Q18: A pentagonal pyramid of base side 30 mm and axis 60 mm is resting on a triangular face on the H.P. with its axis parallel to the V.P. It is cut by a plane whose H.T. is inclined at 30 to the reference line and bisects the axis such that the apex is removed. Draw its sectional front view and obtain the true shape of the section.
Solution:
Steps of construction :
- To draw the front view, the axis of the pyramid is made perpendicular to the xy line such that its base rests on H.P. Now, in this case, the pentagonal pyramid is resting on its base, therefore, its cross-section is visible in the top view. Hence top view is drawn first.
Top view: Pentagon of side 30 mm with one side perpendicular to VP.
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2. The front view is drawn with the help of all the points from the top view projects vertically upwards.
3. Section plane S1 S2 is drawn bisecting the axis at an angle of 30 such that its H.T. meets the reference line, thus generating points from 1 to 6 in the sectional top view.
4. The sectional front view is drawn by projecting all the points from 1 to 6, thus generating points from 1’ to 6’ in the sectional front view.
The true shape is drawn with the help of all the points from the sectional top view and sectional front view.
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