120 ELECTRIC PROPULSION OF SHIPS. 



Reliability. — In all phases of the industrial field where electricity has entered, it has 

 proven its reliability. With a good record for reliability behind it, electricity has set out 

 to establish a similar record on the sea, and the experience of the two large battleships thus 

 far equipped with electric propelling machinery, and in service, shows that there will be a 

 duplication of past satisfactory performance. The electrical machinery will be found to be 

 in good condition long after the ship has become obsolete. 



The arrangement of units and distribution of power make it possible to supply balanced 

 power to all screws in the event of casualty to one of the prime movers. In other words, the 

 electric drive possesses an inherent advantage in regard to reserve power. 



Economy. — Regardless of calculations, the recorded performance of the electrically pro- 

 pelled battleship New Mexico has proven the superiority of the electric battleship in respect 

 to fuel consumption. Recently published figures in the Marine Review show that the Idaho 

 and Mississippi use 20 per cent more oil at 10 knots than the New Mexico, 42.7 per cent more 

 at 13 knots, 48 per cent more at 16 knots, 40.1 per cent more at 19 knots, and 32 per cent 

 more at full power. This superiority in fuel consumption is not altogether due to the main 

 units, as the figures include the oil consumed by the auxiliaries. There is enough difference, 

 however, to show conclusively that the comparison is very favorable to the electric ship. 



That the advantage in fuel consumption demonstrated by the New Mexico is not a mere 

 incident, it is well to note that the Tennessee, which is a later ship, is showing even better 

 results than the New Mexico, as was indicated when the two ships steamed together during 

 recent maneuvers of the Pacific fleet. Accurate measurement of unit fuel consumption dur- 

 ing the official trials of the Tennessee showed that the actual steam consumptions were less 

 than the guaranteed figures by amounts varying from approximately 3 to 8 per cent. Thus 

 the art of electric propulsion is still progressing. The answer is found in the use of only 

 a sufficient number of turbines for the load conditions and in the two speed motors, the com- 

 bination of which maintains a higher average load on the turbines at a higher average speed. 



Maneuvering. — Owing to the availability of full backing power in the case of the elec- 

 tric-drive ship, the latter possesses a marked advantage over the turbine ship in maneuvering 

 qualities. As these were referred to under "Merchant Ships," it is sufficient to merely men- 

 tion at this time that the electric battleship can be stopped in considerably less time than is 

 required to stop a turbine ship. The advantage of this feature is obvious in the case of a 

 war vessel. This is due to the combined action of quicker "set-ups" and greater backing 

 power. 



Further maneuvering advantages of the electric drive are apparent from recent publica- 

 tions. These advantages are chiefly concerned when entering and leaving ports and maneu- 

 vering therein. By operating the ship from one turbine set, the other, or others if there are 

 more than two, can be held in readiness for immediate service in case of necessity such as 

 would arise from a mudded condenser or other cause. When maneuvering to get tinder 

 way, operation from a single generating set inherently enables exactly the same speed — but 

 of opposite direction — to be obtained on the port and starboard screws. This is very desir- 

 able for the reason that the ship can be turned on its heel without making any headway. With 

 different prime movers supplying power to the various screws, it would be difficult to main- 

 tain all the screws at the same speed and thereby turn in the same space. 



Control. — The control for the propelling machinery is centralized in one compartment 

 and can be easily arranged to be operated by one operator. The flexibility of the control is 

 such that almost any emergency resulting from casualty to any equipment connected with 



