Part 3
In the next place, when you have made as many cases as you require, the operation of “choking,” or forming their mouth and neck, remains to be done, and is to be accomplished in the following manner:—Procure some strong close string about one-eighth of an inch in diameter; take about one yard of this, and tie one end of it to a ring or nail which has been driven very tightly about 3 feet from the ground into a wall, beam, or tree, and the other end of this string tie firmly round a stout piece of stick or ruler about 18 inches long. Now take the round-ended drift (fig. 4), and insert this into one end of your cases till its rounded end appears about an inch from the other end, leaving, in fact, an inch at one end of the case unoccupied by the drift. Then take the little “choking piece” (fig. 5), and insert its metal point into the hollow end of the drift. This operation is illustrated at fig. 6. Now rub your string well over with yellow soap; the more thoroughly this is done the better. Then pass the stick or ruler between your legs in such a manner that by leaning backwards you can make the string very tight; but before tightening it give the soaped part of the string one turn round the part of the case marked _e e_ (fig. 6), then by leaning backwards you will contract that part of the case until you leave an aperture only large enough to admit the point of the “choking piece.” As soon as this is done tie some string tightly round the neck thus formed, to prevent its becoming larger. The best knot for this purpose is the one given at fig. 7. Then, when you have drawn out your choking piece and drift, the proper name of which latter is “_the setting-down piece_,” your case must be put by to dry thoroughly before use. The apparatus given at fig. 8 is very convenient for choking cases quickly, and is given in case you should think it worth while to make such a thing. Any boy with a fair notion of carpentering would find no difficulty in making it. It is simply a string passed over a small wheel and fastened to a pedal which works on a hinge close to the ground. A glance at the diagram will show you that by putting your foot upon the pedal _f_ the string may be drawn very tight. The case is choked at the point marked F. No choking can be done except while the cases are wet.
[Illustration:
9 ]
Now, supposing that you can do nothing else until your cases are dry, I will, meantime, introduce you to some of your tools. Fig. 9 represents the block and spindle over which your rockets are to be rammed. The case of the rocket is forced, mouth downwards, over this spindle by inserting into it the setting-down piece (fig. 4), which you have used before, and giving the handle of this some blows with the mallet (fig. 10). This operation has the effect of enlarging the choke to its proper size, and of making the mouth of the case very smooth and hard. The diagram (fig. 11), represents the steel spindle and nipple in its proper size. The part marked _g g_ is driven into the wooden block which forms its foot. Fig. 12 represents the rocket-case driven down upon the nipple when ready to be filled with its composition. Figs. 13, 14, 15, are three drifts of different lengths, pierced so as to admit the steel spindle, and to be used for driving the composition into the cases round the spindle. They are used in the following manner:—A ladleful of the composition is put into the case, and then driven down with the longest of these drifts by the mallet; then another ladleful driven with the same. Then a shorter drift is taken for the next few ladlefuls; then the shortest, till the case is full up to the top of the spindle. Then the unpierced drift (fig. 15) is used to ram in some composition solid, and to drive some clay upon the top of this. This operation will be described much more minutely in its proper place. Fig. 17 represents the “former” on which the cases are rolled.
These tools may be procured at a very reasonable price of Mr. Newman, 4, Augustus Street, Regent’s Park, London.
Having made you slightly acquainted with the various tools and apparatus to be used in making and filling rocket-cases, it will now be necessary for me to say a few words about their size and proportion, for much will depend upon accuracy in this particular. I have given you a sketch of four drifts to be used in loading your cases with composition. The longest of these I shall call _the first_; and the shortest, which is the solid one, _the fourth_; this being the order in which you will have to use them. The measurements that I am now about to give have reference only to _the straight part_ of the drifts, not taking their handles into consideration. The length of the first drift is 6 inches; second, 4½; third 3¼; fourth 2¾. The first three of these drifts are pierced or hollow, in order to admit the steel spindle over which the rocket is rammed. The first should be pierced to the length of 4 inches; second, 2½; third 1½.
