Mechanical device

“ Examine at random any one of half a dozen lines of mechanical invention, one characteristic common to them all will instantly arrest attention—they present nothing more than a mere outgrowth of the manual processes and machines of earlier times. Some operation, once performed by hand tools, is expedited by a device which enables the foot as well as the hand to be employed. ”

“ Yet this remarkable contrivance, with all its massive steel beams and chains and cog wheels, employs no other principles than the simple ones of lever and pulley and inclined plane that we have just examined. The power that must be applied to produce a given effect may be calculated to a nicety. The capacities of the machine are fully predetermined in advance of its actual construction. But of course this is equally true of every other form of power-transmitter with which the modern mechanical engineer has to deal. ”

“ The mechanical powers are usually enumerated as follows:—The pulley, the lever, the wheel and axle, the wedge, the inclined plane, [Pg 101] the screw. These different powers are so frequently used in combination that the distinctions cannot be always maintained. The classification will, however, suffice to give a general notion of the subject.
186. Many of the most valuable mechanical powers are machines in which ropes or chains play an important part. Pulleys are usually employed wherever it is necessary to change the direction of a rope or chain which is transmitting power. ”

“ The machine is driven by power from a shaft or a motor and is so geared that various speeds are obtainable. One man can operate it.
In making tests the operation of the straining screws is always downward so as to bring pressure to bear upon the weighing platform. For tests in tension and cleavage the specimen is placed between the top of the stationary cage and the movable head and subjected to a pull. For tests in transverse bending, compression, and cleavage the specimen is placed between the movable head and the platform, and a direct compression force applied. ”

“ Had it been otherwise, an animal running on its own wheels would have made its appearance on earth long ago. The shaft of the steam engine could be provided with numerous pulleys, each capable of driving a machine connected with it by a belt. Then arose that marvellous crop of mechanical combinations which brought about the age of mechanism, combinations which, in the last resort, can be reduced to sliding couples and turning couples, and can be catalogued by means of formulæ, like words in a dictionary. ”

“ That handle at the side, like the handle of a barrel organ, serves to wind up the spiral spring of the mechanism. The arrow here in this slot regulates the celerity of the strokes. At the height of the pillar, in a little glass case, is a mechanical meter or indicator. This enables one to check the accuracy of the working of the machine, and is also useful for statistical and revisionary purposes. ”

“ Patents have been granted for many ingenious mechanical combinations to impart to the propelling surfaces such angles as appeared to the respective contrivers most advantageous. In most of these, however, the mechanical complexity has formed a fatal objection. ”

“ The velocity ratio of the former machine is nearly double that of the latter, and its mechanical efficiency is nearly four times as great. Less than half the applied power is wasted in the wheel and axle, while more than half is wasted in the differential pulley. This makes the wheel and axle both a more powerful machine, and a more economical machine than the differential pulley. ”

“ The machine, which towers thirty feet into the air and completely dwarfs the attendant, who has it as thoroughly under control as if it were a small file, bites great shining strips forty feet long, maybe, off the surface of the passive metal, and leaves a series of grooves as truly parallel as the art of man can make them. There is no fuss, no sticking, no stop, no noise; the force [71] of electricity or steam, transmitted through wonderfully cut and arranged gear-wheels, is irresistible. ”

“ We are far from having described all the implements of the mechanical engineer, or even all the more interesting ones; for example, we have given no account of the powerful lathes in which great masses of iron are turned, or of the analogous machines, which, with so much accuracy, shape the internal surfaces of the cylinders of steam engines, of cannons, &c. ”

“ Whenever more than half the applied energy is consumed by friction, the load will remain without running down when the machine is left free.
THE EPICYCLOIDAL PULLEY-BLOCK.
223. We shall conclude this lecture with some experiments upon a useful mechanical power introduced by Mr. Eade under the name of the [Pg 117] epicycloidal pulley-block. It is shown in Fig. 33, and also in Fig. 49. In this machine there are two chains: one a slight endless chain to which the power is applied; the other a stout chain which has a hook at each end, from either of which the load may be suspended. ”

“ In the Emery system of machines, consisting of scales, gages, and dynamometers, the power exerted on the material tested is transmitted from the load to an indicating device by means of liquid acting on diaphragms. ”

“ To this end illustrations will be given of the most recent arrangements of Horizontal, Vertical, Beam, Pumping, Winding, Portable, Semi-portable, Corliss, Allen, Compound, and other similar Engines, by the most eminent Firms in Great Britain and America. The laws relating to the action and precautions to be observed in the construction of the various details, such as Cylinders, Pistons, Piston-rods, Connecting-rods, Cross-heads, Motion-blocks, Eccentrics, Simple, Expansion, Balanced, and Equilibrium Slide-valves, and Valve-gearing will be minutely dealt with. ”

“ An electric motor is a machine for transforming electric energy into mechanical power.
[204]
While the electric motor is similar in construction to the dynamo, it is opposite to it in action. Motors receive current and produce motion. The motion is a rotary one, the power being applied to other machines by means of belts or gears.
Fig. 164.
EXPERIMENT 200. To study the action of the telephone.
478. Directions. (A) Join the ends of coil H (Fig. 164) to the astatic galvanoscope. Move magnet M back and forth in front of the soft iron core, while H is held in position. Watch the needle. ”

“ This is followed by the mathematics necessary for the solution of the problems in machine design which are presented later, and a practical introduction to theoretical mechanics and the strength of materials. The various elements entering into machine design, such as cams, gears, sprocket wheels, cone pulleys, bolts, screws, couplings, clutches, shafting and flywheels have been treated in such a way as to make possible the use of the work as a textbook for a continuous course of study. It is easily comprehended and assimilated even by students of limited previous training. ”

