ELECTRIC PROPULSION OF MERCHANT SHIPS. 293 



through a double hehcal reduction gear of the same general type as that used with geared 

 propelling turbines, and that these gears have given just as reliable and efficient service 

 as the motors. 



It has been found, within the last five or six years, that, on account of the dust around 

 the steel mills, it was necessary to wash the air used to cool the turbo-generators, and vari- 

 ous protective measures have been worked out from time to time. The development of con- 

 trol apparatus to the point of being foolproof and efficient has largely been carried out by 

 the steel mills — that is to say, they share the responsibility for the present high state of 

 development. 



Now in the application, of electrical machinery to shipboard use, the U. S. Navy De- 

 partment has done a great deal in connection with auxiliaiy apparatus. They have their 

 standardized specifications, and they have met with wonderfully good results, but, as far 

 as tlie propelling units are concerned, the prol^lem is new. The manufacturers of electrical 

 machinery will have to consult freely with, those engineers who know marine requirements. 

 A case in point is this variation in torque of propellers that Mr. Emmet mentions; while I 

 may be mistaken, I am under the impression that almost all marine engineers have been 

 aware of that variation in torque for a long time and understood it perfectly. 



Among the points that occur to me which must be considered is that a large amount of air 

 will be required to keep the generators and motors cool. That air will have to be taken from 

 outside of the ship, it will vary in the degrees of humidity, and precautions will have to be 

 taken to see that the intalces are thoroughly protected so as not to take in salt spray. 



The mechanical details of the apparatus will have to be given a great deal of attention. 

 As to the electrical details, the manufacturers of electrical machinery have had enough ex- 

 perience, so that I think they will amaze the marine world by the reliability of that end of it, 

 but the bearings must be made so that they can be replaced without employing any trained 

 snakes to crawl around and get at the bolts. That point may seem ridiculous, but an ex- 

 amination of the design proposed to the Shipping Board for installation on twenty-five ves- 

 sels disclosed a condition which would almost indicate such necessity. In such cases, the 

 designer usually states, long operating experience on land engines indicates it will not be 

 necessary tO' replace the bearings. This is not quite convincing. When anything happens to 

 a ship you cannot telephone to construction men to come and replace the broken part or 

 throw a switch on to a central power station to run the motors while the accident is being 

 repaired. However, there is no reason why these problems cannot be worked out satisfac- 

 torily, provided the marine people and manufacturers of electrical machinery get together 

 and swap experiences and go aboard ship and study the operation of this machinery and the 

 results which are to be produced. 



The installation on the U. S. battleship New Mexico is the last electrical installation 

 on a large scale, and some information about the accident which occurred on that ship nat- 

 urally would be interesting because it occurred on a new ship, to which a great deal of prom- 

 inence had been given, and while probably easily explained as having started in a trivial 

 cause, it nevertheless was a serious accident from the financial standpoint ; in a battleship in 

 action it would have been most serious and shows that some elements of reliability have not 

 been taken care of. 



The maneuvering gear, or control apparatus, must be arranged so that, when maneu- 

 vering near docks or near the lee shore, the protective devices which would cut ofif the cur- 

 rent from the motor shall not operate. It is far better to destroy machinery than to de- 



