This was a question on drawing the plan view of the frustum of a pyramid, the true shape and the development. 

Many candidates attempted this question and were able to do the following:

-           draw the given elevation;
-           draw the plan;
-           true shape of the cut surface;
-           surface development.

However, they could not do the following:

-           complete the plan;
-           hatch the cut surface on plan;
-           transfer vertical coordinates from cut surface on the plan to locate points on the true shape;
-           join points and draw the true shape;
-           locate the base length on the circumference and joining to the apex;
-           locate the points of the cut surface and joining points to get the development of the truncated pyramid.

Candidates were expected to  the following:

TRUNCATED HEXAGONAL PYRAMID

A.         FOR DRAWING THE GIVEN ELEVATION

1. draw the hexagon on plan;
2. join the diagonal;
3. project up to draw the given elevation;
4. draw the cutting plane at 30º ;
5. draw the elevation.

 

B.         COMPLETING THE PLAN

1. project down from cut surface on the elevation to plan;
2. locate and complete the plan;
3. hatch the cut surface on plan.

 

C.        TRUE SHAPE OF THE CUT SURFACE

1. project perpendicular lines from the cut surface on the elevation;
2. draw reference line parallel to the cutting plane;
3. transfer vertical coordinates from cut surface on the pla to locate points of the true shape;
4. join the points and draw the true shape;
5. hatch the cut surface.

 

 

 

1. SURFACE DEVELOPMENT

1. draw lines from cut surface parallel to the base
2. draw radial lines for development
3. locate the base lengths on the circumference and join to the apex
4. locate points of the cut surface
5. join points to get the development of the truncated pyramid
6. draw the base.   

 

The solution is shown below: