2021-04-18 11:27:33

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ENGLISH A new design should be based upon one of two suppositionseither that existing mechanism is imperfect in its construction, or that it lacks functions which a new design may supply; and if those who spend their time in making plans for novel machinery would stop to consider this from the beginning, it would save no little of the time wasted in what may be called scheming without a purpose.CHAPTER XXI. MECHANICAL DRAWING.

Very large divisions marched from Vis to the pontoon bridge in the direction of Tongres. After the Lige forts had been taken the bridge might be passed in perfect safety. All day long troops came along that road without interruption. I could quite see that the soldiers who were at Vis the previous day, and brought about the conflagration, were gone, for they had left their traces behind. All along the road lay parts of bicycles, shoes, instruments, toys, and so on, everything new77 and evidently looted from the shops. Very valuable things were among them, everything crushed and smashed by the cavalry horses, the clumsy munition and forage waggons, or the heavy wheels of the guns.Machine motion is mainly rotary; and as rotary motion is accomplished by cylindrical parts such as shafts, bearings, pulleys and wheels, we find that the greater share of machine tools are directed to preparing cylindrical forms. If we note the area of the turned, bored and drilled surface in ordinary machinery, and compare with the amount of planed surface, we will find the former not less than as two to one in the finer class of machinery, and as three to one in the coarser class; from this may be estimated approximately the proportion of tools required for operating on cylindrical surfaces and plane surfaces; assuming the cutting tools to have the same capacity in the two cases, the proportion will be as three to one. This difference between the number of machines required for cylindrical and plane surfaces is farther increased, when we consider that tools act continually on cylindrical surfaces and intermittently on plane surfaces.

To illustrate the practical application of what has preceded, let it be supposed, for example, that a machine is to be made for cutting teeth in iron racks ? in. pitch and 3 in. face, and that a design is to be prepared without reference to such machines as may already be in use for the purpose.This terrible tragedy took place at scarcely six yards from the Netherland frontier, for the burgo101master's house stands by a road half Belgian and half Netherland. The Netherland soldiers who were doing frontier-duty on the latter part had to fly from the mad shooting of the Germans. They hid behind a wall that was quickly full of bullet-holes. The German soldiers spent a considerable time guzzling the burgomaster's wine, which they looted, and afterwards went off in the direction of Tongres.

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The town was on fire, and ruddy smoke hovered over it. Deserted like a wilderness, not a soul moved in the streets. The first street I entered was the Rue de la Station. Large, imposing mansions used to stand here, but the devouring fire consumed even the last traces of former greatness.Founding and casting relate to forming parts of machinery by pouring melted metal into moulds, the force of gravity alone being sufficient to press or shape it into even complicated forms. As a process for shaping such metal as is not injured by the high degree of heat required in melting, moulding is the cheapest and most expeditious of all means, even for forms of regular outline, while the importance of moulding in producing irregular forms is such that without this process the whole system of machine construction would have to be changed. Founding operations are divided into two classes, known technically as green sand moulding, and loam or dry sand moulding; the first, when patterns or duplicates are used to form the moulds, and the second, when the moulds are built by hand without the aid of complete patterns. Founding involves a knowledge of mixing and melting metals such as are used in machine construction, the preparing and setting of cores for the internal displacement of the metal, cooling and shrinking strains, chills, and many other things that are more or less special, and can only be learned and understood from actual observation and practice.

Dimension lines should be in blue, but may be in red. Where to put them is a great point in draughting. To know where dimensions are required involves a knowledge of fitting and pattern-making, and cannot well be explained; it must be learned in practice. The lines should be fine and clear, leaving a space in their centre for figures when there is room. The distribution of centre lines and dimensions over a drawing must be carefully studied, for the double purpose of giving it a good appearance and to avoid confusion. Figures should be made like printed numerals; they are much better understood by the workman, look more artistic, and when once learned require but little if any more time than written figures. If the scale employed is feet and inches, dimensions to three feet should be in inches, and above this in feet and inches; this corresponds to shop custom, and is more comprehensive to the workman, however wrong it may be according to other standards.When I drove into Namur, I found the town comparatively quiet; there was some traffic in the streets, and Belgian army surgeons and British nurses in their uniforms walked about freely.154 There were many wounded: the German wounded were all placed in the military hospital; the Belgians and the French had been taken to the Sisters of Mercy, the Institution Saint Louis, the High School for Girls, and the Sisters of Our Lady.

"How did that come about?"It was a fantastic night. Trains arrived out of the foggy darkness, their screeching whistle resounding from the far distance, and when they steamed into the station a storm of noise arose. All these trains brought British prisoners of war, captured by the Germans at St. Quentin, and hundreds of German soldiers escorted the trains, which were all covered over with green branches, and looked like copse-wood sliding along the railroad. As soon as they rumbled into the station the escorts sang loudly their patriotic songs, and "Germany before all other!" ("Deutschland über Alles!") vibrated through the fog.

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In the use of hydraulic apparatus for transmitting and applying power, there is, however, this difficulty to be contended with: water is inelastic, and for the performance of irregular duty, there is a loss of power equal to the difference between the duty that a piston may perform and what it does perform; that is, the amount of water, and consequently the amount of power given off, is as the movement and volume of the water, instead of as the work done. The application of hydraulic machinery to the lifting and handling of weights will be further noticed in another place.The turn things took now was not quite to my liking, and I did not feel very safe when I handed him my scribbling-pad.

"10. Falloise, alderman.The dust-wall extended gradually as the distance grew covered by the Germans in their flight to their former positions. But at last we saw the first men emerge in complete disorder from that driving cloud. Some on the right, others on the left, here60 and there also small groups which courageously dragged their guns with them, as they saved themselves from that infernal downpour.

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Apr-18 11:27:33