Jitendra Shah Feb 2012 Todays Class Sections of prisms Sections - PowerPoint PPT Presentation

Jitendra Shah Feb 2012

Today’s Class  Sections of prisms  Sections of pyramids  Sections of cylinders  Sections of cones  Sections of spheres

Because hidden lines are not enough to visualize internal details, often. By imagining removal of the portion between viewer and the cutting plane, the details can be better visualized (new terms: cutting plane, section plane) When projected on a plane parallel to section plane, the true shape of section is visible.

How to show section planes In the view where section plane is perpendicular to projection plane, you will see a line The way to show section plane is as in next figures : Chain , thin, thick at ends and also thick at change in directions When section planes are inclined to ref planes, projection on auxiliary planes needed to see true view How to show section lines Typically at 45 °. But when different materials and different parts variety of styles ( thickness and angles) used to differentiate parts or materials in section view of an assembly.

Sections of prisms 1.section plane parallel to V.P. Ex. A cube of 35 mm long edges resting on the H.P. on one of its faces with a vertical face inclined at 30 0 to the V.P. it is cut by a section plane parallel to the V.P. And at a distance of 10 mm from the axis of cube , on the side away from VP. Draw sectional front view and top view

1.section plane parallel to V.P. Solution – 1. Draw projections of cube in F.V. and T.V. c1 d1 b1 a1 X e g1 Y 1 f h1 1 30 0 d h g c a e f 35 mm b

Sections of prisms 1.section plane parallel to V.P. 2. Draw the section plane HT 10 mm from axis c1 d1 b1 a1 X e g1 Y 1 f h1 1 30 0 d h g c O a 10mm e T H f b 35mm

Sections of prisms 1.section plane parallel to V.P. 3. Project the points cut by plane and draw Section lines In a section view of c1 d1 b1 1 1 a1 2 1 machine elements no edges or dotted lines should be X e g1 Y shown. 1 f 3 1 h1 4 1 1 30 0 d h The dotted line in image on left is a g c mistake O a 10 mm e T H 1 2 3 4 f b

Sections of prisms 2.section plane perpendicular to H.P. & inclined to V.P. Ex. Same problem but section plane inclined 60 0 to V.P. 1.Draw projections in F.V. & T.V. 2. Draw the section plane HT 10 mm from axis inclined at 60 0 to V.P.

Section of prisms b1 c1 d1 a1 1. Draw projection of cube in TV and FV with its one face inclined at angle 30 X e g1 degree to VP Y 1 f h1 1 30 0 d H h g c O a e f b

Section of prisms b1 c1 d1 a1 2. Draw a section plane inclined at 60 degree to VP and 10 mm away from centre of cube X e g1 Y 1 f h1 60 0 1 30 0 d H h g c O a e f b 10 mm T

Sections of prisms 2.section plane perpendicular to H.P. & inclined to V.P. b1 c1 d1 a1 3. Draw new reference line X1Y1 parallel to HT (auxiliary vertical plane ) X e g1 Y Error in graphics as shown 1 f h1 60 0 here 1 30 0 X1 d H Do Not draw all edges as h final lines. Keep the boundaries as construction g c O lines. a e After sectioning , the removed edges will remain only as construction lines. 10 mm f b Y1

Sections of prisms 2.section plane perpendicular to H.P. & inclined to V.P. b1 c1 d1 1 1 a1 2 1 4. Draw the projections of section on the new plane(to get true shape) & on the F.V. 5. Draw section lines X e g1 3 1 4 1 Y 1 f h1 60 0 1 30 0 X1 d H h 3 1 g c O 3 11 a e 1 1 2 1 f 4 10 b mm 4 11 Y1 2 11

Sections of pyramids Ex. A square pyramid , base 40 mm side & axis 65 mm long has its base on H.P. and all the edges of the base equally inclined to the V.P. It is cut by a section plane, perpendicular to the V.P. , inclined at 45 0 to the H.P. & bisecting the axis . Draw its sectional top view , sectional side view & true shape of the section

Sections of pyramids  Solution 1. draw the projections of pyramid in required position o1 65mm x Y c1 b1 a1 d o a c 40mm b

