STRAINS IN THE HULL OF A SHIP AT SEA, AND THOSE 

 MEASURED WHILE RECEIVING CARGO. 



By James E. Howakd, Engineer-Physicist, Bureau of Standards. 



[Read at the twenty-first general meeting of the Society of Naval Architects and Marine Engineers, held in 



New York, December 11 and 12, 1913.] 



Strain gauge measurements were made on the plates of the shelter deck of the 

 S. S. Ancon, of the Pacific Railroad Steamship Company, on a voyage from New 

 York to Colon and return, and subsequently during the time the ship was taking 

 cargo aboard at New York. 



The Ancon, originally called the Shawmut, was built by the Maryland Steel 

 Company, Sparrow's Point, Md., in 1902. It has the following dimensions : Length, 

 505 feet; beam, 58 feet; depth, 41 feet; di placement at 30 feet draught, 20,830 tons. 



It has twin screws and is equipped with triple expansion engines of 24-inch, 

 39^ -inch, and 62-inch diameter, 45 inches stroke, making 78 revolutions per 

 minute. Steam pressure carried, 200 pounds. 



The ship makes about 12 knots per hour. 



For a time the ship was used in the China trade, but of late in the transporta- 

 tion of structural materials for the Panama Canal, of which cement usually formed 

 the principal part of the cargo. 



Live load strain measurements were made on the deck plating while the ship 

 was at sea, using a new type of extensometer designed by the writer, a scissors 

 gauge, so called from the resemblance of its working parts to a pair of scissors. 

 Figure i, Plate 65, is an illustration of this gauge, nearly full size. 



It consists of two beams, which, taken together, are rectangular in outline, 

 and between which are located two small bell crank levers. Parallel motion of the 

 beams is secured by the use of flexible stay plates. The bell crank levers are 

 mounted upon fulcrums made of thin plates of tempered steel. They work in op- 

 posite directions. The long arms of the levers are blades which make with each 

 other a small angle, the vertex of which or point of intersection of the blades mark- 

 ing the place where the reading of the instrument is taken. 



The blades are comparatively light ; the beams are relatively heavy. The in- 

 strument is dust proof. The proportions of the parts are such that a change in the 

 position of the point of intersection of the blades of one inch in length represents 

 a movement of the beams, or measured movement of one-thousandth of an inch. 

 The index plate is graduated into ten parts, each representing one ten-thousandth 

 of an inch. A change in position of the point of intersection of .01 inch on the scale 

 represents one one-hundred-thousandth of an inch movement of the beams. The 

 gauge has a total range of movement or full scale reading of one-thousandth of an 

 inch. 



