Rocket Heads.

Heads for small rockets may be made of two or three rounds of paper rolled dry, and secured on the inner and outer edges with paste. After sticking it on the case, which it may be made to fit, as in fig. 36, pinch the top in like a choke, only tight, and tie it round with twine or flax. For coloured rocket heads, ⁶⁄₈ and upwards, the head may be enlarged by fixing a collar round the top of the case. To make the collar for a ⁶⁄₈, roll a case on a ⁹⁄₈ former, and when dry cut it into short lengths in the lathe, as recommended for pill-boxes; if unprovided with a lathe, saw it with a fine-toothed saw. The advantage of the enlarged head is, that it brings the stars nearer to the rocket, and prevents it from being top-heavy. Another way is to make the heads tapering, and the tops conical, as in fig. 39. One part is rolled on fig. 34, the other on fig. 35; or, a cone may be made of a circular piece of paper, without a former. Cut the circle, along the radius, to the centre; bend it into a cone; secure the edge with sealing-wax, and paste paper over it to overlap the rim: snip the edge with the scissors; paste it inside, and secure it to the other part. But the quickest way of all is to make a long paper bag, which may be made to fit to the greatest nicety. For this purpose take a tape-measure; or lay down, on the edge of a strip of writing paper, 7 or 8 inches long, and 1 inch broad, 6 inches, divided into eighths, transferred from a foot-rule. Suppose the ⁶⁄₈ rocket has a collar, which, on being measured by the paper just alluded to, is found to be 4²⁄₈ inches round; add to this ³⁄₈ for lapping over, making 4⁵⁄₈ inches. Cut a piece of imperial brown 4⁵⁄₈ broad, and as long as the case, 6 inches. Make this into a paper bag, 2¹⁄₈ inches broad. Be careful that the corners are perfect; a strip of double-crown may be pasted over them. When dry, pinch the mouth open till cylindrical, and merely allow the stars to drop in without forcing them; this will keep the top edge of a wedge shape, fig. 37, and answer the purpose of a cone. If the paper is thin, the bag must be made of two thicknesses; the paper will, then, require to be 9 inches by 6; 4³⁄₈ of this will have to be kept dry, and the other 4⁵⁄₈ pasted.

A head, made in this way, if required to hold gold rains, or serpents, can instantly be reduced to a cylindrical shape, by pushing the rocket-case right up it, to the top; this will cause the corners to stick out, like two horns; press them down, and secure them with sealing-wax. Attach a cone, if desired.

Heads made like figs. 38 and 39 may be of three thicknesses of paper, pasted all over.

Fig. 39 shows the manner of tying on the sticks. No variation must be made in their lengths, and it is not advisable to alter their size. To adapt it to the wood, however, a slight alteration might be permitted. For instance, instead of ³⁄₈ square, it might be 2¹⁄₂/8 by 3¹⁄₂/8, a slight increase one way, compensated by a slight diminution the other. It must, however, on no account, be so increased and diminished, as to approach the shape of a lath, as such stick would vibrate, and cause the rocket to quiver. When the heads are a paper bag of the shape of fig. 37, the stick must be tied on, as indicated by the dotted lines.

If the stick is suited to the rocket, it will, when suspended on the finger almost against the mouth, as at f, fig. 40, lie, not quite horizontal, but slightly sloping downward. The wood should be dry pine, free from knots. The sticks are generally cut with a carpenter's cutting-gauge. If the learner has a lathe he will find a 6-inch circular saw convenient for cutting them.

For amateurs, a ⁶⁄₈ rocket is a good size; large enough, and small enough. If ⁵⁄₈ and ⁴⁄₈ are made, two hollow drifts will be sufficient; for ³⁄₈, one hollow drift. Very small rockets, ²⁄₈, are made for children; they are rammed solid, and a hole is pushed up them with a bradawl.

Rockets in former times, before the present days of competition, were charged in moulds. These were of gun-metal, bored truly cylindrical, furnished with hinges, to open and admit the case; they were then screwed up, and might be charged as hard as possible. Names were given them according to the bore of the mould, that is, the external diameter of the cases; a ⁴⁄₈ was termed an ounce rocket; a ⁵⁄₈, a two ounce; a ⁶⁄₈ a quarter pound; a 7¹⁄₂/8 a half pound; a ⁹⁄₈, a pound; a ¹²⁄₈, a two pound.

These names were determined by the weight of a leaden ball of the same diameter as the bore. Now a sphere of lead, 7¹⁄₂ inches diameter = 90 lbs., or 1440 ounces; consequently one of 15 inches = 720 lbs., similar solids being to each other as the cubes of their like dimensions: the latter sphere being twice the diameter from top to bottom; twice the diameter from left to right; and twice the diameter from front to back; 2 × 2 × 2 = 8.