Taking the exterior diameter of ¼ lb. rocket to be about 1 inch—and this measurement is near enough for our purpose—the former on which the cases are rolled should be ¾ of an inch in diameter, and the drifts about ¼ of an inch in diameter. The “former” should always be slightly larger in diameter than the drifts, because the paper that is rolled upon it is thoroughly wetted with the paste, and in drying will shrink a little; and, therefore, if your drifts be of the same size with your former, you will find considerable difficulty in getting them in and out of your cases; they ought to be a good easy fit. Twelve inches you will find a convenient length for your former.
In case you should wish to prepare rockets of other sizes, and in order that you may readily see the relative magnitude of cases of such sizes as are generally used in the art of pyrotechny, I here append a table:—Those which are called
1-oz. cases are about ½ inch bore. 2-oz. „ „ ⅝ „ ¼ lb. „ „ ¾ „ ½ lb. „ „ 1 „
In following the directions which I gave in my last paper for cutting up your imperial board and 70-lb. brown paper for rocket-cases, you will find that the case produced will not be a very stout one. Although I have made an excellent rocket in a case of such a thickness, you will, perhaps, find it advisable to use more paper and board, and prepare a thicker case. For this purpose cut your board in the manner that I have described before for your 70-lb. brown paper—that is, into _eight_ equal strips—and then cut each of your sheets of brown paper _lengthwise into four_ equal strips. By this plan you will be able to make very stout cases, which will not be at all liable to injury during ramming; and thus one sheet of board, with two of brown paper, will furnish eight ¼ lb. rocket-cases. You must bear in mind when choking them to contract the aperture till it is considerably smaller than you will eventually require it to be. The setting-down piece (fig. 4) has two uses: it is employed first in choking the case, and afterwards in driving or setting it down, when choked, over the steel spindle. The reason for driving the case thus down till the mouth is brought close to the nipple at the foot of the spindle is that the choke or aperture may thus be left of the proper size. This proper size is about two-fifths of the inner diameter of the case; and the aperture left immediately after choking should not be much more than one-fifth of the same inner diameter. The operation of “setting down” the cases is performed best, in my opinion, when they are perfectly dry and immediately before they are filled.
ROCKET COMPOSITION.
5. Now supposing your cases to be thoroughly dry and ready to be charged, the next thing that we must consider is the composition with which they are to be filled. Judging from the effect produced by rockets prepared by different makers, I should imagine that the formulas for their compositions are of almost endless variety. Some seem to prefer a very quick composition, which will raise the rocket to a great elevation in a very short time; others, one which will produce a large and rich tail of sparks not ascending so fast or so high. In my opinion, the mean between these two extremes is decidedly preferable: that which I aim at in rocket manufacture is to produce a very high, but not a very rapid, ascent; and when this my object has been properly gained, I have never had any fault to find with the tail of sparks which is thrown out. I may say, without any exaggeration, that I have experimented upon several hundreds of different compositions, varying first one ingredient and then another, increasing or decreasing them by very gradual steps, until I have come to the conclusion that the two following are the only ones worth retaining. But it must be remembered that it is not enough to have a good formula or two in order to be successful, for much will depend upon _the manner in which_, and _the care with which_, these are made up:—
No. 1. Nitre 16 parts. Sulphur 4 „ Charcoal 8 to 9 „
This, I believe, is a very old formula, and, provided the charcoal be properly prepared, may be found very useful and effective. I used this receipt for a long time, and thought it incapable of improvement, until, from a wish to try the effect of the addition of a little meal-powder, I came by chance upon the following, which I do not think can be surpassed:—
No. 2. Nitre 16 parts. Sulphur 3 „ Meal-powder 4 „ Charcoal 8 „
