84 SOME COMPARISONS RELATING TO 



I do not agree with the author or Lieutenant Robinson that the greatest test of the satis- 

 factory working of any machinery is whether or not the men who are actually handling it and 

 caring for it are pleased with it. 



Such a test is of vital importance, but the greatest test is the one which interests the 

 shipowner ; that is, how does this type of machinery compare with other methods as regards 

 coal consumption, cost of operation, and upkeep? 



Fig. 2, Plate 41, shows that the Jupiter burns a large amount of coal, and I think oper- 

 ating costs must be and will always continue to be very heavy, as specially trained electrical 

 engineers are required to operate the machinery. 



The data published by the author giving the contract conditions of the California are 

 specially interesting to marine engineers, and I think the General Electric Company has 

 remarkably easy conditions to fulfil. The only point I am not clear about is what is meant 

 by maximum speed. If no definite speed is given in the contract, then the conditions of the 

 high-speed test are simplified. The penalties to be imposed if the guaranteed steam consump- 

 tions are exceeded on the various trials would not cause me any uneasiness, as shaft horse- 

 power is very much a variable quantity. 



The weight figures given amuse me. Nothing can be gained in discussing this point, as 

 both sets of figures are estimates, and probably the comparisons may not be just. 



Mr. Emmet points out that 21 knots speed of 175 revolutions for the propeller 

 wheels is about the lowest which is practicable for the space available. I hardly think 

 these propellers will give the California an advantage of 9 per cent over the other ships at 

 240 revolutions, for the strut brackets which support the propellers will have to be exceed- 

 ingly long, and I am strongly of the opinion that this will cause considerable vibration. Back- 

 ing at full speed and full revolutions will hardly be possible, as the chances of causing damage 

 to the ship's structure at the stern of the vessel will be great. 



I have prepared a lantern slide (Plate 42) of a four-shaft all-geared turbine machinery 

 arrangement for a U. S. battleship having similar dimensions to the California, and it was 

 very disheartening that the Navy Department did not see their way to consider such a pro- 

 posal at the time that the California estimates were in course of preparation. The New York 

 Shipbuilding Company, Camden, N. J., submitted a bid to the Navy Department last year 

 for a four-shaft all-geared turbine installation in a battleship, and this bid was lower in cost 

 than alternative proposals with other direct-driven turbines. 



There are four independent sets of turbines together capable of developing 32,000 shaft 

 horse-power at 200 revolutions of the propeller wheels, giving a speed of 21 knots to the 

 vessel, and under maximum conditions a speed of 22 knots will be possible. 



The leading advantages of such an installation are as follows : — 



First, good economy at full power and cruising powers. 



Second, the calculated weights of the turbines and gearing amount to 380 tons, making 

 a large saving when compared with electric or direct-driven type. 



Third, independent control of each shaft, and it is practically impossible to put such a 

 machinery installation hors de combat. 



Fourth, nothing about an installation of this type can be regarded as experimental. Its 

 success is a foregone conclusion. The total power of each shaft corresponds to the power 

 developed by each shaft of the twin-screw geared turbine destroyer Wadsworth completed by 

 the Bath Iron Works, Bath, Maine, this last summer, and this vessel is showing remarkably 

 fine economy in commission. (Reference: — Journal of the American Society of Naval 

 Engineers, August, 1915.) 



