Page 140 - Engineering drawing from first principles using AutoCAD

Three-dimensional projection exercises 133

Figure 6.11

In the second. example (Fig. 6.15) the square prism is inclined at an angle of 45° to the
base. The construction lines for the polygon ABDECare required to establish the points R
and S.
The projection exercise in Fig. 6.16 shows a hexagonal pyramid with a triangular
prism passing through its sides. Redraw the views shown, commencing with the plan
and the hexagonal base. The dotted hexagon will give the profile parallel to the base
and 25mm above the base. All the relevant construction lines are given. It is necessary
to establish all of the corner points in each view before drawing a pattern development
of the two parts.

In Fig. 6.17 a cone and sphere intersect and the exercise shows the method of drawing the
curve of interpenetration. Set out the cone and sphere to the given dimensions. With a
relatively small screen I find it beneficial to line in those parts of the outline which I know
will be needed in the final solution, as this procedure reduces the number of construction
lines on the drawing.