Force Author:Jacob Abbott Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER IH. MECHANICAL FORCE. In the case described in the last chapter, the function of the grindstone, in respect to its action as a fly-wheel, was this,... more » namely, to receive the force in the form of a succession of impulses imparted by the weight of Rick at each revolution of the crank, and then to deliver it, at the surface of the stone, in an equable and continuous flow. In some cases, however, the action of a fly-wheel is the reverse of this. It receives the motion in a continuous flow from the machinery by which it is driven, and delivers in a succession of impulses, when such impulses—that is to say, intermittent exertions of force—are required by the nature of the work to be done. Such intermittent action, for example, is required in the case of such an engine, as is shown in the accompan ying engraving, for cutting off heavy iron bars into portions of a given length. It seems wonderful that bars of such thickness can be cut offin this manner at PONDEROUS SHEARS. 37 a single stroke by a pair of shears. But there is no difficulty in doing it, and that, too, with great rapidity, provided that a sufficient force to overcome the cohesive strength of such a mass of iron is accumulated in the immense fly-wheel, which always forms a part of such machinery, and is brought to the work by a band or some other connection, and that the jaws of the shears are made massive and solid enough to hold the force and deliver it all at the precise point or line in the iron bar where it is required. The iron is cut off in such a case as if the bar was one of wax. The portions are made equal by means of the gauge seen toward the right, against which the workman, after each portion is cut off, pushes the bar, and thus measures another portion to be cut off at the next descent of ...« less