54 



REPORT — 1853. 



depth equal to the thickness of the fire-box plate, but not riveted, and it 

 required a dead weight of 8204; lbs. to pull it out ; and as each stay has to 

 support a surface of 5 inches, X 5f inches, say 27 square inches only, it fol- 

 lows that a pressure of 820i-r-27= 303*85 lbs. per square inch would have 

 been required to strip it. 



" Another stay, which had not been stripped by the explosion, but M'hich 

 was screwed out of the old box, was similarly treated, and required a force 

 of 9'184 lbs. to strip it, equal to 340 lbs. per square inch," 



Since the experiments here referred to were made, 1 have repeated them 

 with great care ; and taking into account the tensile strength of the stays — 

 in their corroded state — of the side of the fire-box, which to appearance was 

 the first to give way, I find that a force of 380 lbs. upon the square inch 

 would be required to eifect rupture; and the results of the experiments on 

 the resistance of stays screwed into the copper fire-box fully confirm those 

 already made by Mr. Ramsbottom. Assuming therefore that the ends of the 

 screws were riveted, and sound in other respects, we may reasonably con- 

 clude that a strain of not less than 450 to 500 lbs. upon the square inch 

 would be required to strip the screws, or tear the stays themselves asunder. 

 I have founded these facts upon the experiment of the resisting powers of 

 the iron stay screwed into a portion of the copper cut out of the ruptured 

 fire-box, and another experiment of a similar stay first and then riveted, as 

 shown in the annexed sketch. 



The stay marked A, f ths of an inch in diameter, in the first experiment 

 required a force of 18,260 lbs. = 8*l tons to 

 strip the screw, and draw it out of the cop- 

 per; and the stay B, of exactly the same 

 dimensions, but riveted over the end, re- 

 quired a force of 24,140 lbs.= 10'7 tons be- 

 fore it was dislodged*. Taking therefore 

 the mean of those experiments, including 

 those of Mr. Ramsbottom, and we arrive at 

 the results given above, namely, a resisting 

 power of 785 lbs. on the square inch, to burst 

 or produce fracture in the stays and side of 

 the fire-box. 



In locomotive engines of more recent con- 

 struction, where the stays are thicker and 

 formed into squares of 4 to 4| inches, the 

 resisting powers will probably be increased to 

 850 or 900 lbs. on the square inch, that is, 

 7 or 8 times the working pressure. 



On a careful examination of the fire-box 

 and every other part of the boiler, it was 

 found that the stays and copper were perfect, 

 and that they were able to sustain a pressure much exceeding 207 lbs. upon 

 the square inch, as given in the following table. 



In these experiments, the top of the fire-box sank a little, owing to the 

 breakage of a bolt of one of the cross-bars ; but the fire-box stays were quite 

 perfect, and to every appearance would have sustained nearly double that 

 pressure. If the fipe-box stays had been new and the top well-stayed, it is 

 more than probable that a force from 800 to 900 lbs. on the square inch 

 would have been required to cause rupture. 



Vide Experiments in the Appendix. 



