52 ENGINEERING PROGRESS IN THE U. S. NAVY. 



The question of costs of the different types of machinery will not be 

 considered in comparing the relative advantages of the types. 



Further, the relative values of turbine reduction gear, electric propulsion 

 and internal combustion engines for propulsion will not be dealt with, for 

 the following reasons: — The turbine reduction gear and electric propulsion 

 are under trial in the naval service at the present time, the reduction gear 

 being actually afloat while the vessel fitted with electric propulsion is building. 



The results obtained up to date with the reduction gear have been dis- 

 appointing so far as the expected economy is concerned, the results being 

 vitiated by faulty turbines and too high a number of revolutions of propeller, 

 135 per minute, for the type of vessel and the speed, 14 knots. The reduc- 

 tion gears have, however, stood up to the work well and show practically no 

 evidences of wear. Results are encouraging and a great improvement is 

 expected when contemplated changes in the turbine have been made. 



Electric propulsion not having been tried out in actual service, it is con- 

 sidered preferable to content ourselves with the mere statement that shop 

 tests of one of the units have been very gratifying and promise a successful 

 end to the experiment, so far as economy of propulsion only is considered. 



As to the question of propulsion by internal combustion engines, where 

 large powers are required, there appear still to be many important problems 

 requiring solution before units of sufficiently high powers for the purpose 

 desired can be built. The supplanting of the steam-engine, both reciprocat- 

 ing and turbine, for important high-power installations does not appear to 

 be imminent in the immediate future. 



Eliminating these three latter methods of propelling naval vessels 

 restricts the choice of machinery for this purpose to the three following 

 methods : — 



1. By means of reciprocating engines. 



2. By means of steam turbines, impulse, reaction, or a combination of 

 the two. 



3. By means of various combinations of reciprocating engines with 

 turbines. 



COMPARATIVE SUITABILITY OF EACH OP THE ABOVE METHODS FOR 



NAVAL PURPOSES. 



To assist in reaching a decision as to which of the three methods of 

 propulsion best meets the requirements lettered from (a) to (i) , a compari- 

 sion of the performances of the dreadnoughts Delaware, North Dakota, 

 Utah, and Florida can be made; these performances include those on pre- 

 liminary acceptance trials and those in actual service. 



