Figure 8-10.—Development of an oblique pyramid by triangulation.Right PyramidConstruct a radial-line development of a trianglewith a true length-of-edge line (fig. 8-9) and a rightpyramid having all the lateral edges (from vertex to thebase) of equal length. Since the true length of the lateraledges is shown in the front view (line (0-1 or 0-3) andthe top view shows the true lengths of the edges of thebase (lines 1-2, 2-3, and so on), the development maybe constructed as follows:With 0 as center (corresponding to the apex) andwith a radius equal to the true length of the lateral edges(line 0-1 in the front view), draw an arc as shown. Dropa perpendicular line from 0 to intersect the arc at point3. With a radius equal to the length of the edge of thebase (line 1-2 on the top view), start at point 3 and stepoff the distances 3-2, 2-1, 3-4, and 4-1 on the large arc.Join these points with straight lines. Then connect thepoints to point 0 by a straight line to complete thedevelopment. Lines 0-2, 0-3, and 0-4 are the fold lineson which the development is folded to shape thepyramid The base and seam allowance have beenomitted for clarity.Oblique PyramidThe oblique pyramid in figure 8-10 has all its lateraledges of unequal length. The true length of each of theseedges must first be found as shown in the true-lengthdiagram. The development may now be constructed asfollows:Lay out base line 1-2 in the development view equalin length to base line 1-2 found in the top view. Withpoint 1 as center and a radius equal in length to line 0-1in the true diagram, swing an arc. With point 2 as centerand a radius equal in length to line 0-2 in the true-lengthdiagram, swing an arc intersecting the first arc at 0. Withpoint 0 as center and a radius equal in length to line 0-3in the true-length diagram, swing an arc. With point 2as center and radius equal in length to base line 2-3 foundin the top view, swing an arc intersecting the first arc atpoint 3. Locate points 4 and 1 in a similar manner, andjoin those points, as shown, with straight lines. The baseand seam lines have been omitted on the developmentdrawing.Truncated PyramidFigure 8-11 shows a truncated pyramid that isdeveloped in the following manner: Look at the viewsin figure 8-11 as you read the explanation.Draw the orthographic views, extending the lines ofthe sides to the apex at the top in view A. Draw threehorizontal construction lines on the right side of theorthographic view (view B), one from the center of thetop view; one from the top of the front view; and onefrom the bottom of the front view. With the point of thecompass in the center of the top view, scribe two arcs(view C). Draw one from the inside corner of the topview to the horizontal line (point W), and the other fromthe outside corner of the top view to the horizontal line(point X). Draw two vertical lines, one from point W in8-7

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