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    Software name: appdown
    Software type: Microsoft Framwork

    size: 124MB


    Software instructions

      This object is attained in planing machines by the friction of the belts, which not only cushions the platen like a spring, but in being shifted opposes a gradually increasing resistance until the momentum is overcome and the motion reversed. By multiplying the movement of the platen with levers or other mechanism, and by reason of the movement that is attained by momentum after the driving power ceases to act, it is found practicable to have a platen 'shift its own belts,' a result that would never have been reached by theoretical deductions, and was no doubt discovered by experiment, like the automatic movement of engine valves is said to have been.(1.) Why is the effect produced different on the top and bottom of a piece when struck by a hammer?(2.) Why does not a compound hammer create jar and concussion?(3.) What would be a mechanical difficulty in presenting the material to such hammers?(4.) Which is most important, speed or weight, in the effect produced on the under side of pieces, when struck by single acting hammers?

      An interesting example in the use of belts for communicating power to movable machinery is furnished by the travelling cranes of Mr Ramsbottom, in the shops of the L. & N. W. Railway, at Crewe, England, where powerful travelling cranes receive both the lifting and traversing power by means of a cotton rope not more than three-fourths of an inch in diameter, which moves at a high velocity, the motion being reduced by means of tangent wheels and gearing to attain the force required in lifting heavy loads. Observing the operation of this machinery, a person not familiar with the relations between force and motion will be astonished at the effect produced by the small rope which communicates power to the machinery.

      1. Geometrical drawings consist in plans, elevations, and sections; plans being views on the top of the object in a horizontal plane; elevations, views on the sides of the object in vertical [88] planes; and sections, views taken on bisecting planes, at any angle through an object.The term gearing, which was once applied to wheels, shafts, and the general mechanism of mills and factories, has now in common use become restricted to tooth wheels, and is in this sense employed here. Gearing as a means of transmitting motion is employed when the movement of machines, or the parts of machines, must remain relatively the same, as in the case of the traversing screw of an engine lathewhen a heavy force is transmitted between shafts that are near to each other, or when shafts to be connected are arranged at angles with each other. This rule is of course not constant, except as to cases where positive relative motion has to be maintained. Noise, and the liability to sudden obstruction, may be reasons for not employing tooth wheels in many cases when the distance between and the position of shafts would render such a connection the most durable and cheap. Gearing under ordinary strain, within limited speed, and when other conditions admit of its use, is the cheapest and most durable mechanism for transmitting power; but the amount of gearing employed in machinery, especially in Europe, is no doubt far greater than it will be in future, when belts are better understood.

      Some hints will now be given relating to apprentice experience in a workshop, such matters being selected as are most likely to be of interest and use to a learner.That same evening many more houses were burned down, more particularly in Outre-Meuse, although no valid reason was given for that.

      A short time after the destruction I was even obliged to accept it for a whole week, as on the same day on which I arrived in Louvain for another visit there was renewed fighting round the town. The Belgians had advanced as far as Rotselair, where the next day they held their ground against overwhelmingly superior numbers; but at last they had to retire, leaving a great many dead behind. The Belgians had even got on to the road Tirlemont-Louvain, and blown up the railway line in two places.

      Separating machines, such as bolts and screens, which may be called a class, require no explanation. The employment of magnetic machines to separate iron and brass filings or shop waste, may be noted as a recent improvement of some importance.

      The most effectual means of securing a uniform effect from a tempering bath is by violent agitation, either of the bath or the piece; this also adds to the rapidity of cooling.When I was half way between Lige and the Netherland frontier, I noticed that the village of68 Vivignes was burning in various places. It is a beautiful spot, quite concealed between the green trees on the slope of the hills, west of the canal. And the finest and largest farms were exactly those ablaze. The fire crackled fiercely, roofs came down with a crash and a thud. Not a living being could be seen. From the windows of the burning houses small white flags hung, and they too were one by one destroyed by the fire. I counted forty-five farms that were burning, destroyed by the raging flames.


      2. The connection between the hammer drop and valve cannot be positive, but must be broken during the descent of the drop.


      This book does not attempt to give more than evidence of the truth. It does not claim to have14 literary distinction; I have not even tried to give it that stamp. By relating various events successively witnessed, which have no mutual connection, this would be very difficult.An apprentice in entering the workshop should avoid everything tending to an appearance of fastidiousness, either of manner or dress; nothing is more repulsive to workmen, and it may be added, nothing is more out of place in a machine shop than to divide one's time between the work and an attempt to keep clean. An effort to keep as neat as the nature of the work will admit is at all times right, but to dress in clothing not appropriate, or to allow a fear of grease to interfere with the performance of work, is sure to provoke derision.


      "To the inhabitants of the City of LouvainHe thought that it was sufficiently protected by the immense Red Cross flag, and the words written on the door by the Germans themselves: "Professor Noyons, Netherland physician, to be spared." But he had been mistaken. The soldiers did not respect anything, and had forced an entry into the house, wounded that servant, and then wrecked everything in the most scandalous manner. Beautiful large Japanese jars had been smashed to pieces, valuable furniture damaged by knocking and breaking large pieces out of it with rifles and bayonets. A fine carpet was burned, as well as many pieces of furniture. A hole was burned even in the floor.