174 ELECTRIC AUXILIARIES ON MERCHANT SHIPS. 



mation as to speeds at which cargo is handled by steam winches. I have made an extensive 

 study of this subject, and it is my opinion that only in exceptional cases is a rope speed of 

 250 feet a minute reached in handling sling loads of cargo even as light as 1,000 pounds, but 

 the items of greatest importance are the acceleration and the speed of raising and lowering 

 light hooks. In the design of electric cargo winches, in deciding on the size of the motor, 

 you must take into consideration the speed at which the various weights of cargo are to be 

 handled. 



I do not agree with Mr. Dickinson's recommendations as to the size of motors required 

 for deck winches on 8,000 to 10,000-ton cargo ships. In my opinion 25-horse-power motors 

 are ample for any cargo winch except in case of very deep holds of the largest vessels. The 

 majority of 8,000 to 10,000-ton deadweight vessels have but eight steam winches, usually 

 with engine cylinders of 8j4 inches by 8 inches or the equivalent. It has been demonstrated to 

 my entire satisfaction that an electric winch equipped with a 25-horse-power series direct- 

 current motor will more than equal in every respect the performance of an 8j4-inch by 10- 

 inch steam cargo winch. It is my belief that the load factor or ratio of average to maximum 

 load, and consequently the size of winch motors required, is overestimated. 



Referring to Mr. Dickinson's comparison between electric and steam operated auxilia- 

 ries as to fuel consumption, because of the many elements to be considered, it is very difificult 

 to determine the possible fuel saving to be effected in the operation of the engine-room auxili- 

 aries, this being a matter on which there are very little accurate data available. Advocates 

 of steam equipment will no doubt take exception to the figures presented in Mr. Dickinson's 

 paper. An important item to be considered in this connection is the fact that electrically op- 

 erated equipment can be maintained at a higher operating efficiency than steam equipment. 

 Electric motors will continue to operate at practically maximum efficiency as long as continued 

 in service, as compared with steam equipment, which is subject to the usual adjustment and 

 wear of steam valves, wear in cylinder liners, broken or loose piston rings, condition of steam 

 packing, etc. The figures presented by advocates of steam equipment would of course be 

 based on the equipment being in its most efficient operating condition, which is not generally 

 maintained in service. 



In my opinion Mr. Dickinson has been entirely too conservative in his estimate of the 

 possible economy of electric deck winches over steam equipment, both in the case of fuel for 

 operation and repair costs. There are considerable accurate data available on this subject. 



The following data were obtained as a result of recent carefully conducted tests under 

 actual operating conditions on a vessel of 11,600 tons deadweight equipped with three Scotch 

 boilers, oil fired; main propulsion electric drive; engine room and deck auxiliaries steam 

 driven; deck equipment included twelve cargo winches, steam cylinder sizes 7 inches by 

 10 inches: 



Usual engine-room auxiliaries operating twenty-four hours and an average of ten 

 cargo winches operating from eight to nine hours. Average fuel consumption 

 per day, tons 11 



Usual engine-room auxiliaries in operation twenty-four hours, no cargo winches or 



other deck auxiliaries operating. Average fuel consumption per day, tons .... 4 



One cargo winch in operation for five hours continuously handling 1,000 pounds 

 sling loads of cargo from hold of ship to dock. Average steam consumption per 

 hour, lbs 1,200 