Sections of pyramids 2.Draw line V-T 45 0 to X-Y bisecting the axis & then all sectional views. o1 T 3 2 1 3 1 4 4 1 2 32.5mm 1 1 1 X V Y 0 5 c1 4 b1 b a1 d d a 4 o 3 a c 1 2 b

Sections of pyramids 3.Draw line V-T 45 0 to X-Y bisecting the axis & then all sectional views and true shape 2 o1 3 True T shape 4 3 2 1 2 1 3 1 4 1 4 1 2 The width of true shape (2-4) can be measured in 1 1 1 X V Y Side view and placed 0 5 c1 4 b1 b in true shape a1 d d a 4 o 3 a c 1 2 b

Sections of cylinders  Ex. A cylinder of 40 mm diameter, 60 mm height & having its axis vertical , is cut by a section plane ,perpendicular to the V.P. , inclined at 45 0 to the H.P. and intersecting the axis 32 mm above the base. Draw its front view ,sectional top view ,sectional side view & true shape of the section.

Sections of cylinders  Solution- 1. Draw projections in F.V. ,T.V. and L.H.S.V 40 mm 60mm Y x Centre lines are a MUST In case of bodies of Revolution

Sections of cylinders 2.Draw sectional line VT . T 32mm X Y V 0 5 4 d 1 c 1 b 1 g a b c d 40 mm

Sections of cylinders 3. Complete the sectional views (the projections of section of circular should appear as ellipse in side view , right? It looks like a circle. Is there an error ? ) T g g 1 f 1 f 11 e 1 e 11 d 1 d 11 d 1 d c 1 c c 1 c 11 b 1 32mm b 1 b b 11 a 1 a X Y V 0 5 4 d 1 c 1 b 1 g a b c d

Sections of cylinders 4. Draw true shape in auxiliary plane g d 1 True c 1 shape b 1 T g g 1 d f 1 a f 11 c e 1 b e 11 d 1 d 11 d 1 d c 1 c c 1 c 11 b 1 Lines of symmetry b 1 b b 11 a 1 a MUST be shown X Y V 0 5 4 For circles and Elipses d 1 c 1 The chain lines must b 1 Extend beyond the g a body b c d

Sections of cones Ex. A cone , base 75 mm diameter & axis 80 mm long is resting on its base on the H.P. it is cut by a section plane perpendicular to the V.P., inclined at 45 0 to the H.P. & cutting the axis at a point 35 mm from the apex . Draw its F.V., sectional T.V. ,sectional side view & true shape of the section

Sections of cones  Solution- 1. Draw projections in F.V. ,T.V. and L.H.S.V 80m m X Y

Sections of cones 2.Draw sectional line VT & complete the sectional views (How do you get d1 and d in top view. Since the projector and generator coincide? In every other case, you can get an intersection T between projector and generator. Use circle method) f 1 g f e 1 e d 1 d c 1 c b 1 a 1 b X Y a 0 V 5 4 c 1 d 1 b 1 e 1 f 1 g a f b e d c

Sections of cones 3. Draw true shape in auxiliary plane e 1 f 1 g T d 1 c 1 f b 1 e d f 1 g f e 1 e a c d 1 d b c 1 c b 1 a 1 b X Y a 0 V 5 4 c 1 d 1 b 1 e 1 f 1 g a f b e d c

A cone , base 75mm dia, and axis 80 mm long is resting on its base on HP is cut by a plane perpendicular to VP, and parallel to and 12 mm away from one of its end generator. Draw its front view, sectional top view, true shape of the section (ref problem 14-24 , 14-25, N D Bhatt )

Draw cone and draw a section plane in FV Find the position of points on the section boundary and width of section at each point. How? Generator Method : draw generators and project intersection . Use rotation of the body to get otherwise difficult-to-locate points like on central generator Circle Method : e.g. In case of section plane parallel to base. You can get the width at any point by projecting on a circle in top view

Name the centre as O in TV and O' in FV Divide base circle (TV) in 12 parts. Draw generators. Number points from 1 to 12 in TV. Project the points on base line in FV and number them as 1' to 12' in FV Draw O'2' to cut section line at points namele b' and so on. Project these (b', c'..) on corresponding lines in TV. Symmetry around axis parallel to xy line. This gives section in TV How will you project the point where axis of the cone cuts the section line in FV (hint: use turn the cone, use end generator, drop projector, draw arc ...) True shape: ? Sectional View : ?

Thank You