ELECTRIC PROPULSION OF SHIPS. 

 Table I. 



133 



1. Number of screws 



2. S. H. P. * 



3. R. P. M— propeller 



4. Fuel consumption, lbs. of oil per S. H. P. 



(all purposes)! 



5. Weight of all engines and boiler-room ma- 



chinery — wet, tons 



6. Weight per S. H. P.— lbs 



7. Cost of machinery 



8. Cost of machinery, $ per S. H. P 



Steam 

 engine 



1 



2,700 

 80 



1.30 



627 

 509 

 1355, 650 

 132.0 



Geared 

 turbine 



1 



2, 600 

 80 



1.08 



449 

 386 

 1319, 000 

 122.5 



Direct-drive 

 Diesel 



2 

 2,600 

 115 



0.45 



786 

 676 

 1625, 700 

 241.0 



Diesel 

 electric 



2 

 2,000 

 120 



0.53 



571 

 671 

 |526, 000 

 263.0 



* Good for 10 per cent more continuously. 



t Represents good average performance; 5.7 per cent can be deducted for high performance. 



Captain O. B. Newman, U. S. Coast Guard, Member: — I wish to speak briefly on 

 one application of the electric drive with which the Coast Guard has recently had, and is 

 now having, some new experience — the turbo- electric synchronous motor drive. The coast- 

 guard cutter Tampa was the first ship in the world for which a synchronous motor was ever 

 proposed. When this type of drive was first suggested to us, and we began to look into it, 

 we found that it appeared doubtful whether the synchronous motor would maneuver under the 

 conditions that are met with in a ship — that is, whether it would start under a heavy load. In 

 order to determine that point we asked the General Electric Company to build an experi- 

 mental set and simulate ship conditions as nearly as they could. They built a 300-kilowatt set, 

 which they coupled to a direct-current generator, and by that means they could put on any 

 load they pleased. This apparatus was subjected to all the tests we could think of, and it 

 maneuvered perfectly. Then we tried to wreck it by doing things wrong, but found it impos- 

 sible to do any damage, and so we decided it was a pretty good motor. We had no way of 

 determining whether, in a seaway with a racing propeller, when the load is suddenly thrown 

 off and suddenly reapplied, the motor might not fall out of step. So far we have not had an 

 opportunity to determine that. The Tampa was built in Oakland, California, at the works of 

 the Union Construction Company, and has made only one cruise, from San Francisco to New 

 York, and the captain says he encountered no bad weather on the voyage to test that. How- 

 ever, we have no apprehension on that subject. 



The Tampa is 240 feet long over all, 39 feet beam, and about 14 feet mean draught, 

 1,640 tons displacement, and has a block coefficient of 0.4765. She has 16 knots speed, and 

 will do better than 2,600 horse-power. 



The chief advantage of the synchronous motor (which Mr. Emmet has already men- 

 tioned) is the matter of accessibility for repairs. By the removal of the pole pieces on the 

 rotor, any part of the motor can be repaired without lifting anything heavier than one single 

 pole piece. I do not anticipate that we shall have to repair the motor, but in case we should 

 have to do so, all parts are easily accessible without lifting any weights. 



The matter of weight was the determining factor in our selection of this type of motor. 