“ THE MOTOR You will remember that the armature consists of a spool wound with wire. This spool is made of iron plates fastened together so as to form one solid piece. The armature of a motor may be made in the same way; in fact, the whole motor is practically a dynamo-machine. ”

“ In order to prevent shock when the machine alights, it is necessary to provide something that is strong and, at the same time, yielding, and able to travel through a considerable distance before the machine comes to a state [80] of rest. In the machines which I have seen on the Continent, a very elaborate apparatus is employed, which is not only very heavy, but also offers a considerable resistance to the forward motion of the machine through the air. It consists of many tubes, very long levers and heavy spiral springs, etc. ”

“ A gear-cutting device is also applied in the same manner, as well as plain or universal work-holding centres.
The essential features of the machine are a standard a, Fig. 1894, with spreading base, carrying upon its top a driving cone b, which is fully back-geared like an engine lathe. The driving cone operates also the feed mechanism. Above the driving cone is an arch c, in which is inserted an arm d for supporting the outer end of the mill arbor when used for heavy work. ”

“ In those mechanical parts of machines which are hardened to resist abrasion and wear, the quality or grade of the steel is very often selected with a view to obtain strength in the parts and ease of mechanical manipulation in cutting them to the required shape, rather than to the capacity of the steel to harden. ”

“ Although machines designed for construction and use in space may employ radically different components than their terrestrial counterparts, to a first approximation it may be assumed that they will be comprised generally of the same kinds of parts found in commonplace machines on Earth such as bolt, nut, screw, rivet, pulley, wheel, clutch, shaft, crank, rod, beam, wire, plate, disk, bushing, cable, wedge, key, spring, gasket, seal, pipe, tube, and hose. ”

“ The printing roller C is the only part of the machine directly connected with the motor or main drive of the works through the cog-wheel on its axlethe “ mandril ”-all the other parts deriving their motion from it, either by friction as in the case of the cylinder or by a spur wheel as in that of the colour-furnishing roller. ”

“ These machines, when large, are worked by a steam-engine, and their mode of operation is as follows:—The nucleus of the machine is a system of powerful permanent steel magnets, and a conducting coil is made to revolve rapidly in presence of these magnets. ”

“ The high pressure steam engine, in whatever form it exists, consists of a frame or bed plate carrying two distinct mechanisms, first, the driving or power-transmitting mechanism, and second, the valve gear or valve motion, and to these are added such other mechanisms as the nature of the duty the engine is to perform may require. ”

“ At each side of the Machine (see figs. 1 and 2) is fixed on a centre i, a short lever k l, the bent end of which (l) rises just to the brass step which carries the mandrel of the cylinder a, and is formed so as to push that step inward, when it’s end k is pressed outward; which latter motion is occasioned by the screw m n, which goes all across the Machine, and performs the same office on either side as wanted. This then, is another economy of time and pains; this setting being usually done by passing round the Machine, from one side to the other. ”

“ NO. 2.—IMPROVED ENGINE LATHE.
This again is a highly valuable and ingenious machine; its special operation is, as its name implies, the turning of any iron work to its required round circumference and requisite degree of polish, whether it is a perfect cylinder, or of various diameters at various points.
By it, all round work for engines is formed and finished—as rods, shafts, and the like. The action of the machine is simple, easy and almost noiseless. ”

“ Such machines as are used in shaping materials in the construction of the parts of other machines, and also many of those which perform work, such as boring, planing, riveting, etc., formerly only done by hand, and still performed manually to a greater or less extent, are nearly always called machine tools; the term, engine tool, is more in accord with general usage when referring to large and complicated machines. ”

“ Or suppose you have an idea for a gyro-motor such as are used for driving aeroplanes. Now in this motor the shaft to which the pistons are fastened stands still and the cylinders in which the pistons move revolve. It is rather a curious motion and not easy for a fellow who is not posted on mechanics to grasp offhand.
What’s the thing to do? Why, make a cardboard [44] model of the mechanism using pins for the shafts and you will have a model that will look like Fig. 33, and when you turn the cardboard disk with the cylinders marked on it you will see at once exactly how the motor works. ”

“ Assuming the relation of these sets of magnets to be one of equality, he has constructed a motor, in which the cores of the field-magnets are light pieces of soft iron, that gives very satisfactory results. Further experiments to determine the exact ratio of the power of the field and armature, he believes, will result in a much more perfect machine. ”

“ This rule is true for all kinds of levers, blocks and tackles or pulley systems, automobile and bicycle gears, belt systems, cog systems, derricks, crowbars, and every kind of machine. In most machines you either put in more force than you get out and gain motion, or you put in more motion than you get out and gain force. ”

“ This clumsy machine is now replaced by the very simple invention which has been in vogue for some years, and which can not only release, but regulate, the pressure at any moment, by means of springs, levers, and weights. This machine is, in fact, exactly the same as that which is represented in the illustration, except that the rollers are quite smooth. They can be adjusted to almost any amount of pressure by levers and weights which are attached to the upper roller, and, when the linen has passed through them, it has undergone the double operation of wringing and mangling. ”

“ Geared Rubber Motors.—It is quite a mistake to suppose that any advantage can be obtained by using a four to one gearing, say; all that you do obtain is one-fourth of the power minus the increased friction, minus the added weight. This presumes, of course, you make no alteration in your rubber strands. ”

“ Machines are made of a variable number of carriers to suit goods of different character that are required. Provision is made to carry the rubber beam in hanging brackets underneath the machine, which are of sufficient strength and firmness to carry the maximum weight necessary for governing the rubber tension. Above the machine there is a gear-driven take-up shaft, on which are tension rolls to govern the feed of the goods when braiding. ”