62 ON THE CONSTRUCTION OF HOOPED CANNON. 



about 25 or 26 inches' diameter, and between proper dies, setts, or swages, it 

 is to be completely welded, or the several layers or coils are to be made to 

 form one piece. This may be done by compressing it with the swages, by a hy- 

 drostatic press, or by a steam hammer. After it is properly welded and 

 condensed in this way, and has cooled as low as 600°, it is to be placed 

 upon a cold arbor, or mandrel (shown, in section, at A, A, Figures 6 and 

 which is supported at both its ends by the upright studs of the heavy iron 

 frame B, B. It is then to be hammered by the steam hammer O, until its 

 internal diameter is enlarged to about 27 inches. The last part of the ham- 

 mering is to be performed after the hoop has become cold. Instead of operating 

 in this way with the steam hammer, we may produce the same effect upon the 

 hoop by a rolling-mill, in which the operating part of the rollers is made to 

 project beyond the housings, or frame. 



After the hoop has been condensed and stretched in this way, it is next 

 to be placed upon an annular anvil, D, D (Figures 8 and 9), and the segmental 

 swages or blocks, E, E, are to be adjusted within it. These segments form a 

 cylinder upon their outer surface, but inside they form a hollow cone. A solid 

 conical plug, F, is fitted to be driven into this hollow cone within the swages. 

 With this arrangement, the whole being under the drop or steam hammer C, the 

 plug is driven by repeated blows into the hollow cone, by which operation the 

 hoop is stretched sufficiently to destroy all conflicting strains or tensions that 

 might have been produced in it by the hammering. The strain is thus reduced 

 to a circumferential direction, and the hoop put as near as possible into the 

 condition of the hard wire (as shown in Figure 2), after it had been subjected 

 to the first series of strains (as shown in Figure 



he hoop may be stretched by this last operation the rh Q k part of its 



diameter, and, if lt is made of very goft and tough .^ ^ ^ ^ ^ 

 hammered very hard, muc h more than this quantity. The extent, however, 

 to which this hammering and cold stretching may be carried, must depend upon 



n ir w 1G ! T " nd the heating and WOrkin S t0 Which it has been 



ET£ y w „ ? WiU ^ WeR ' Wh - * Aching is commenced, to 

 tone the hoop warmed up to 200° or 300°. 



stre^lt ^Tk^ ^^ ^^^ In this ^ *7 cold hammering and 

 Zt^ crew h „ ^ ^ tUrned; ^ Wheth - * * to be fixed to the 

 Lte to I ' 0F 7 "^ eqUiYalent > H is to be —fully and equably 



C« i ^TSt i but never up to an — * ^ - shal1 



ticiently, and, m this state, is to be placed upon the gun. 



In all 



