« НазадПродовжити »
subject of projection, that is, the making of working drawings, and we do not mean to scare
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 drawing.
It does not require any book knowledge to do the work either. A knowledge of plumbing, 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 mechanical 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
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 error is met with time and time again. As we have stated while considering the subject of projection, in mechanical 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.
the intention of the writer to 13, 14 and 15, give correct illustra-
at first, and growing more diffi- tional incorrect sketches showing ercult as the subject advances. Those who rors that are often made. Now as to layare following the series with the idea of ing out the work in Fig. 13, simply reusing the instruction given as a means member that the horizontal lines are to of learning how to make plumbing be made with the tee square as shown drawings, should lay out the – work in Chapter I, and the vertical lines by given, endeavoring to make it as nearly using the triangle against the tee square. like the model which we show as pos- We would say that in working out these
Fig. 13, Horizontal Lines to be made with T square
Fig. 14-Showing Correct and Incorrect Sketch
In laying out the Y, Fig. 14, notice that the branch is at 45 degrees with the length of the fitting, and consequently should be laid out with the 45 degree
exercises they should be done in pencil, and not inked, as that will be taken up later on. Since no inking is to be done, all lines should be made plain and not shaded with heavy lines as our sketches are made.
The shading is done to give character to an illustration and to set it out, and the method of doing it will be taken up under the subject of inking. In laying out the tee in Fig. 13, be careful to proportion the branch properly. Do not get it into the center of the fitting as the incorrect sketch shows, and do not have the branch loo long, as is also shown. Another point, a small one however, is the
Fig. 16-Curve in Lower Sketch Not Properly Drawn
triangle placed against the tee square.
Do not place the branch far down on the fitting as the incorrect sketch shows.
The hubs shown on the latter sketch do not give as good an appearance to the work as those in which a bead is shown at the top. Although the intersection of the branch and fitting is a curve, as shown, the method in the incorrect sketch answers as well, and is much easier. In drawing the strap, Fig. 15, draw in the straight parts of the trap first, and put in the curves next. Do not get the three branches of the trap too far apart, as shown in the incorrect sketches, and the middle part should the center to either of the lines, the curve neither be quite vertical, nor on too much of a slant. Speaking of the curves reminds us that a little instruction is needed on the proper manner of putting
Fig. 15 -Anuther Example of Correct and Incorrect
Work intersection of the branch with the main part of the fitting. Do not make it in the
rm a curve as the incorrect sketch shows, but with two 45 degree lines.
them in. If two lines at right angles to each other are to be joined by a curve, it is necessary to take the center for the curve at an equal distance from each
With the center taken at any point on this line, the two straight lines can be joined with a smooth curve, the curve being longer or shorter as the center is taken further from or nearer to the angle.
We are often required to put in curves joining lines which are at some odd angle as in Fig. 17. In this case it is more difficult to find a line of centers, and it is usual to keep trying one point after another until the right point for the center is found. In fact, draughtsmen seldom take the trouble to find a line for their center as Fig. 16 shows, but soon become so expert in finding by trial the right location from which to strike the curve, that they seldom need more than a couple attempts before obtaining the right point.
We have stated that our intention is to
Fig. 17—Showing How Curves are Put In, Joining
Lines at Odd Angles line, and from this point, with a distance on the compasses equal to that from will join both lines as the upper sketch in Fig. 16 shows.
A very common error in those just beginning the subject is to draw the curve as it appears in the lower sketch of Fig. 16, that is, so that it does not run smoothly into the straight lines, but leaves a corner at the point where the curve joins. Even though the center is taken so that it is equally distant from each line, this fault may occur by taking too long a radius on the compasses, a distance greater than the perpendicular distance from the center of the line.
The exact point for taking this center is on the 45-degree line from the angle made by the two lines, the dotted line in the sketch as illustrated on page 17.
Fig. 18—Sketch Obtained by Looking Down Into
the Sink give exercises for practice work. In addition to that we shall carry along the general subject of plumbing drawing as well.
There are two views which are neces