Now let me tell you that the success of rocket compositions depends upon two things—the intimate union of their ingredients, and the fineness or coarseness of the charcoal. Such charcoal as you can procure at a chemist’s ready pounded will be of no use whatever to you, for it is in far too fine a state of subdivision. You will require a much coarser charcoal for the most part, and one not of the same coarseness or fineness throughout. If you could make a mixture containing charcoal of three different degrees of fineness—the first moderately fine, the next in pieces of the size of grains of ordinary sporting gunpowder, and the third of the size of large poppy seeds—and take equal parts of each of these three you will find that you have a mixture very serviceable for rocket purposes. But you can procure of Mr. Darby, whom I have mentioned before, a mixed charcoal which will save you the trouble of sifting. I recommend you, however, to use no charcoal that will not pass readily through your 20-mesh mixer, for your object is not to have your charcoal in large pieces, but to have a certain proportion of it coarser than the rest. You will find that the larger your proportion of coarse charcoal is, the slower your composition will be, and, within certain limits, the more fine charcoal you employ, the quicker it will be. Now, as the sparks produced by coarse charcoal remain visible in the air much longer and are much larger, than those produced by fine charcoal, I think it advisable to employ a good proportion of the coarse and in order to make up the strength that the composition loses by this plan, I take a smaller proportion of sulphur, as you will see by comparing formulas Nos. 1 and 2, and at the same time add a certain quantity of meal-powder. All these ingredients may be procured of Mr. Darby. The mode of mixing them is as follows:—Weigh out your quantities of nitre, sulphur, and meal-powder, mix them well together, and pass them through your 40-mesh sifter. This you will have no difficulty in doing, because the condition in which you purchase them is one of fine powder; your meal-powder especially cannot be too finely sifted for this purpose. You will find it a great convenience to add to this mixture a few drops of methylated spirits of wine or gin—a very slight quantity will suffice to render it less dusty—but you must bear in mind that whenever either of these liquids is employed, the composition will be sure to rust the steel spindle around which it is driven, unless you take the precaution of rubbing it over with a little oil or grease after using and before putting it away. Next add your charcoal. Stir the whole together, and pass the mixture two or three times through your 20-mesh mixer; by this means it will be thoroughly incorporated and fit for use.
ROCKET RAMMING.
6. Now we come to the actual ramming of the rockets; and, unless you intend to be a great nuisance to your friends and neighbours, you had better not dream of performing this operation indoors, it being productive of much noise and jarring; and you will find that they will not take much interest in your pyrotechnic progress when they have been annoyed and deafened by your frantic efforts for their amusement. You had better choose, therefore, some place either out-of-doors, or in an outhouse, where you are not likely to be interrupted or interfered with; the outhouse, of course, will be preferable, because there you will not be exposed to wind and weather, the former of which, especially, is often a source of considerable inconvenience when working out-of-doors. But whatever place you decide upon, you must have a very solid block of some kind, which is better made either of wood or stone, and must be set upon, or let into, solid ground. I should think that you will find no difficulty in meeting with one, made of either of these materials, in any carpenter’s or builder’s yard; odd pieces of stone and timber which would answer your purpose may generally be procured for a few pence. The stone block which I use is about 12 + 8 + 8 inches. On your block I recommend you to put nothing but the wooden block into which your spindle is fixed. The composition which you are using should never be placed upon it, because it is sure to become to some extent unmixed by the concussion caused by the blows of your mallet, for the particles of any coarse ingredient which it contains will find their way to the surface. You will find it advisable to have your block, and the table on which your tools and composition are placed, of such a height from the ground that, in working, you need not stoop or put yourself into any uncomfortable attitude.
Next we have to consider what is the most convenient receptacle for your composition while your cases are being filled with it. I use a copper scoop capable of holding about 8 ounces of composition, made something like an open coal-scuttle in form, which I have always found very convenient, and which is represented in the annexed woodcut (fig. 17).
[Illustration:
Fig. 17. ]
You will next require a small ladle made of thin copper or brass, of such a size that it will take up just as much composition as you should put into your case at a time, and will admit of being passed into the case. By means of this you will be able to drive in the composition very uniformly, for by giving a certain number of blows of a certain power to each ladleful, you can be sure of an equal compression throughout the length of the case. Such a ladle Mr. Newman will supply with your rocket tools, of the right size for filling ¼ lb. cases.
