74 SOME COMPARISONS RELATING TO 



DISCUSSION. 

 The President : — This paper by Mr, Emmet is now open for discussion. 



Mr. John Platt, Member: — The remarks that have just been made by Mr. Emmet in 

 regard to his paper that refer to some of the illustrations that go with his paper, I presume 

 cover the case and may take away from something I am going to say ; but as he has written 

 his paper and published these illustrations in his paper, and as they form part of the paper, I 

 take it that it will be in order if I give a few facts with regard to the designs of turbines 

 with mechanical reduction gear, particularly those to which he refers in the paper. 



In the fourth paragraph, p. 71, Mr. Emmet tells us that the award of this contract for 

 the California was the result of a very long campaign of education and further refers to the 

 collier Jupiter, the only marine installation of electric reduction gear under this system that 

 at present exists. The author seems to think he has been a very long time in getting recogni- 

 tion. It seems to me he really should be very much gratified to have obtained so quickly the 

 opportunity of trying out this form of drive in a fifteen-million-dollar battleship. In spite of 

 the fact that there are some twelve million horse-power of Parsons marine turbines in differ- 

 ent parts of the world, and three million horse-power with mechanical reduction gear, 

 the Navy Department did not consider the use of this most successful mechanical reduction 

 gear in the proposals submitted by the navy yards for the propelling machinery of the two 

 newest battleships. 



In the last paragraph on page 72, the revolutions of the California propellers are given as 

 175 per minute. This number of revolutions the author contrasts with the 240 revolutions 

 of the direct-driven Parsons turbine ship Idaho, and concludes that there is an advantage 

 to the electric reduction gear of about 9 per cent in propeller efficiency. This he derives 

 from Dyson's method. It should, however, be unnecessary to point out that to make the 

 comparison useful to engineers and shipbuilders the 175 revolutions of the California should 

 be compared with the 200 revolutions used in the Parsons layout with mechanical-reduction 

 gear. 



The first paragraph on page 73 compares the expected steam consumption on the Cali- 

 fornia with that of the Florida and Utah fitted with Parsons turbines. The author then 

 states that the figures given in the table "afiford the truest basis of comparison of prime 

 movers in ships." This would be true if the ships were of equal size, and if the Florida 

 and Utah were fitted with reduction gear. Surely the author does not expect the members 

 of this Society to agree with him that a comparison such as he proposes is a proper one. 

 The Florida and Utah are older ships, are of 50 per cent less displacement, with the straight 

 drive, and with no reduction gear. 



In the fifth paragraph we are referred to the illustrations that accompany this paper. 

 We are told that Plate 37 is "the California," but that the arrangement shown is not the one 

 which will be used. If comparisons are to be made, may we not properly ask that the ma- 

 chinery that is actually to be used in this ship be illustrated in the Transactions of the 

 Society in place of the arrangement shown in the advance copy? 



In Plate 38 he illustrates the turbine and piping arrangement of the Utah, and in Plate 39 

 what he calls "a geared turbine equipment for a large warship shown in a paper by Sir 



