Sec. III. Of Rammers, Chargers, and Mallets.
The rammers which are used for compression, are cylindrical like the preceding. They have a head much larger in dimensions than the part that enters the tube. (See A, B, C, D, and E of Fig. 1. in [the Plate]). Besides being made of wood, which should be of the hardest kind, as lignum vitæ, they may be formed of copper or brass. In this case, they are first cast of the requisite size and shape, and finished in a lathe. Wooden heads are sometimes put to them, but with little advantage; as they frequently split and require to be renewed.
The wooden rammer may be struck with metal; but when the rammer is of copper or brass, wooden mallets must be always employed.
We may here remark, that in charging rockets, it has been customary to employ several rammers. The first drift must be six diameters from the handle, and this, as well as all other rammers, ought to be a little thinner than the former, to prevent the tearing of the paper, when the charge is driven in. In the end of this rammer is a hole to fit over the piercer. (See [B. Fig. 1.]) The line marked on this rammer, as will be explained hereafter, when it appears at the top of the case, indicates that a second rammer must be used. This second rammer, from the handle, is four diameters, having a hole for the piercer, 11/2 diameters long. (C. Fig. 1.) When the case is filled as high as the top of the piercer, a short and solid drift is used. (E. Fig. 1.).
Rammers must have a ferrule, or collar of brass at the bottom, to keep the wood from spreading, or splitting. With regard to the handles of the rammers, if their diameter be equal to the bore of the mould, and two diameters long, the proportion is a good one. The shorter they can be used, the better. The longer the drift, the less of course, will be the pressure on the composition, by the blow given by the mallet.
We may observe here, that rockets may either be driven over a piercer, or driven solid, and afterwards bored.
As much of the effect of rockets depends upon the manner they are driven, whether lightly or compactly, or uniformly throughout, circumstances which affect their quality; it is necessary, in using the rammer, to employ an equal force for driving the composition. The mallet, therefore, should be of a given weight; and a certain number of strokes with the same force, on each new charge, must be accurately followed, until the driving is completed; taking care, at the same time, that the rocket stands firm on a solid body.
Dry beech is the best wood for mallets. A writer very judiciously observes, in the Encyclopedia Britannica, (vol. xv, 695), that, if a person uses a mallet of a moderate size, in proportion to the rocket, according to his judgment, and if the rocket succeeds, he may depend on the rest, by using the same mallet; yet it will be necessary, that cases of different sorts, be driven with mallets of different sizes. In all cases, under one ounce, the charge may be rammed with an ounce mallet.
There is an advantage, also, by having the handle of the mallet turned out of the same piece as the head, and made in a cylindrical form. If their dimensions are regulated by the diameters of the rockets; then, for example, if the thickness of the head be three diameters, and its length four, the length of the handle will be five diameters, whose thickness must be in proportion to the hand.