ONE:As a means for transmitting power, shafts afford the very important advantage that power can be easily taken off at any point throughout their length, by means of pulleys or gearing, also in forming a positive connection between the motive-power and machines, or between the different parts of machines. The capacity of shafts in resisting torsional strain is as [46] the cube of their diameter, and the amount of torsional deflection in shafts is as their length. The torsional capacity being based upon the diameter, often leads to the construction of what may be termed diminishing shafts, lines in which the diameter of the several sections are diminished as the distance from the driving power increases, and as the duty to be performed becomes less. This plan of arranging line shafting has been and is yet quite common, but certainly was never arrived at by careful observation. Almost every plan of construction has both advantages and disadvantages, and the best means of determining the excess of either, in any case, is to first arrive at all the conditions as near as possible, then form a "trial balance," putting the advantages on one side and the disadvantages on the other, and footing up the sums for comparison. Dealing with this matter of shafts of uniform diameter and shafts of varying diameter in this way, there may be found in favour of the latter plan a little saving of material and a slight reduction of friction as advantages. The saving of material relates only to first cost, because the expense of fitting is greater in constructing shafts when the diameters of the different pieces vary; the friction, considering that the same velocity throughout must be assumed, is scarcely worth estimating.
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
Aenean commodo.
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
Aenean commodo.
THREE:Die-cutting produces screws which may not be true, but are still sufficiently accurate for most uses, such as clamping and joining together the parts of machinery or other work.Our survey of Platos first period is now complete; and we have to enter on the far more arduous task of tracing out the circumstances, impulses, and ideas by which all the scattered materials of Greek life, Greek art, and Greek thought were shaped into a new system and stamped with the impress of an imperishable genius. At the threshold of this second period the personality of Plato himself emerges into greater distinctness, and we have to consider what part it played in an evolution where universal tendencies and individual leanings were inseparably combined.
THREE:Second.The manner of moulding and its expense, so far as determined by the patterns, which may be parted so as to be 'rammed up' on fallow boards or a level floor, or the patterns may be solid, and have to be bedded, as it is termed; pieces on the top may be made loose, or fastened on so as to 'cope off;' patterns may be well finished so as to draw clean, or rough so that a mould may require a great deal of time to dress up after a pattern is removed.If she could only gain time! If she could only manage to throw dust in the eyes of this man! She would ask no questions, because that would be only by way of making admissions. She must feel her way in the dark.
THREE:Bruce fell in with this suggestion, and sat down to lunch with what appetite he could. He was terribly disturbed and uneasy. He was dining that night with Countess Lalage, who was giving one of her brilliant little parties. There would be a chance of a cosy little chat with Hetty afterwards, but all the same as Bruce dressed he wished that he was not going.
