FOR AUXILIARY PURPOSES ON BOARD SHIP. 165 



APPENDIX. 



Further tests than those referred to in the text of the paper were carried out, 

 both by a modified box method and an actual shipboard test on the U. S. torpedo- 

 boat destroyer Terry, to ehminate the uncertainty of the previous box-method tests. 



Mr. Schmidt's criticisms of the original tests (see Journal A. S. N. E., Vol. 

 XXV, No. I ) were quite beside the point, as these tests were purely comparative, 

 and as clearly stated in the report of these tests no attempt was made in view of 

 the apparatus available to determine the actual delivery of the fans. 



In the test carried out on board the U. S. torpedo-boat destroyer Terry, the 

 following method was employed. Air was measured on entering the fans, as the 

 fire-room leakage prohibited any other means of accurately measuring the air. The 

 inlet duct was increased to 12 feet above the normal inlet to the fan and was 41 

 inches in diameter. In this inlet tube a standard Taylor pitot tube was located as 

 shown. This tube was so arranged on a slide that readings could be taken at 

 all points across the diameter. A manometer inclined at an angle of 15° giving a 

 ratio of .2588 to i was used in measuring the ingoing air. 



Static pressure in the fire-room was measured by a vertical manometer of the 

 usual type located in the fire-room, one end being connected to the outside atmos- 

 phere. Temperatures were also recorded. 



The readings of the first tests were very unsteady. Adjustments made in the 

 pitot-tube openings were without result. A slight wind varying in velocity and di- 

 rection disturbed the readings. In the next test the pitot tube was secured by wire 

 stays to prevent vibration, but no improvement was noticed. 



Plate 86 shows the irregularity of the readings taken, these readings being 

 taken by moving the pitot tube to various positions across the diameter. Aver- 

 aging up the results of these tests will give a velocity of 2,279 f^^t per minute, air 

 temperature of 79° P., density .073, area of inlet tube 9.17 square feet, correspond- 

 ing delivery 20,900 cubic feet per minute at constant 5-inch static pressure. 



Further tests were made by lowering the pitot tube to position B shown in 

 Plate 87 (Exp. 1) ; also various devices were employed for preventing the tube from 

 vibrating. 



Directly adjacent to the walls of the tube the manometer would steady itself. 

 It was therefore considered that the inductive windage over the duct of the inlet 

 tube was interfering considerably with the accuracy of the tests. 



A hood was next fitted, as shown in Plate 87 (Exp. 2), to increase air ve- 

 locity, minimize wind efifect and prevent eddy formation. Tabulation of the tests 

 follows : — 



