228 



P Y R O T E C H N Y. 



Pyrotecb. 

 ny. 



PLATE 

 CCCCLXXII 

 Fig. 2. 



Fig. 1. 



may be fitted, and about an inch or more in depth, is 

 made in it, so that, when applied, they may both form 

 a solid piece as it were, taking care that the meeting 

 is quite perfect below, and that the upper cylinder 

 stands perpendicular and firm. 



It is usual now to have two of these bottoms to each 

 upper cylinder, one of them bearing both a nipple a, and 

 a spindle b, and the other a nipple a, alone. The latter 

 is required for receiving the rocket when the clay wad- 

 ding is driven down ; and it is also convenient for fill- 

 ing the class of cases that do not require boring. The 

 spindle is of course required for all works which, as 

 well as rockets, are to have a cavity. But one bottom 

 may 6erve for both purposes without difficulty. For 

 this end, a hole is to be bored in the lower cylinder, 

 yet not quite through it, exactly corresponding with 

 that one in the upper piece of the mould. To this 

 must be fitted two metallic cylinders, one with a hemi- 

 spherical nipple turned on the end, the diameter of 

 which is less than that of the whole bore, and equal to 

 that of the case. The other carries the spindle, which 

 may either be turned in one piece with it, or fitted 

 into the nipple, and then firmly secured. It is so es- 

 sential that the spindle should be precisely in the line 

 of the rocket's axis, that too much care cannot be taken 

 in making it true and firm, that it may be liable to 

 no accidents. 



The diameter of the spindle at the base, as we al- 

 ready noticed for the bores of rockets, is half the inte- 

 rior diameter of the case, and is to be fitted exactly to 

 the choke or vent. This is done, by using a wire of 

 the same dimensions in the subsidiary piece of \he for- 

 mer t which we ought to have noticed before, and 

 which is inserted into a hole in it, to be used when the 

 case is choked. The length for rockets is within a di- 

 ameter and a half, or nearly, of that of the composition ; 

 but it is more particularly detailed in our tables of 

 rockets. For wheels the diameters of the spindles are 

 the same, but the length need not exceed one or two 

 diameters of the composition, according to the initial 

 velocity which the artist wishes to communicate. Last- 

 ly, to keep all these parts firm and steady, a hole must 

 be bored horizontally through the lower cylinder and 

 upper, including the piece which carries the nipple. 

 To this a wire, a b, furnished with a ring, a, for with- 

 drawing it, is fitted, which being passed through, and 

 secured on the further side with a forelock if necessary, 

 the mould is ready for use. 



In all the smaller works, or even up to two inch di- 

 ameters, the upper cylinder may thus be made in one 

 piece with a bore. But when port- fires are to be dri- 

 ven, the length of the cases is such as to render it dif- 

 ficult to introduce them, and nearly impossible to with- 

 draw them, in consequence of their extension within 

 the mould. Such moulds, therefore, are best made of 

 two half cylinders well fitted, and held together by 

 driving two or three metal hoops on them. The out- 

 sides should be somewhat conical, to admit of their be- 

 ing the more easily taken off when the case is removed, 

 by separating the two parts of the mould. Moulds like 

 these are best made of metal, and as they require nei- 

 ther nipples nor spindles, being burnt without a choke 

 at the ends at which they are driven, they may be al- 

 together sunk within a hole of the block fitted to re- 

 ceive and retain them firmly. Other cases that burn 

 without chokes, such as illumination lights, small ser 

 pents, &c. may be treated in the same manner. 



Similar divisible moulds are also most convenient for 

 large rockets in cases of whatever nature, as they are 



Pyrotcch- 

 nv. 



both most easy to fit and to remove. These may be 

 made of wood, and secured from splitting by hoops 

 and gun metal in the same manner. Y ^" > ' 



It is not now necessary to be particular with respect 

 to the simpler moulds, since the principles applied to 

 those of port-fires are nearly applicable to all. In the 

 smaller cases, such as serpents, the bores may be made 

 for many different sizes in one block of wood ; and if 

 many bores of the same size also are made, much time 

 will be saved. These bores, which constitute the 

 moulds for such cases, must pass quite through the 

 block, as the case cannot be withdrawn as it entered, 

 but must be driven through. A mould thus made re- 

 quires only to be placed on the block, to which it may 

 be securely fastened by two loops and pins, as well at 

 in many other ways that are too obvious to require de- 

 scription. 



On the making of Cases. 



This is an important branch of the general matters On the 

 which concern all fireworks alike. We shall have oc- mal ng of 

 casion to mention the sizes and proportions of these for cases * 

 different kinds of fireworks when those are described ; 

 but, in the mean time, the same general principles be- 

 ing applicable to all, they will with more brevity be 

 all condensed nnder this general head. 



Materials for Cases. 



Paper, wood, and metal are the only materials appli- Materials 

 cable to the making of cases, and the uses of the two for cases, 

 latter are so very limited that a few words will suffice 

 respecting them, For throwing paper shells a metallic 

 mortar is to be. preferred, at least in the hands of those 

 artists who are frequently called on for exhibitions, as 

 they are steady, and last for ever. They need not be 

 very strong, as the change of powder which they carry 

 is commonly trifling, and they may be fixed in their 

 beds in a position about two or three degrees off the 

 perpendicular, to permit the shell to fall out of the way 

 of the spectators. A common square box of stout elm, 

 well dove-tailed and nailed, serve the same purpose for 

 discharges of serpents and stars. We shall have occa- 

 sion to speak of iron cases for rockets under the di- 

 vision of military fireworks. 



For paper cases, three or four sorts at least are want- 

 ed. For the spiral wheels it is necessary not only that 

 the cases should be flexible, but that they should burn 

 with the composition, as the wheel would otherwise 

 burst and fly off from the support. The paper for 

 these is such as is used for musket cartridges; this 

 being made of new hempen materials, so as to be 

 very strong and tough. If made with the common 

 gray paper of the shops they are apt to burst in at- 

 tempting to give them the spiral form. A thicker kind 

 of gray paper is required for illumination cases which 

 are of a small size, as well as for all the inferior sizes 

 of fireworks of whatever description. This is com- 

 monly termed cartridge paper, being used for cartridges 

 for small ordnance. For the larger sizes of fireworks 

 a harder and thicker quality is necessary ; and if larger 

 rockets are to be made, the artist should only use 

 what is properly called rocket paper, which is still 

 thicker, and is condensed by rolling in the mill, in 

 the manner of pasteboard. For the very largest sizes 

 of all, pasteboard itself is preferable, as there is much 

 time saved in the making, and as the work is much 

 firmer. 



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