I will now suppose you to be ready at the ramming-block, with all your tools about you, your composition ready, and your case driven firmly down over your spindle. I strongly recommend a slight moistening of the composition as directed above before you begin to ram it. Now, taking the longest of the drifts (fig. 13) in your left hand, insert into the case when the first ladleful of composition has been put in. You are not to suppose that by “a ladleful” I mean as much composition as can be heaped up upon the ladle or scoop, but as much as will lie within it after you have passed the drift over its surface, and have levelled the composition to the height of its sides. To this first ladleful of composition give _fourteen_ blows with the mallet: it is not necessary to exert much force in this operation, for the weight of the mallet will be nearly enough to do the work for you; and you will find that after each stroke the mallet will recoil with the blow to a point almost high enough to be the starting-point for the next stroke. Having given the proper number of blows, take another ladleful of composition, and when you have put it into the case, drive it down in the same manner as the former one with the same number of blows. Then for your third ladleful take the longest drift but one, which must be used for this and the following ladleful, giving to each of them _sixteen_ blows. Then take the shortest hollow drift, and use this for as many ladlefuls as will make the composition rise to the top of the steel spindle, giving eighteen blows to each of them. Then by inserting the short, solid drift, you will be able to measure the distance between the top of the spindle and the top of the case. When you have taken this measurement, make a mark, on _the outside_ of the case, which will show you how high the spindle rises on the inside. By adopting this plan, or any other that may occur to you as simple, you will always be able to ram the same quantity of solid composition above the spindle. This is really an important matter, and one on which depends mainly the beauty of your rocket’s performance when it reaches its greatest elevation in the air. There are great varieties of opinion as to what should be the quantity of composition rammed solid above the spindle, and it is a much more common matter to find too little than too much composition used for this purpose. The effect of using too little is, that the rocket does not fairly arrive at its turn before its stars or other decorations are thrown out. This, in my opinion, is a considerable fault; for it robs the rocket of a great deal of the elegance of its flight, and gives one the idea that it is in a hurry to get its work over. Nothing but actual experience and observation will enable any one to decide which he considers the proper quantity of solid composition. I consider the best length for this part of the rocket to be that of _the exterior diameter of the case_—that is, an inch or rather more for rockets of the ¼lb. size. Larger rockets, I have always found, do not require quite so much in proportion; smaller rockets rather more. You should give twenty blows with the mallet to each ladleful of this solid composition. I am well aware that this number of blows sounds like a great deal of hard work, but you may rest assured that these twenty blows, given as I have directed above, will occupy only five or six seconds of time, at the cost of very little exertion.
Having now completed the ramming of the composition into your case, you will next require some common potter’s clay in dry powder; this can be procured of Mr. Darby in a condition proper for use. Take half-a-ladleful of it, and ram it down very hard upon the top of the composition with the solid drift. This clay when thus compressed will form an end to your rocket nearly as hard as stone—not so hard, however, but that you can bore a hole through it about ⁵⁄₁₆ths of an inch in diameter, which will allow of the necessary connexion between the rammed composition and the stars or other contents of the head of your rocket. In the next place I will speak of the
PRIMING.
7. This may be done in two ways; for exhibition purposes I should merely put into the mouth of the rocket some meal-powder-paste made as follows:—Make a rather soft, but not too liquid paste, by moistening meal-powder with gum-water made of the strength of 2-oz. of gum-arabic to a pint of water. With the flattened end of a stick rub some of this paste into the cup formed at the choked end of the rocket, taking care that none of it _is left in the choke_ or narrow aperture at which the fire from the rocket has to find vent; for, if any should remain there, the rocket when fired is almost certain to burst. Any of the paste that happens to be forced into this aperture may easily be taken out afterwards by means of a piece of wire or stout pin.
Your rocket is now finished as far as its ascending power is concerned.
ROCKET POT.
[Illustration:
Fig. 18.—Pot-former. ]
[Illustration:
Fig. 19.—Rocket pot. ]
8. I will tell you my method of making the head, or _pot_ as it is termed, of the rocket. You must have a piece of hard wood turned of a shape like that indicated in the following woodcut (fig. 18). The straight part of this should be about 4 inches long, and a shade larger in diameter than the exterior of your rocket-case—that is, about 1⅛ inch in diameter, if you adopt the method of cutting up your imperial board and 70-lb. brown paper given in _this_ chapter. Now take some moderately thick brown paper, and cut it into strips about 5 inches in width and 8 in length; each of these strips will be long enough to go twice round the _pot-former_ described above. When you have pasted as much of each strip as will not lie actually against the former, roll it up straightly and pinch in one end; you will thus have made a cylinder of paper (fig. 19) closed at one end, the other end of which will fit nicely over the clay end of your rocket. This is the pot of the rocket, which is to contain your stars, rains, &c.
ROCKET CONES.
[Illustration:
Fig. 20.—Cone-former. ]
[Illustration:
Fig. 21.—Paper for Cone. ]