ELECTRIC PROPULSION OF SHIPS. 109 



unsettled conditions. On the basis of equal performance in regard to propeller torque and 

 speed, the cost, including all items related to the propulsive equipment, should run in the 

 order of direct Diesel, turbine electric, geared turbine and Diesel electric, the latter being 

 the cheapest. The paradox in the relative cost of direct Diesel and Diesel electric is explained 

 by the condition that small Diesel engines and generators for Diesel electric drives can be 

 manufactured ultimately on a large production basis and stocked, whereas the engines for 

 direct Diesel drive and, to a large extent, the two types of turbine drive, because of their 

 large size and weight, must almost of necessity be a building proposition. On the basis of 

 standardized drives there should not be a great deal in favor of the geared turbine as com- 

 pared with the turbine-electric drive. This comparison will vary somewhat with the different 

 manufacturers. 



The initial cost of the propulsive equipment has a direct effect upon the net earning 

 power of the ship, because of interest, depreciation and insurance charges, and therefore cost 

 is an important item. 



Operation. — In regard to operation, it is realized that the present operators are largely 

 men who are more familiar with reciprocating engines than with other types of machinery, 

 and that for this reason certain difificulties are likely to be encountered in placing electrical 

 equipments in their hands. The author believes that this thought should not be a considera- 

 tion, as it is a temporary condition only. The horse-car driver became the motorman of the 

 electric car, the reciprocating plant operator became the turbine plant operator in the central 

 station, the steam locomotive engineer became the electric locomotive engineer (engineers 

 now operating electric locomotives are reluctant to return to the steam locomotive), and 

 similarly coimtless examples may be mentioned to show that change in machinery repre- 

 sents no obstacle. Successful operators of electrical machinery need not have sufficient knowl- 

 edge of it to understand the details of its design. This is not the case on land, and there 

 is no greater reason for it on the sea. The operator should, however, know the operating 

 characteristics of electrical apparatus and how to take care of it. 



The same question was raised in the case of geared turbines only a few years ago, yet 

 today there is nearly a sufficient number of competent geared-turbine operators to take 

 care of all the geared-turbine ships. The same will be the case with operators for electric ships. 

 It is merely a matter of training and education, and it is certainly a reflection upon the 

 intelligence of the age to classify the present limited knowledge as an obstacle for consideration. 



On page 110 is a probable list of the operating personnel for the principal types of 

 drives. The cost of operating personnel as based upon this list would therefore be in the 

 order of direct-connected Diesel, turbine electric, geared turbine, reciprocating engine, and 

 Diesel electric. 



Maintenance. — Although there are practically no data available on the maintenance 

 of electrical propulsive equipments (except battleships), there is no reason to anticipate any 

 great difference between sea and land practice. As a matter of fact, there is reason to antici- 

 pate less maintenance for the reason that the load conditions and control operations are less 

 severe than is the case with most land installations involving large machinery. If the equip- 

 ment is given proper care and inspection, the maintenance item will be low, as the absence of 

 rubbing parts (except for the bearings) leaves little to get out of order. Electrical machinery 

 does not wear as is the case with other machinery. Furthermore, all probable repairs are such 

 as can be made aboard the ship without the use of an elaborate machine shop. 



Performamce Characteristics. — The inherent performance characteristics of electrical 

 machines are particularly well suited to ship propulsion. Having identical operating char- 



