THREE:5. Every part laid down has something to govern it that may be termed a "base"some condition of function or position which, if understood, will suggest size, shape, and relation to other parts. By searching after a base for each and every part and detail, the draughtsman proceeds upon a regular system, continually maintaining a test of what is done. Every wheel, shaft, screw or piece of framing should be made with a clear view of the functions it has to fill, and there are, as before said, always reasons why such parts should be of a certain size, have such a speed of movement, or a certain amount of bearing surface, and so on. These reasons or conditions may be classed as expedient, important, or essential, and must be estimated accordingly. As claimed at the beginning, the designs of machines can only in a limited degree be determined by mathematical data. Leaving out all considerations of machine operation with which books have scarcely attempted to deal, we have only to refer to the element of strains to verify the general truth of the proposition.117
THREE:"Why should I?" Isidore asked coolly. "They came to me through a third party for value received, so that they are quite good. When these notes are presented the bank is bound to cash them. I'd give sixpence to know what is behind that queer, clever, ingenious brain of yours."Opening the throttle full-on, he kicked rudder and depressed his left wing. Around came the airplane. Skidding out of her course from the momentum and the sharp application of control, she moved sharply upward and sidewise.
THREE:
TWO:Referring first to the saving effected by combining several operations in one machine, there is perhaps not one constructor in twenty that ever stops to consider what is really gained, and perhaps not one purchaser in a hundred that does the same thing. The impression is, that when one machine performs two operations it saves a second machine. A remarkable example of this exists in the manufacture of combination machines in Europe for working wood, where it is common to find complicated [69] machines that will perform all the operations of a joiner's shop, but as a rule only one thing at a time, and usually in an inconvenient manner, each operation being hampered and interfered with by another; and in changing from one kind of work to another the adjustments and changes generally equal and sometimes exceed the work to be done. What is stranger still is, that such machines are purchased, when their cost often equals that of separate machines to perform the same work.