134 ELECTRIC PROPULSION OP SHIPS. 



We looked into the induction motor, but the lines of the ship were all fine, and she would not 

 carry the weight; and the lines of the appropriation were still finer, and they would not carry 

 the cost, and the synchronous motor was automatically selected. The results we have ob- 

 tained are not at all conclusive so far as fuel consumption is concerned. The results var>' 

 radically. We hope in the course of time to get some reliable information, and that will be 

 published. As a basis of comparison, I will say on this ship we have installed two Babcock 

 and Wilcox boilers built for installation in mine sweepers. The mine-sweeper contracts 

 were cancelled, and the Navy then sold us the boilers for installation in these ships. We put 

 on superheaters, and I believe we used higher air pressure than the Navy intended to be used 

 on the mine sweepers. They were designed to develop 1 ,400 indicated horse-power on triple 

 expansion, which I think is about 1,300 shaft horse-power. The Tampa has developed 2,900 

 shaft horse-power, a good deal more than 100 per cent over the estimated power of the mine 

 sweepers. There is a difference to be expected in the economy of reciprocating and turbo- 

 electric drive, but whether we should take this as a basis of comparison between the recipro- 

 cating engine and the turbo-electric ship, I am not prepared to say. 



Our first requirement in the Coast Guard, I should say, is responsiveness, because the 

 matter of maneuvering is of the first importance. It may not be so with the merchant ship, 

 but we were very much interested to know how quickly we can get a response to a signal 

 from the bridge. It has been found on a number of occasions, with the ship going at 15 

 knots speed, the motor will reverse in eleven seconds from the time the signal is given from 

 the bridge. At that speed the ship can be brought dead in a little more than her own length. 

 In backing and filling the response is instantaneous — you cannot tell when it starts. 



There is one point that Mr. Thau brings out, in connection with synchronous motors, 

 that I do not quite agree with. He says that the synchronous motor is a more complicated 

 mechanism. If you eliminate the ordinary squirrel-cage induction motor, which I have never 

 heard proposed for ship propulsion, the synchronous motor seems to me simpler than any 

 other type of induction motor — that is, a motor in which you have external secondary resist- 

 ance. You have a squirrel-cage winding for maneuvering, and for a full power run you have 

 an ordinary direct-current field, the same, in most respects, as the generator field. Where it 

 differs at all is in the line of being more readily repaired, but the same sort of connections 

 and switches and apparatus in general applies to both the generator and the motor. I believe 

 the synchronous motor to be a simpler machine than the induction motor with external 

 resistance. 



The Tampa, as was announced this morning, is now lying at Pier 59, at the foot of 18th 

 Street, North River, and she will be open all today and tomorrow for inspection, and we 

 hope as many as can will go down and inspect the ship. 



A few words on the control. The handling gear consists of two levers, one being the 

 direction lever and the other the steam lever. A man who can take charge of an installa- 

 tion with ordinary reciprocating engines can go on board and handle this ship without addi- 

 tional instructions. 



The switches are operated on solenoids, but provision is also made for manual opera- 

 tion in case the solenoids are thrown out of operation. It is impossible to perform any oper- 

 ation out of its order. You cannot throw on or off the main circuit when the fields are ex- 

 cited, and you cannot throw on or off the fields if the main circuits are open; and so it is a very 

 safe sort of thing so far as a man's being excited in an emergency and doing the wrong 

 thing — ^you cannot do the wrong thing. 



