The illustrations herewith exhibit a number of devices of various kinds, well known to the practical mechanician and professional engineer, and usually called mechanical movements. It is estimated there are no less than 1,500 of these movements doing service at the present day; but many of them are, of course, quite complex, and difficult to master. In this book, I show about one hundred of the simplest sort, or those in common use. Their usefulness will at once be appreciated if we refer to [Fig. 102], which shows a machine for grinding or breaking up substances within its capacity. It contains within itself the true principle of the little mill used to grind coffee. The word "grind" in this connection is scarcely the right one, as the mill rather "crushes" or breaks up, than grinds. You will notice coffee, ready for use, is coarse and unlike flour in texture, the latter being "ground" fine and smooth. In grinding, the abrading surfaces are brought very much closer together than in the breaking or crushing processes. In a coffee mill, the berries or grains drop into a vacancy, left between the revolving cone and the walls of the mill. The vacancy between the walls and the cone is a little less at the bottom where the crushed coffee is discharged, and this enables the small and large grounds to fall into the drawer. The detailed plan in illustration ([Fig. 102]) shows a mill complete, as well as the various parts. It will be noticed that the cone (Fig. [5]), is corrugated or grooved as shown (Fig. [4]). Figs. [6] and [7] show sections of lining at B and C (Fig. [3]). A shows the hopper into which the coffee berries are placed before grinding. Figure [9] shows the crank detached, and Figs. [8] and [10] show the remaining parts of the machine, while Figs. [1] and [2] show the handle and drawer. The latter is to receive the ground or crushed coffee after it has gone through the mill. Further description is unnecessary if we take for example the movement represented at [Fig. 150], which is a sort of ball-bearing motion, only instead of small balls wheels are used. Besides being made use of in bicycles in small balls, it is used as depicted for "hanging" grindstones, and for many other similar purposes.
The device also shown at [Fig. 139], is one in common use. It is a modification of the sprocket wheel on the bicycle. Many of the devices shown herewith are rarely noticed because of our familiarity with them.
The action of pumps, the working of pistons, the changing of motion, and many other things are shown and explained in the little illustrations given in these descriptions, which do not pretend to be exhaustive, or even full.
[Fig. 103]. In this the lower pulley is movable. One end of the rope being fixed, the other has to move twice as fast as the weight, and a corresponding gain of power is consequently effected.
[Fig. 104] is a simple pulley used for lifting weights. In this the power must be equal to the weight to obtain equilibrium.
[Fig. 105]. Blocks and tackle. The power obtained by this contrivance is calculated as follows: Divide the weight by double the number of pulleys in the lower block; the quotient is the power required to balance the weight.
[Fig. 106] represents what are known as "White's pulleys", which can be made with separate loose pulley; or a series of grooves can be cut in a solid block, the diameters being made in proportion to the speed of the rope; that is, 1, 3, and 5 for one block, and 2, 4, and 6 for the other. Power as 1 to 7.
Figs. 103, 104, 105, 106, 107. Various phases of block and tackle