PERIOD OF VIBRATION OF STEAM VESSELS. 137 



riences within the last few months where two of our steamers, of exactly the same size and 

 the same engine power in each case, have broken off three propeller blades. They are single- 

 screw, four blades to the screw. In the case of the first one they started up the engine and 

 the vibration was so great that they worked the engine slowly and went back to port, about 

 fifteen or twenty miles. They lay there until they got a diver to take off the balance of the 

 blades and replace them with new ones, all of the blades being replaced. 



In the other case the boat was just leaving Escanaba and had not got out of the har- 

 bor, when three blades broke off at once. Instead of stopping there they went on. The 

 captain and the engineer decided that they could get along with one blade, which they did, 

 and made almost as good time as they would have done with the four blades. (Applause.) 

 The boat runs at about eleven miles an hour, as a rule, and they averaged better than nine 

 miles an hour all the way down, average run. After they got going, and after the boat got 

 some headway, there was very little vibration with one blade. The boat ran very steadily so 

 that even in shallow water — in crossing Lake St. Clair, where the water is very shallow — she 

 did not vibrate at all. I presume the depth of water had something to do with it. When she 

 first struck Lake Erie, with the water a little deeper, but not very deep, she did vibrate, and 

 they slowed her up for about fifteen miles, and then opened her up and went ahead full 

 speed, turning up faster than the usual turning. I thought the matter might be of interest. 



Mr. Elmer A. Sperry, Member: — That reminds me of the early history of the screw 

 propellers. The screw went clear around the hub, and it was found, the more parts of this 

 screw that were knocked off the propeller the better it became and the more speed could be 

 made; but even though there was not much vibration experienced with the one screw imder 

 the conditions named, yet it practically left lagging pitch in the single blade, and that would 

 give vibration. 



When the Lusitania was on her trial trip her stern shook so as to be uninhabitable. That 

 was true to such an extent that one would think that the stem rose and fell a foot. Of course 

 the Lusitania was the proudest ship of England at the time, and England's great men were 

 aboard on the trial trip in their dress suits each evening. When this vibration became 

 apparent Sir William White used every possible means to get in touch with the great Dr. 

 Schlick, of Hamburg, to come to the Lusitania with his pallograph and see if he could trace 

 the source of the vibration. Dr. Schlick came, and I saw the doctor afterwards. He said it 

 was the hardest work he ever did in his life. He had to appear at night in his dress suit. 

 In a day and a half he had traced the vibration to one of the three propeller shafts. He 

 had made a scratch line on the inside of the boat on one of the propeller shafts, and opposite 

 that line, he told them, there was one wing of the three-bladed propeller that had two degrees 

 leading pitch, and the vibration was due to this blade. They got the ship into the drydock 

 and pumped it down so that they could expose that particular blade, then they put battens 

 on, and the best they could determine was 1.8 degrees leading pitch, just as Dr. Schlick 

 had said. They chipped it, and got it back into pitch equal to the other blades. At noon the 

 next day they tested the ship again, and found that the vibration had totally disappeared. 

 Sir William White told me that Dr. Schlick could have had anything in England after this 

 achievement. 



The Chairman : — Are there any further remarks on this paper, gentlemen ? The fur- 

 ther it goes, the better it gets. If there is no more discussion, we will call on Mr. Gate- 

 wood to make such reply as he desires. 



