ON THE STRENGTH OF LOCOMOTIVE BOILERS. 53 



Experimental Researches to determine the Strength of Locomotive 

 Boilers, and the Causes which lead to Explosion. By William 

 Fairbairn, F.R.S. 



[A communication ordered to be printed among the Reports.] 



A DIFFERENCE of opinion having arisen between a gentleman high in 

 authority and myself concerning the causes of an accident which took place 

 through the explosion of a locomotive engine at Manchester, on the Eastern 

 Division of the London and North- Western Railway, I deemed it necessary 

 to institute a series of experiments, not for the purpose of confuting the ar- 

 guments of others or confirming my own, but to determine the real causes 

 of the explosion, and to register the observed facts for our future guidance 

 in guarding against such fearful catastrophes. 



After a careful examination of the boiler a few hours subsequent to the 

 explosion, I found one side of the fire-box completely severed from the body 

 of the boiler, the interior copper box forced inwards upon the furnace ; and 

 with the exception of the cylindrical shell which covers the tubes, the whole 

 of the engine was a complete wreck, as exhibited in Plate I. fig. I. 



Mr. Ramsbottom, the Locomotive Superintendent, in his Report to the 

 Directors, states that " the engine in question was made l)y Messrs. Sharp, 

 Roberts and Co. in the year 1840, has been worked at a pressure of 60 lbs. 

 per square inch, and has run in all a distance of 104,723 miles, a great part 

 of which has been either entirely without load, or nearly so. As the cylin- 

 ders are only 13 inch diameter, it has been for some time too light to work 

 any of our trains; and ha^s therefore been chiefly employed since 1849 in 

 piloting the trains through Standedge tunnel, along with another engine of 

 the same size, which is now at work. 



" The fire-box was originally ^^ths of an inch thick, and is now a little over 

 -^ths of an inch ; and from its excellent condition, might well be supposed (as 

 indeed it was by Mr. Sharp, of the firm of Sharp Brothers and Co., who 

 inspected it a few days after the accident) to have been recently put in new. 

 It is perfectly free from flaw or patch, and would certainly have run at least 

 100,000 miles. The same may also be said with respect to the outer shell, 

 which is nearly of the original thickness. The engine had been in the 

 repairing shop the three months previous to the accident; and the iron fire- 

 box stays, about which so much has been said, were tested by the hammer 

 in the usual way, and were considered, both by the workmen and the foreman, 

 Wheatley, to be all sound. When originally made, they were y^ths in 

 diameter, and were equal to a strain of at least ten times the force they had 

 to sustain. With the exception of one stay, which was on the top row, the 

 one most reduced from oxidation was half-inch diameter; and supposing the 

 hold on the copper box to have been good, it was capable of resisting a strain 

 of rather more than 6^ times the working pressure, equal, say, to 390 lbs. 

 per square inch. The only point therefore which could admit of doubt as 

 to the safety of the boiler, was with respect to the hold which the stays 

 might have in the copper box ; but it appears, from experiments which I 

 have since made, and which are about to be repeated by Mr. Fairbairn, that 

 from the force required to pull some of the old stays out of a copper plate 

 similar to the fire-box, into which they had been screwed by the old threads 

 only, and not riveted, the boiler could not have burst under a pressure of 

 less than 300 lbs. per square inch. One of the old stays, which had had the 

 thread partially damaged from being ripped out of the copper box by the 

 explosion, was screwed by hand into a copper plate, by the old thread, to a 



