Problem 7.3 Section of Solids – A pentagonal pyramid, side of base 40 mm and height 80 mm is resting on H.P. on its base with one of the edges of the base away from V.P. is parallel to V.P. It is cut by an A.I.P. which is inclined at 600 with H.P. and passing 20 mm below the apex. Draw its elevation, sectional plan and true shape of section.
Step-1 Draw a horizontal x-y line of some suitable length.
Step-2 Draw a pentagon of side of base 40 mm below the x-y line at some suitable distance from it, such that the one of the sides of the pentagon should be parallel with x-y line and away from it. Then find the center point of the pentagon, and connect all the corners of the pentagon to the center of the pentagon by straight lines as shown in the figure. Give notations on it.
Step-3 From the center of the pentagon, draw a vertical center line of length 80 mm from the x-y line as shown into the figure. And from these notations of the pentagon draw vertical projectors up to x-y line, and then converge all these projectors at the end of the center line i.e. apex of the pentagon (point o’) as shown into the figure. It is a triangular shape. And Give the notations on it.
Step-4 Draw a cutting plane line passing at the distance 20 mm below the apex & on the center line of the cylinder in front view, such that its inclination with the x-y line should be equal to 60°, as shown into the figure.
Step-5 Give the cutting points name at the intersection of the previously drawn cutting plane line with the vertical projectors of the pentagon in front view, i.e., 1’, 2’, 3’ etc. as shown into the figure.
Step-6 From these points of intersections, draw vertical downward projectors in the top view such that these projectors will intersect with the respective lines in the top view. Now connects all these points in sequence by giving notations with straight lines, as shown in the figure. And draw hatching lines in the shape obtained. It is Sectional Top View.
Step-7 Now draw a line x’-y’, parallel with the cutting plane line in the front view, which should be outside of the boundary of the front view as shown into the figure. From the cutting points, i.e., 1’, 2’, 3’ etc., in the front view draw projectors which should be perpendicular to the cutting plane line and should be of some suitable length as shown into the figure.
Step-8 Now measure the distance of the cutting points from the x-y line, into the Sectional Top View and transfer the same at the respective projectors drawn from the cutting points in the front view, on the previously drawn x’-y’ line, which is parallel to the cutting plane line in the front view.
Step-9 Connects all the points in sequence with medium dark straight lines as shown in the figure, and draw hatching lines in it. It is the True Shape of the section.
Step-10 Give the dimensions by any one method of dimensions and give the notations as shown into the figure.