Instead of rotating the whole pyramid, simply rotate
the line of the edge itself into the horizontal on a
conventional orthographic view. For example, in view
C, the line of an edge from apex to base, as it appears
in the top view, is used as the radius for an arc to the
horizontal The point of intersection of the arc with the
horizontal is projected to the front view. A true-length
line for that edge is drawn (view D).
The following steps for developing a truncated
pyramid are shown in figure 14-50. This is a transition
piece for connecting a large square pipe with a smaller
one. Normally, the square ends would end in square
collars, which also would be developed.
1. Draw the orthographic views, completing the
lines of the sides to the apex (view A).
2. Rotate the line of one edge in the top view to the
horizontal and project it to the front view (view
Figure 14-51.--Development of a truncated pentagonal
3. Draw an arc with a radius equal to the length of
pyramid with the upper corners cut by a slanting plane.
this true-length line, plus its extension to the
apex of the pyramid. Draw a second arc
defining the upper limit of the true-length line
To develop a truncated pentagonal pyramid, like
that shown in figure 14-51, follow the same general
4. Step off lengths along these arcs equal to the
steps. However, since one lateral edge appears in its
sides of the pyramid (view D).
true length in the front view, the limits of the other edges
can be projected onto the line of this edge to determine
5. Connect these points with the vertex, as shown
the true lengths. Measure the length of each edge.
in view D.
Transfer this measurement to the development.
Figure 14-52 shows the following steps in the
development of an offset transition piece. It is offset
Figure 14-52.--Development of an offset transition piece.
Figure 14-50.--Development of a truncated pyramid.