The external diameter of the rocket being 7¹⁄₂ inches, the internal would be 5 inches, and this would be a 90-pounder: hence, for an inch rocket, we have the proportion,

5³ : 1440oz. :: 1³ : 11·52oz.

so that a 12-ounce, or 3-quarter-pound rocket, ought to be a trifle above an inch.

Required the weight of a ⁶⁄₈ rocket. 5 inches = ⁴⁰⁄₈.

40³ : 1440oz. :: 6³ : 4·86oz.

So that a ⁶⁄₈ is a trifle too large for a quarter-pound.

If, conversely, we require to know the size of a half-pound, or 8-ounce rocket,

1440oz. : 40³ :: 8oz. : 3200/9

and ∛(3200/9) = ∛(9600/27) = (∛9600)/3 = 7·08

So, properly, a half-pounder is a trifle over ⁷⁄₈. The names in use enable the makers to understand each other, but they are not mathematically correct, and are of no utility to an amateur.

The following table shows the true weight of leaden spheres, the dimensions being taken in inches.

Weight.	Diameter.	Weight.	Diameter.	Weight.	Diameter.
1 dram	·264	1 oz.	·664	1 lb.	1·672
2 drams	·332	2 "	·836	1¼ "	1·8
4 "	·418	4 "	1·056	1½ "	1·91
8 "	·528	8 "	1·328	1¾ "	2·02
12 "	·604	12 "	1·52	2 "	2·112

And ²⁄₃ of the above numbers multiplied by 8, give the correct names for rockets in eighths of an inch.

Required the true size of a half-pounder.

(1·328 × 2 × 8)/3 = 7·08.

A trifle above ⁷⁄₈, as before stated.

A cast-iron ball 6 inches in diameter weighs 30lb.

Cast iron is about ⁴⁰⁄₆₃ the weight of lead.

5280 feet = 1 mile; 3280 feet = 1 kilometre.

[WHEEL AND FIXED CASES.]

Wheel cases may be 5⁵⁄₈ inches long. Cut the paper, without waste, into 4 strips, each 29 inches long. Fixed cases may be 7¹⁄₄ inches long: cut the paper the other way of the sheet, into 4 strips, each 22¹⁄₂ inches long. The extra length, for fixed cases, is to allow of their being reported; that is, filled at the end, with an inch, or more, of grain powder, to make a bang like a squib. The cases are to be gauged to the thickness of roman candle cases, but choked like rockets; ⁵⁄₈ internal, and ⁷⁄₈ external, are a good size. Two solid drifts will be required for wheel cases; one 5¹⁄₂ inches long, besides the head; the other 3 inches: for the fixed cases it will be necessary to have one of 7¹⁄₄ inches. They may be turned of box, beech, or ash; but gun-metal drifts are best, though by no means indispensable. If they are cast in gun-metal, they will simply require filing in the rough places. The cases are to be rammed solid throughout, on a foot, fig. 42, turned in one piece, with a nipple, and a pin ¹⁄₃ of a diameter thick, and just high enough to keep the choke clear.

In all wheel and fixed cases, whatever the remainder of the fuse may be, begin by putting in one scoop of starting fire; this, when malleted firmly in, should fill about ³⁄₈ of an inch in the case. The subsequent fuse can be selected from the Tables. The choke may be protected with a little clay, before the starting fire, like rockets, if thought desirable: no clay is to be used anywhere else. Wheel cases containing steel-filings are termed brilliant.

To prime the cases, very slightly damp some meal powder, by sprinkling it with a few drops of water; mix and chop it up, or mince it, as it were, with a knife: put a little into the mouth of the case, press the nipple, fig. 42, into it, and work it round; this will prime the choke and the mouth at once, still leaving the choke clear; or, paint the choke and mouth with the sash-tool, with meal paste, just sufficient to wet them, then plunge them into dry meal, give them a rap to shake off the superfluous dust, and lay them by to dry.

Wheel and fixed cases need not be choked at all, but plugged ¹⁄₄ of an inch, with plaster of paris, as directed for roman candles. When dry, charge them by setting them flat on the block, without using the foot. Mallet in a scoop of starting fire, then the other. Afterwards, when a number are charged, bore through the centre of the plaster, with a shell-bit, ¹⁄₃ the diameter of the case; insert a piece of match in the hole; wash the face of the plaster over with meal paste, and plunge into dry meal. A sheet of double-crown makes 8 wheel case envelopes (2.2.2) 10 by 7¹⁄₂, so that the void at each end, to receive the match, is nearly 1 inch.

It is not possible to devise a formula that will indicate the exact quantity required for wheel cases, as the fuses vary; but, representing the length, in inches, by I; and the diameter in eighths by e, the following will help to serve as a guide.

(I e²)/7 = drams.

Suppose a wheel case 5⁵⁄₈ inches long, and 4 eighths diameter,

(5⁵⁄₈ × 4 × 4)/7 = ⁹⁰⁄₇ = 13 drams.

