The auxiliary departments, if disposed about an erecting shop in the centre, should be so arranged that material which has to pass through two or more departments can do so in the order of the processes, and without having to cross the erecting shop. Casting, boring, planing, drilling, and fitting, for example, should follow each other, and the different departments be arranged accordingly; whenever a casting is moved twice over the same course, it shows fault of arrangement and useless expense. The same rule applies to all kinds of material.
A great share of the handling about an engineering establishment is avoided, if material can be stored and received on a higher level than the working floors; if, for instance, coal, iron, and sand is received from railway cars at an elevation sufficient to allow it to be deposited where it is stored by gravity, it is equivalent to saving the power and expense required to raise the material to such a height, or move it and pile it up, which amounts to the same thing in the end. It is not proposed to follow the details of shop arrangement, farther than to furnish a clue to some of the general principles that should be regarded in devising plans of arrangement. Such principles are much more to be relied upon than even experience in suggesting the arrangement of shops, because all experience must be gained in connection with special local conditions, which often warp and prejudice the judgment, and lead to error in forming plans under circumstances different from those where the experience was gained.
(1.) How may the arrangement of an establishment affect its earnings?—(2.) Why is the arrangement of engineering establishments generally irregular?—(3.) Why should an erecting shop be a base of arrangement in engineering establishments?—(4.) What are the principal materials consumed in engineering works?—(5.) Why is not special experience a safe guide in forming plans of shop arrangement?
CHAPTER XX.
GENERALISATION OF SHOP PROCESSES.
Having thus far treated of such general principles and facts connected with practical mechanics as might properly precede, and be of use in, the study of actual manipulation in a workshop, we come next to casting, forging, and finishing, with other details that involve manual as well as mental skill, and to which the term "processes" will apply.
As these shop processes or operations are more or less connected, and run one into the other, it will be necessary at the beginning to give a short summary of them, stating the general object of each, that may serve to render the detailed remarks more intelligible to the reader as he comes to them in their consecutive order.
Designing, or generating the plans of machinery, may be considered the leading element in engineering manufactures or machine construction, that one to which all others are subordinate, both in order and importance, and is that branch to which engineering knowledge is especially directed. Designing should consist, first, in assuming certain results, and, secondly, in conceiving of mechanical agents to produce these results. It comprehends the geometry of movements, the disposition and arrangement of material, the endurance of wearing surfaces, adjustments, symmetry; in short, all the conditions of machine operation and machine construction. This subject will be again treated of at more length in another section.
Draughting, or drawing, as it is more commonly called, is a means by which mental conceptions are conveyed from one person to another; it is the language of mechanics, and takes the place of words, which are insufficient to convey mechanical ideas in an intelligible manner.
Drawings represent and explain the machinery to which they relate as the symbols in algebra represent quantities, and in a degree admit of the same modifications and experiments to which the machinery itself could be subjected if it were already constructed. Drawings are also an important aid in developing designs or conceptions. It is impossible to conceive of, and retain in the mind, all the parts of a complicated machine, and their relation to each other, without some aid to fix the various ideas as they arise, and keep them in sight for comparison; like compiling statistics, the footings must be kept at hand for reference, and to determine the relation that one thing may bear to another.