254 



MAJOR J. H. MANSELL: INVESTIGATION OF 



Now the first results of this calculation are not at all obvious. But by adjusting 

 the zero of the curve calculated on the cord law and comparing it with the actual 

 record it seemed possible that at some point, to be determined, excess internal 

 pressure disappeared and the tubes then burnt in strict accordance with the law in 

 Table B. In adjusting the calculated curve so that its general lie was in closest 

 agreement with the measured one, I found they crossed at about 57 tons. It then 

 seemed that if internal excess pressure disappears at any point it must start at some 

 maximum. A simple way of considering the decrease of excess internal pressure 

 from a maximum to zero is to consider that the internal pressure in the tube is 



Ton a/in* 

 20 



19- 



tfl 



Double 



tubular M.O. t 80 I 



A- -2 3 



17- 



Poi 



lt A3 



measured off 



!6 the"_recor J-. 



o Points ca cul&ted by 

 15 - table C. 



Tub: M.D. 



at 80 



F. A. 



Batth 97 



ft - 0-25037 



- 0-090O3 



II - 



10- 



7 



9- 



8 



7- 

 6 



.7 



5- 

 4 



002 



004 



006 -008 



OIO 



014 



OI6 -OI8 



Time- Seconds 



020 



022 



024 



026 



028 



030 



09 -034 



Fig. 7. Time rise of pressure. 



a constant until the pressure in the vessel reaches that given pressure. From that 

 moment internal and external pressures will be equal. 



Referring to the tabulated results of total internal pressure, it will be seen that the 

 average of the pressures given is 4 '56 tons. This was the first pressure tried, but a 

 better result was given assuming 4 '8 5 tons. 



The calculation, then, was made on the assumption that the internal pressure was 

 4 - 85 tons up to the moment at which the pressure in the vessel reached that figure. 

 The external and internal diameters of the tubes at that moment are given by the 

 calculation which then proceeds on the assumption that the internal and external 

 pressures are equal. 



