Page:Popular Science Monthly Volume 92.djvu/952

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��Popular Science Monthly

��the same numbered lines, then make a cross, connect these crosses with a free- hand curve and the one-quarter pattern is complete.

The illustration (Fig. 2) shows the meth- od of developing the pattern for a bath

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��A pattern for a bathtub is developed in a similar manner to a hopper and pipe

tub. Notice that the tub is made up of five parts, bottom, two ends and two sides. The pattern for the bottom needs no development as the top view, A, gives us a true pattern. The patterns for both ends and one side must be developed in exactly the same manner as that described for Fig. 1, and will not be repeated here. Notice that it is one-half of a cone and developed in the same manner as for the hopper and pipe.

The pattern for the end, C, is developed in the same manner, except that the base circle has been drawn downwards instead of upwards as was done on end view B. This method is often used and was intro- duced here so that the students of this series might become familiar with it. The base circle is divided and the points projected to the base line, then to the apex in the usual manner. The points where the radial lines from base to apex cross the curved line of the tub are pro- jected over to line apex-1 and then swing across the pattern until they cross the same numbered lines in exactly the same manner as described for previous prob- lems.

The pattern for the side, 1), is easily drawn. The correct width is obtained

��from D front view. The height is not correct on the front view because the top edge is leaning towards us. The correct height is obtained from the line, 1-X. It is the same height as the side, D, and has the same angle of inclination or slant, therefore, the line, 1-X, is the true height of the side, D. Set off the width from D and the height, 1-X, and the pattern for all parts is complete. Allowance must be made on these patterns for seams, and wiring as shown in previous issues.

The illustration (Fig. 3j shows the de- velopment of patterns for an "egg tester." A lighted candle is placed inside and the eggs are held against the egg- shaped hole. This must be done in a dark room. If the egg is clear and transparent it is fresh; if cloudy it is old. If it shows a dark spot, the process of incubation has started. The V-shaped hole at the bottom is to admit air so that the candle will burn brightly.

The technical description of the prob- lem would be "development of pattern for a cylinder intersecting a truncated cone." As stated before, these terms are often confusing to the non-technical reader, but advanatge should be taken of every opportunity to become familiar with them.

The development of the pattern for the round pipe (cylinder) has been described so many times in various ways in this series that no further description is deemed necessary, neither is it shown in the drawing. The best explanation will be found in the December, 1917, issue, "Development of Pattern for Tee Joints." The egg-shaped hole is drawn freehand.

The development of the pattern for the cone gives us an opportunity to review the use of auxiliary points and to make use of a still different method of drawing the bottom view and base line circle. The steps taken are as follows: First, draw front view A and side view B. Second, complete the cone by continuing the side lines until they meet at the "apex." Third, draw the bottom view, that is the circle on the base line. Notice that this is the first time that we have drawn the full circle on the base line. In previous issues it has been dropped down some distance from the front view to avoid confusion, but it is now time that we become acquainted with these different

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