



While it is perhaps improper to discuss events which have occurred since the writing of 

 the paper, it is of interest to state that some quite serious difficulties have been encountered 

 with some gears being installed in cargo ships by the Westinghouse Company, these troubles 

 having developed during manufacture and installation, and not in operation after the vessels 

 had been placed in service. They were due, in part, to an unfortunate selection of form of 

 involute tooth, and in part because of some execrable workmanship, the result of war-time 

 labor conditions with a new factory and organization. Further, the stress to make delivery 

 caused thorough shop tests to be foregone, and indeed previous experience with a large num- 

 ber of entirely successful gears did not indicate full-power and full-speed tests at all neces- 

 sary. The whole point in referring to this matter is to state that these troubles have plainly 

 indicated to us that floating frame gears may be designed for a much higher power constant 

 than was hitherto thought possible, and there is no doubt that in the near future gears will 

 be designed to operate with tooth pressures far in excess of that shown by the curve in the 

 paper. 



Mr. Anderson's supposition that it has been considered desirable to use a separate oil 

 for the gear is of course without foundation. The author would certainly regard an instal- 

 lation which employed two oil systems as very undesirable. 



I do not follow Mr. Anderson in his remarks concerning maneuvering valves. His pref- 

 erence savors to me to be borne of a desire to take the path of least resistance instead of 

 designing apparatus to be the most adaptable. Two separate globe valves, one for ahead, 

 and the other for astern operation, both of which may be open at the same tirne with un- 

 fortunate results, could hardly seem to bear comparison with a carefully designed maneuver- 

 ing valve, having convenience and adaptability in view, and which precludes the above possi- 

 bility. His stated reason that the two separate valves gives the operating engineer more to 

 do does not seem to be sound. 



