To give the reader a clear insight into the mode of working a bar through the rolls, it appears to be necessary partly to repeat what has been before but imperfectly noticed. A bar of iron, as it passes through each successive groove of a pair of rolls, is received on the opposite side by two men, one of whom draws it out by the end with a pair of tongs, and the other supports it by a lever to prevent its making too sudden a bend; and when the bar is through, these men pitch it back again over the top roll for it to pass through the next groove; and this operation is repeated until the bar is reduced to the required size. Now it must be evident upon reflection, that this returning of the bar over the rolls occupies about as much time as the actual rolling; consequently that the iron becomes cooled in proportion, harder, and requires more power to roll it; that the workmen have a very severe labour to perform, and are all the while exposed to a scorching heat. These defects in the ordinary process of rolling forcibly struck the writer several years ago, when he proposed two methods of continuous rolling, by which it was estimated that the manual labour would be greatly reduced, the personal inconvenience diminished, the cost of the machinery lessened, and one-half of the power of the engine saved.
The first of these plans was to place a series of pairs of small rollers (that is, short in their axes) one before the other, so that the bar might pass in one continued straight line, from groove to groove, until finished of its intended dimensions. This plan is explained by the annexed diagram; a a, bb, and c c, represent the transverse sections of three pair of rollers, with grooves of different depths; the bar is supposed to enter at d, and by passing through the rollers a a to be reduced to the size e, where the bar slides upon a form h, guided thereon in a straight line by a furrow of the shape of the bar, direct into the grooves of the rollers bb; the bar of the size of e is here reduced to that of f, lying on another form h, which conducts it through the rollers e e, and is thereby further reduced to the size of g, or any other that may be required by a suitable extension of the apparatus. By this method it was considered that a bar would be rolled in about one-third the usual time; that the manual labour would be reduced to a trifling amount; and that not one-half the usual power required of the engine would be absorbed.
The latter advantage results from the celerity of the operation; for as the iron is much hotter, it is much softer, and requires a less amount of force, even during the diminished time taken up by the process; but the most important advantage is, that a better bar is thereby made; when the maxim to " strike the iron while it is hot," has thus been duly attended to, the bar, instead of being cracked at its edges or otherwise unsound from being rolled when too cold, will be uniformly solid and of a more perfect form.
The second plan devised was to put a series of small rollers one above another, with the usual spur gear on their axes, which would give every succeeding roller an opposite rotation, so that the bar might enter between the first and second roller, go back through the second and third roller, then through the third and fourth, the fourth and fifth, and so on to completion. In the annexed, Fig. 2 affords a side elevation, and Fig. 3, on the following page, a vertical section of six small rolls, abcdef, which, by their arrangement, are in effect five pairs. In Fig. 3 the letters ghikl, show the situation of five shelves, (the proportionate length of which cannot be shown,) on which the iron slides; and the arrows in the same figure indicate the course taken by the bar through all the rolls. The shelf g is supposed to be upon a level or somewhat lower than the mouth of the furnace, the bloom from which is to be slided down upon g, and pushed between the rollers a and b, and as it passes out of these, it gradually bends down, the end falling in the position of the arrow at h, ready to enter between the rollers b and c; then upon i between c and d, upon k between d and e, upon l between e and f, and so on to any number of rolls underneath, or be conducted forward to another series of rollers placed before it.
Both the plans now described may be employed separately or jointly; but for various reasons the vertical series would be preferable for roughing the work, while the horizontal arrangement would probably be best suited for finishing the work. It is to be understood that the foregoing diagrams are only designed as explanatory of the principle of construction, all the subordinate details being omitted as unnecessary in this place. Previous to the year 1828, the writer had never seen nor heard of iron being rolled on either of the plans described; he had seen several iron works, one newly built, in none of which, however, was the principle adopted; he could find no published account of any thing of the kind; his mechanical friends said the plans were new and valuable, and a patent was determined upon if the opinions of two or three respectable iron masters, whom he consulted, should be favourable; when, singular to relate, two of these persons, who had very extensive concerns, condemned the plans as useless and impracticable, while the third said they were not only practicable, but highly advantageous; and he proved the truth of his assertions by showing the writer his works, wherein iron was at that time being rolled on the very principle of both plans, where he was informed it had been practised for several years; and that similar rolls were used in several of the works of Staffordshire! This fact has been mentioned with the view of inculcating circumspection in inventors before they incur the expense of patents, and a disregard of dogmatical opinions when unsupported by reason.
It is worthy of remark in this place, that in none of the recent treatises on the iron manufacture has any notice been taken of this important improvement in rolling iron. The plan at the iron works where the writer saw the principle in operation, is a modification of that which has been described; it consists of only three rolls one above another, but of the same kind as those delineated at page 775, so that a bar which has passed through a groove between the top and middle roll is sent back through another groove between the middle and lowest roll; and there being many grooves in each of the three rolls, they are thus passed alternately through the upper and lower range of grooves until completed; but in making vat hoops, the bar, after being passed through several grooves, to roll it to a thin, yet rough flat bar, proceeded onward horizontally (in the same manner as shown in the diagram, page 776), and entered between a pair of plain polished rolls, where it was reduced to the required thinness, and a smooth face was given to it.