The chief parts of this complicated machine being now described, at a length as great as the limits of our work can admit, and perhaps tiresome to some readers, the mechanical description shall be concluded with sonic remarks upon that part of the machine, which is, of all others, that which requires the greatest portion of atten tion, and upon the accuracy of which the chief, if not the only difficulty, in actual practice was found. This lies in the construction of the needle, and apparatus be longing to it ; and what illustration can be given by re presentation, without a great multiplication of figures, will be found in Figure 2. Plate CXXXVII.
The tambourin bears so strong an analogy to the stocking manufacture in the chaining, that at first the experiments were made with needles in every respect similar to those of the stocking frame, that is to say, with bent pieces of iron-wire, shut by the pressure of an iron bar, and re-opened by their own spring or elasticity, A very few trials proved this to be inapplicable to tam bouring, for three reasons : The first of these was, that, by bending the wire, the flexure, which really formed the point of the needle, was too blunt to perforate the cloth, without risk of injury to the fabric ; and the metal was too weak to bear sharpening after the flexure was made. The second was, that the pressure of the bar which shut the barbs, also made the stems yield very considerably, and this was apt to injure the cloth. The third reason was, that, in order to present the barbs to the action of the pressing bar, the needles required con stantly to be brought back from the position necessary for the pattern, to one where the barbs would be verti cally over the stems. ln order to remove all these ob jections, a principle was adopted, by which all those ob jections were removed. The hook, or needle, was ma nufactured from solid wire. The barb was made very short, like that represented in the figure. The closing of the barb was effected by a small slider belonging to each needle, and the pressing- bar entirely removed. The barb of the needle was cut like those of common fishing hooks; and, like them, the needles were made from , steel wire, so as to be susceptible of tempering. This afforded a facility of sharpening the points, as much as those of sewing needles, and removed the other objec tions, as they could now be opened and shut in any posi tion. In this improved state, their appearance will be found very much such as in Figure 2. This figure re
presents a section of the needle frame, the rack by which the handles are made to revolve, and all the ap paratus for opening and shutting the needles. The point and barb of the needle appear at a; and the slider, which is partially sunk in a groove, sunk longitudinally in the stern of the needle, is at b. The slider is merely a piece of pointed wire, which has also a longitudinal groove, and is pointed pretty sharp. The slider was at first fixed to a piece of flat brass, with waxed silk, as fishing hooks are tied ; but the silk being often eut, by friction and other causes, it was found better to cast a socket of tin round them, of the shape which the figure represents in profile. At c is a socket of brass, bored so as to fit the handle exactly, and slide freely upon it. The upper part of this socket being flattened, to receive the tin into which the slider is cast, they were screwed together; a slot being cast in the tin to allow it in slide a little back ward or forward, for the purpose of fitting the tin, so that the points of the slider and needle might correspond when shut. At f is a section of a cast-iron bar extending across the machine, being the same as is represented in Fig. I. Plate CXXXV1. at E. By the oscillatory move ment of this bar, the sockets slide backward and lbr ward on the handles, to open and shut the needles, each socket being grooved to admit a notch of the bar. The handle is at g, the pinion at h, and a profile of the rack at i.
These arc the principal mechanical parts of the ma chine, which has been found to answer very well, and is still in use. Its chief defect is its complexity, and the fanciful nature of the work for which it is employed. For this reason, the reader will perhaps pardon the lengthen ing of the article a little, for the purpose of considering its practical economy, in point of expellee, produce, and return, especially as those remarks are accompanied by a description of another machine, since invented, by the writer of this article, the expence of which :kt ill not ex ceed one-tenth part of that of the present, and whose product must be vastly greater. It is also so different in its principle, as to invade no one particular upon widen the former patent rests for its validity. Mechanie I descriptions, in general, also so very seldom embract considerations of economy, or mercantile calculation any kind, as often to be dangerous, instead of proving really useful.