186 ELECTRIC AUXILIARIES ON MERCHANT SHIPS. 



In making- such comparisons it must be borne in mind that a cargo winch is at best a 

 compromise; in other words, for the reason that winches will be called upon to handle mis- 

 cellaneous cargo and that the length of the lift varies with the depth of the cargo in the hold 

 and the height of the dock or lighter on which the cargo is being handled, it will be necessary 

 for the owner or operator of the ship, with his naval architect and engineer, to arrive at a 

 design of winch which, all things considered, will be the best for the average conditions. In 

 larger ships with deeper holds it may be found desirable to somewhat increase the rope 

 speed and fit a larger motor. 



The horse-power rating of a winch motor is not definite. Electric motors are capable of 

 considerable overload for short periods of time. The rating will be considerably less if 

 based on a one-hour test rather than on one- half-hour test. Experience indicates that han- 

 dling cargo on ships gives approximately the same heating as a rated full load for the 

 half -hour. 



Mr. Jett also points out the need for more accurate data on fuel consimiption that may 

 be charged against ships' auxiliaries. The author wishes that Mr. Jett had put even greater 

 stress on this vital point. 



A reply to Mr. Smith's criticism would become very lengthy. He has given the subject 

 so much detailed thought and consideration that in the author's opinion a proper and fair 

 reply could only be made by discussing a number of specific cases in like detail with Mr. 

 Smith. In all fairness, however, it should be pointed out that, as stated in the introduction of 

 the author's paper, the comparisons were based upon cost of electrical equipment installed. 

 In all probability the individual units electrically driven will in many cases be somewhat 

 more costly than steam-driven apparatus of the same quality and for the same work. On 

 the other hand, the cost of installing the steam machinery with the extra piping will be con- 

 siderably greater than the cost of installing the electrical machinery, which requires only cable 

 to transmit the power from the engine room. The cost of $4,300, which Mr. Smith took 

 as the cost of an electric winch, is very high. Further, the cost of suitable electrically driven 

 ships' auxiliaries will be reduced as the demand increases. 



The author would point out that on the earlier motor ships steam-driven auxiliaries were 

 fitted, and it was found these required so much fuel that electric auxiliaries had to be fitted 

 in order to realize the high efficiency expected from a motor-driven ship. 



Mr. Smith's argument as to the amount of power that might be secured by admitting 

 7,950 pounds of exhaust steam to the low-pressure turbine is based on the assumption that 

 this is steam. When it is considered that a great part of the heat in the 12,500 pounds of 

 steam referred to in the author's paper has been given up to heating the atmosphere, that 

 condensation has been going on continuously in the thousands of feet of piping with approx- 

 imately 2,500 square feet of radiating surface, it must be recognized that there is a great deal 

 of hot water returned to the engine room and that the theoretical advantage cannot be 

 realized. 



If Mr. Smith will refer to the comparisons, he will find that the author allowed some- 

 what less for the auxiliary turbine when using 200 degrees superheat than with 75 degrees. 



It has not been the author's contention that steam machinery is of itself always inferior 

 to electrical. It is a question of application, and the future will show that it is not economical 

 to operate a number of small steam units distributed in different parts of a ship. When ship- 

 owners realize the gain that can be effected by substituting one steam engine driven, or even 

 oil engine driven generating set, for the multiplicity of small pieces of steam machinery, they 

 will fit their ships with electrically driven apparatus. 



