ELECTRIC PROPULSION OF MERCHANT SHIPS. 285 



cates of electric drive, I notice that electrical engineers are very careful to keep water away 

 from generators in stationary plants as well as those on board ships. 



I might mention an experience on a trial trip of a certain gea red-turbine vessel. This 

 trial took place in a gale, the wind at the time blowing as hard as 80 miles an hour, the seas 

 so high that solid water was taken over the forecastle when the ship was running on a 

 course with the wind about four points abaft of beam. There was also a very hard rain, 

 but it was necessary to keep the engine-room skylight open on, account of ventilation. The 

 spray and rain came through the open skylight and landed on top of the gear case. If this 

 had been a piece of electric machinery, generating current at high voltage, the result would 

 probably have been short circuits. It would also have been a source of danger, not only to 

 the machinery, but to the engine-room crew as well. Troubles were experienced with the elec- 

 tric circuits on this trip. 



Serious troubles with geared-turbine outfits have been caused by the following reasons : 

 First, improper design; second, poor material; third, poor workmanship; fourth, gears 

 too small for the power transmitted through them; fifth, poor foundation; and sixth, poor 

 operation. 



The following statement is made: — "In fact, there seems to be no type of gear with 

 which trouble has not been experienced after long senace, in cargo vessels." This state- 

 ment is only correct in one sense, depending on what is meant by trouble. There is no 

 machinery built for marine or stationary work that has not given some trouble at one 

 time or another. Besides, this statement is not consistent with what is said above in the 

 same paragraph, v^'here it is stated : — "In some merchant ships gears have been, very suc- 

 cessful, etc." It is also stated that gears for ships have "not yet reached a state of fin- 

 ished development," but what assurance have we that the electric propulsion equipment 

 has reached this finished state. 



The question raised regarding damage that would occur to operating turbines in the 

 reverse direction seems to be more theoretical than real. With large direct-drive turbines 

 few accidents have occurred; with a small turbine such as is used in the gear drive these 

 accidents would even be less. This is borne out by practice. 



It is stated that the efficiency of generator is 95.6 and the motor 95.9, making a trans- 

 mission efficiency of 91.6, including cable losses. If this be true, the cable losses must be 

 , zero. 



Reference is made toi loss due to friction of the line shaft bearings which the electric 

 drive would not have as the motor is placed in the stern. The shaft in this case is very 

 short. Experience has been that the stern bearing wears down very rapidly, causing the 

 propeller shaft tO' come out of line with the line shaft. This is largely taken care of by 

 the flexibility of the shaft, which does not exist when the motor is placed in the stern. In 

 almost all cases of general cargo ships it is considered desirable to place the machinery 

 amidship, in spite of the space lost by the shaft valley. 



I understand from Mr. Smith that the electric drive was more expensive than either 

 the gear turbines or reciprocating engine, as well as being heavier and requiring more 

 space. 



The slight disadvantage, as mentioned, of using a propeller turning 100 revolutions 

 would only exist under favorable conditions. In rough weather or with a foul bottom 

 these disadvantages would increase. 



Regarding the operating forces it is stated : — "Conductor circuits are much simpler 



