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will be readily seen that these three views give every dimension that would be required in making the given object from drawings, that is, height, width and thickness.
In fact, the front and top views without the side view give all that is required.
In mechanical drawing, when the object is complicated, it often happens that three views must be given to thoroughly depict the work, but in plumbing, usually only the top view, or plan, and one elevation is required.
At this point it is well to state that many of our readers will no doubt have difficulty in thoroughly understanding what we have written on projection. To these we would say that even though at the outset the subject is not clear, it will become plainer as the subject advances, and that it should not be an obstacle to going on, for we shall soon deal with the subject in a way that will appeal to the plumber from a practical and not from a technical standpoint, such as the opening of a matter of this kind must be.
CHAPTER II N obtaining the views of an object, Fig. 8 shows, but if placed in some odd
that is, the projections, as they are position, such views as Fig. 9 shows will called in mechanical drawing, such have to be made.
as Fig. 7 shows in the preceding Either set of views shows the dimenarticle, it is not necessary that the sions of the object equally well, but Fig. object be placed in any particular posi- 8 is preferable, because simpler. It will tion when the views are taken. In be noticed that in which ever position the ninety-nine cases out of a hundred, how- object is placed, the two views or more ever, the object is supposed to be placed that are 'taken must be consistent. It in the position from which the views can would not do to combine the front view be most easily obtained, that is, directly of Fig. 8 with the top view of Fig. 9. facing the observer.
With these explanations we shall leave Suppose we consider, for instance, a the subject of projection as far as its short length of steel rod having six faces. technical points are concerned, though we
If the piece is placed so that it is may have to allude to it occasionally. In squarely in front of the person making writing this series, we thoroughly apprethe drawing, with a face fully exposed, ciate the fact that very few of our readers the front and top views would be such as in all probability, have ever taken up the
subject of projection, that is, the making of working drawings, and we do not mean to scare our readers into the thought that they have got to grind away at that part of the work before being able to take up the real plumbing draw ing.
It does not require any book knowledge to do the work either. A knowledge of plumbing, an eye to proportion, and some little skill are all that is required. The two latter qualifications naturally can be obtained only by practice, and to this end we would earnestly advise our
subject, such work appears very inferior.
It is often seen, however, hardly a sketch made at examinations, indeed, that does not testify to the work. To thoroughly illustrate our meaning, we show in Fig. 10 a combination of perspective and mechanical drawing, and in Fig. 11 the same work in which nothing but me chanical drawing is to be found.
We give also in Fig. 12 a drawing which is entirely perspective.
Comparing Figs. 11 and 12, either one is correct, and shows the work in a proper manner. However, perspective,
Figure 12—An Illustration of Perspective Drawing readers to practice making drawings as such as shown in Fig. 12, is much more we proceed with the subject, and after difficult drawing than the plain mechanihaving made them, to compare the same cal drawing of Fig. 11. with our sketches, and apply the criti- Therefore it would seem to the writer cisms, which we shall make from time that as Fig. 11 illustrates a style of work to time.
which is entirely acceptable in showing In starting into the subject of plumb- all that is necessary to be known about ing drawing, we wish to emphasize a the work, it should be chosen in preferfact which we have already tried to ence to perspective drawing, and accordmake clear, and that is that perspec- ingly hereafter in this series we shall tive drawings should never be com- confine themselves almost entirely to the bined with mechanical drawing, for to plain drawings. those that have any knowledge of the We may add that it is not once in a
hundred times that perspective drawing is required, though occasionally it is very valuable in showing work in its proper shape.
In Fig. 10, which illustrates the same piece of work as the other two sketches, we find the two classes of drawing combined, and the effect is poor.
It will be noticed that while a plain, mechanical view is given of the tub, the lavatory is shown entirely in perspective, and the water closet partly so.
The latter shows especially poor taste. A glance at the water closet will show that while the main part of the bowl is shown plain, the circular rim is shown in its perspective appearance instead of the manner shown in Fig. 11. If the upper part of the bowl is in perspective, the whole drawing should be, as shown in Fig. 12.
This erro. is met with time and time again. As we have stated while considering the subject of projection, in me. chanical drawing a view may be taken looking directly down onto the object, and another view may be taken by looking directly at the front of it, but in this branch of drawing, the two
views must never be run together, as they must have been to give the view of the water closet shown in Fig. 10. Another point to be observed in connection with the work shown in Fig. 10 is that, if the drawing is designed to show the work in perspective, to be consistent, the piping should be shown in perspective just as much as the lavatory is, and after the style in which the piping in Fig. 12 is drawn.
A fixture should never be drawn in perspective without making all the work connected with it to agree.
For instance, the trap, waste, and back air for the lavatory are shown plain, which is inconsistent with the appearance of the fixture itself. The back air pipe running straight up from the crown of the pipe looks as if it must break through the bowl and marble slab, while the lines which are dotted show that this pipe in reality runs behind the marble back.
It should be noted that when lines of pipe or, in fact, any part of the work is hidden behind anything it is customary to dot the lines instead of making them full. Thus in Fig. 12 the pipe that runs under the floor is shown dotted.