Suppose a fixed case 7¹⁄₄ inches long, and 5 eighths diameter,

(7¹⁄₄ × 5 × 5)/7 = ¹⁸¹⁄₇ = 26 drms. = 1 oz. 10 drms.

[GERBES.]

Gerbes, so called from the French word for wheat-sheaf, which they resemble, are fixed choked cases: they do not show well on wheels. As they contain grains of iron, they must not be under ⁶⁄₈; for private exhibitions a good size is ⁹⁄₈, ⁹⁄₈ internal diameter; ¹²⁄₈ external; ³⁄₈ the diameter of the choke; 11¹⁄₄ inches, length of case. Charge the case on a nipple, exactly like a wheel case. It is advisable to put in, first, a little clay, to protect the choke, as the fire, being fierce, would, otherwise, enlarge it, and diminish the ascent of the sparks. Upon the clay drive in a scoop of starting fire, and fill up with gerbe composition. This, when containing iron borings, is termed Chinese fire; the pieces, Chinese trees.

The most magnificent of all, however, is the coloured gerbe. For this, some green, blue, and crimson grains, or small stars must be prepared. They may be quarter-inch cubes, cut as directed for the chopped nitre stars. A far better way, however, of preparing them, is to remove the pin a, of fig. 2, up to c, so that the stars, driven in the tube, will be ⁵⁄₈ inch diameter, and ³⁄₈ thick. When these are dry, chop them into 4 pieces, by holding a knife, or chisel, across them, and giving it a smart blow with the mallet. They are harder made this way.

To charge the cases: having driven in the clay, and the starting fire, put in 7 or 8 stars, then a scoopful of fuse No. 1 or 2, then 7 or 8 more stars, and another scoop of fuse; mallet the whole 4 layers down firm, with blows not too heavy at a time, but many times repeated. Then put in 7 or 8 more stars, another scoopful, 7 or 8 more stars, and another scoop, and mallet the 4 layers as before; and so repeat. The two layers and the two scoopfuls may fill up, when malleted in, ³⁄₄ of an inch, in a ⁹⁄₈ case.

Instead of choking the cases, plaster of paris is far preferable. Let it be ³⁄₈ of an inch thick, and well dried, before charging. After the cases are charged, bore a hole through the plaster, ¹⁄₃ of a diameter, that is, with a ⁹⁄₈ case, ³⁄₈ of an inch diameter. For this purpose it is not necessary to have another shell-bit; bore it with the ³⁄₁₆, and enlarge it with a penknife. It is better arched under, till conical, as shown in fig. 48. Prime with 4 or 5 pieces of match, and wash with the sash-tool.

The gerbe being finished, make a cylindrical box, or paper bag, of 2 or 3 thicknesses of paper: fill it with a number of crackers, and a scoopful of meal powder, and fasten it to the gerbe.

No single piece is more effective than a coloured gerbe; the stars will be projected 30 feet, or more: they may be put in, mixed; or, one layer may be blue, another green, another crimson. Twist a piece of wire, deprived of its elasticity, round the neck, and another piece round the bottom, and leave long ends; it can then be fastened by them to the top of a post. To remove the elasticity from iron wire, lay it in the fire till red hot; withdraw it with the tongs, and put it aside, to cool slowly. If copper wire is used, it will bend without preparation. String must not be employed, as it might burn, and let the case fall. Common pins, patent short whites, deprived of their elasticity, are useful for connecting the parts of lustres together.

[FLOWER POTS.]

These are choked cases, charged with spur fire: the fire is somewhat slow, so the cases must be short: 4 inches long, and ⁵⁄₈ diameter is a good size. Rub the composition thoroughly up in the mortar; the vegetable black produces beautiful star-like sparks, totally dissimilar to any other. Put a little composition, at a time, into the case, and jolt it with the roman candle rammer.

Vegetable black, introduced into a star, causes it to tail, like linseed oil. Light such star on the hob; it will burn, and leave a residue, unaltered in shape; blow upon this continuously with the mouth, or, better still, with a pair of bellows: the supply of oxygen will cause it to boil up, in a state of fusion, when it will begin to throw out clusters of the peculiar starlike sparks, before mentioned, bright and yellow as new sovereigns.

Vegetable black is a pure lamp black; some samples of lamp black make equally good stars, but others are worthless. Greater reliance can be placed upon vegetable black. Vegetable black and lamp black must not be mixed with linseed oil, as such mixture is liable to spontaneous combustion.

Roll up a tube for pill boxes, of two thicknesses of brown paper. When dry, cut it into pieces about 1¹⁄₈ inch long: choke one end, like a wheel case; set it on a nipple,and charge it with spur fire, till full within ¹⁄₁₆ of an inch: fill up flush with a little plaster of paris, pressed in flat with a knife: prime the choked end, and put a number of such cases into a rocket head, or shell.

[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.