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ENGLISH bt波多野结衣无码下载地址A pattern-maker no sooner sees a casting than he imagines the kind of pattern employed in moulding it; a moulder will imagine the plan of moulding and casting a piece; while an engineer will criticise the arrangement, proportions, adaptation, and general design, and if skilled, as he ought to be, will also detect at a glance any useless expense in patterns or moulding.To exert a powerful force acting through but a short distance, percussive devices are much more effective and simple than those acting by maintained or direct pressure. A hammer-head may give a blow equal to many tons by its momentum, and absorb the reactive force which is equal to the blow; but if an equal force was to be exerted by screws, levers, or hydraulic apparatus, we can easily see that an abutment would be required to withstand the reactive force, and that such an abutment would require a strength perhaps beyond what ingenuity could devise.Count Rumford did not by chance develope the philosophy of forces upon which we may say the whole science of dynamics now rests; he set out upon a methodical plan to demonstrate conceptions that were already matured in his mind, and to verify principles which he had assumed by inductive reasoning. The greater part of really good and substantial improvements, such as have performed any considerable part in developing modern mechanical engineering, have come through this course of first dealing with primary principles, instead of groping about blindly after mechanical expedients, and present circumstances point to a time not far distant when chance discovery will quite disappear.
I went to bed early, for that day I had again walked from Maastricht to Lige. My little bedroom was quite in the roof of the house, and had evidently been used by a servant."Oh no, sir, not at all!"Shaping machines as machine tools occupy a middle place between planing and slotting machines; their movements correspond more to those of slotting machines, while the operation of the tools is the same as in planing. Some of the advantages of shaping over planing machines for certain kinds of work are, because of the greater facilities afforded for presenting and holding small pieces, or those of irregular shape; the supports or tables having both vertical and horizontal faces to which pieces may be fastened, and the convenience of the mechanism for adjusting and feeding tools.
(1.) What is the difference between boring and drilling?(2.) Why will drills endure more severe use than other tools?(3.) Why is hand feeding best suited for drills?(4.) What is the difference between boring with a bar supported on centres and one fed through journal bearings?Shortly afterwards I met a Netherland Red Cross motor-car. The male nurses, who had met me already on former occasions during the war, recognised me, rushed up to me, and forced me to come with them to the car. Here they tried to explain with a torrential flow of words that I exposed myself to the greatest danger by coming here, as nearly all the soldiers were drunk, shot at every civilian, and so on.
"In Amsterdam...."It is not proposed at this time to treat of the construction of machinery for transmitting power, but to examine into the conditions that should determine which of the several plans of transmitting is best in certain caseswhether belts, gearing, or shafts should be employed, and to note the principles upon which they operate. Existing examples do not furnish data as to the advantages of the different plans for transmitting power, because a given duty may be successfully performed by belts, gearing, or shaftseven by water, air, or steamand the comparative advantages of different means of transmission is not always an easy matter to determine.Some uphold the accusation on the ground of expressions in Belgian newspapers, collected in a German pamphlet. In my opinion these quotations have not the slightest value. Everyone will understand this who thinks of the excitement of journalists, whose country was suddenly and quite unexpectedly involved in a terrible war, and who felt now that as journalists they had to perform a great, patriotic duty. In their nervous, over-excited condition they sat at their desk and listened to the gossip of refugees about civilians taking part in the struggle. In their imagination they saw hordes of barbarians overrun their native soil, saw man and man, woman88 and woman, shoulder to shoulder, resisting the invader without regard for their own life. The thoughts of such journalists, whose very own country had been at war now for a few days, were not on severe logical lines; they found a certain beauty in that picture, and I can quite understand how some came to believe in it as a reality, and gloried in it.
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.In sketches and drawings made for practice, such as are not intended for the shop, it is suggested that metrical scales be employed; it will not interfere with feet and inches, and will prepare the mind for the introduction of this system of lineal measurement, which may in time be adopted in England and America, as it has been in many other countries.
"Are they tolerably kind?""But ... but ...! May I go there?"CHAPTER III
Tempering, as a term, is used to comprehend both hardening and drawing; as a process it depends mainly upon judgment instead of skill, and has no such connection with forging as to be performed by smiths only. Tempering requires a different fire from those employed in forging, and also more care and precision than blacksmiths can exercise, unless there are furnaces and baths especially arranged for tempering tools.A second point to be noticed in hammers of this class is the nature of the connection with the driving power. In all cases there will be found an equivalent for the elastic helve of the trip-hammereither air cylinders, deflecting springs, or other yielding attachments,interposed between the crank and the hammer-head, also a slipping frictional belt or frictional clutches for driving, as in the case of trip-hammers.
The streets and squares where the high military officers had established themselves were closed by cordons of soldiers, and nobody was allowed to pass them.In making notes, as much as possible of what is written should be condensed into brief formul?, a form of expression which is fast becoming the written language of machine shops. Reading formul? is in a great degree a matter of habit, like studying mechanical drawings; that which at the beginning is a maze of complexity, after a time becomes intelligible and clear at a glance.
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