[PORT FIRES AND SHELL FUSES.]
These are unchoked cases, like roman candles; 6 inches long, 3⁄8 internal, 41⁄2/8 external, is a good size. They should be rammed, as hard as possible; and, for this purpose, it is best to have a mould. Now, if a case is rolled of such a size that it will exactly fit into a brass tube, and is charged, in it, very hard, it will swell, and it will be almost impossible to get it out again; but if it be made a trifle smaller, so as to just slip through the tube; then, if a piece of writing paper be rolled, dry, round it, once or twice, so as to make it a tight fit, and the case is charged, it can be pushed out, like a pellet from a popgun, leaving the writing paper, generally, in the tube, or mould, and the case will come out without a wrinkle.
Let the composition be put in, very little at a time, and well driven with a solid rammer and mallet. Fig. 59 represents the mould; the foot b fits the tube a; the tenon c fits the case; a wire, d, goes through 2 holes in the brass tube, and a hole through the foot; a nut, e, to keep the wire from jarring out, is made of a piece of indiarubber: make a hole through it, with a bradawl, and slip it on the wire; or, a screw-eye may be passed through and held with a leaden, or wooden nut.
TOURBILLIONS.[A]
A tourbillion, so called from the French word for whirlwind, is a case made to rotate and ascend at the same time, forming a spiral of fire, and ending in the shape of an umbrella.
To Make a Tourbillion.
Roll the case like a roman candle case, but gauge it to the thickness of a rocket case. Let the inner diameter be 6⁄8; the outer 9⁄8; the length of the case 71⁄4 inches, fig. 43. To charge the case, have a mould, as directed for port-fires; and let the tenon rise exactly 3⁄8 of an inch up the case. Put in a little composition at a time, and mallet it as firmly as possible, till within exactly 3⁄8 of an inch of the top of the case; so that there will be a vacancy of 3⁄8 of an inch, at each end. Fill each of these ends flush with plaster of paris. It is, better, too, if you can manage to fill the middle half-inch of the case with plaster of paris. It can be effected with care, and will hold the screw, hereafter to be described, more firmly.
Construct a wooden box, fig. 44, consisting of a bottom and two sides only, firmly screwed together. Each of the pieces of wood is to be 71⁄4 inches long, and 1⁄2 an inch thick. The internal breadth of the box is to be exactly 9⁄8 of an inch; and its internal depth exactly 41⁄2/8 or 9⁄16, so that when the tourbillion is laid evenly in it, and pressed down to the bottom, half of the case will be in it, and half out of it. At a point b, fig. 44, on the top of the side, half an inch from a, make an ink mark: and, at a point d, half an inch from c, make another ink mark. Fig. 45 is the bottom of the box. At a point w, 5⁄8 of an inch from the end; and, at a point z, 5⁄8 of an inch from the other end, make holes with a fine bradawl, truly, in a line down the middle of the wood, as between side and side. The distance w z is 6 inches; divide it into 3 equal parts, in the points x and y, two inches asunder. Bisect x y in the point s. Procure 5 carpet pins, fig. 47: they will, probably, be 3⁄4 of an inch long. Drive them through the holes w, x, s, y, z, inverting the box for the purpose, so that they shall stand bolt upright in the box. Now screw, or nail a piece of wood over the bottom of the box, entirely to cover it, to prevent the carpet pins from getting displaced. It will be seen, that, if the tourbillion be now laid evenly in the box, and pressed down till it rests on the bottom, the projecting pins will make 5 holes, in the under part of the case. While it is thus lying, with a stiletto, such as used by sempstresses, for making eyelet holes, prick the side of the case over the line b, of fig. 44; and, also, over the point d. There will now be 7 holes; 5 underneath, 1 to the right, and 1 to the left: the latter are the places for the whirlers, or holes of rotation: 4 underneath, for the lifters, or holes of ascension; the centre one, s, receives a nail or screw. Take a bradawl, fig. 49, 3⁄16 of an inch diameter; and slip over it a shield, consisting of a piece of wood with a central hole up it, like a pop-gun, of such a length, that, when it is slipped on, only 1⁄4 of an inch of the bradawl protrudes; or, instead of a bradawl, fix in a handle, a wire of equal length, namely 1⁄4 of an inch, and file it to a point. Push this into all the holes, except s, making 4 holes underneath, and 2 horizontal holes, one left, one right: all these holes will be exactly of the same depth, on account of the shield: see that they are bored perfectly true, the horizontals exactly 90 degrees above the others, or 1⁄4 of the circumference.