Mechanical Engineering M h i l E i i Drawing Drawing MECH - - PowerPoint PPT Presentation

M h i l E i i Mechanical Engineering Drawing Drawing MECH 211/M

• Lecture #8 Chapter 22

p

• Dr. John Cheung

Quiz - Intersection Quiz Intersection

• Complete the missing view and show the intersection of

p g two cylinders.

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Quiz - Intersection Quiz Intersection

• Missing view.

g

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Quiz - Intersection Quiz Intersection

• Intersection of two cylinders.

y

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Developments

• Construction of an unfolded or unrolled

surface of a form

• Commonly used in

Sheet metal Sheet metal Packaging / Containers

Pipes / ducts

Pipes / ducts Pattern making

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Developable Surfaces

Parallel edge Vertex

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Vertex

Sheet Metal Hems & Joints

Markings and foldings done from inside

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Parallel-Line Developments

• 1. Find T.S for base – use its perimeter

p as stretch-out line.

• 2. Seam line – shortest lateral edge
• 3. Top and bottom attached to longer

edge edge.

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Development of Oblique Prism

1 Fi d t l th f l t l

• 1. Find true length of lateral

edges.

• 2. Find true shape of section –

hence the stretch out line hence the stretch-out line.

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Development of Oblique Prism

1 Fi d t l th f

• 1. Find true length of

lateral edges.

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Development of Oblique Prism

Stretch-out line

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Development of Right Cylinder

• 1. Divide the cylinder periphery into

number of equal segments.

• 2. Base –stretch out line = 3.142 x Dia.

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Development of Oblique Cylinder – FIG-22-7

Both ends – Not TS

• 1. Find TL of lateral

edges.

• 2. Find true shape
• f cylinder cross

TS

• f cylinder cross

section.

• 3. Divide section

perimeter – number of segments.

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True length by revolution method True length by revolution method

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Development of a Pyramid – FIG 22-8

• 1. Point 0 located at base centre – use it

th t f l t l d di as the centre of lateral edge radius.

• 2. Top becomes true shape viewing perp.

to point views BC and AD. 3 Use revolution method to obtain TL

• 3. Use revolution method to obtain TL.
• 4. For line 0-3, Rotate line P3 about P0

to intersect horizontal line in TV. The intersection = 3R intersection 3R.

• 5. Project P3R to FV to intersect

horizontal line. Intersection = P3R in FV.

• 6. Line 0-3R = TL of Line 0-3.
• 7. Pyramid base = True shape, hence

edges = TL.

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Development of a Pyramid – FIG 22-8

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Development of oblique pyramid – FIG 22-9 Development of oblique pyramid FIG 22 9

• Use Point 0 as centre of

development.

• Use revolution method. If

i b t views become too messy, use True Length diagram.

• Pyramid base and top–

Pyramid base and top true shape, hence chord – true length.

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Development of oblique pyramid – FIG 22-9 Development of oblique pyramid FIG 22 9

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Development of right circular cone – Fig 22-10

• 1. Radial line developments.

p

• 2. S = Slant height, R = radius of

cone base.

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Development of oblique cone – Fig 22-11 Development of oblique cone Fig 22 11

• Find True length of cone base.
• Rotate Point 4 about

intersection between the slope and horizontal line to intersect horizontal line at P4’ in FV.

• Project P4’ to intersect the

horizontal line from P4 in TV at P4’.

• Repeat for others.
• Chord P4’-P5’ (R) = True

Chord P4 P5 (R) True

length for base from P4 to P5.

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Development of oblique cone – Fig 22-11 – T iti i Transition piece

• Extend contour elements –

Point A.

• Find TL of lateral edges.
• Line A-4 – Rotate P4 to

intersect horizontal line at P4” in TV.

• Project P4” to FV to intersect

j extended horizontal line from P4 – yielding corresponding P4”.

• Line A-P4” = True length of

Line A-4.

• Repeat method to cone top.

p p

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Development of oblique cone – Fig 22-11 – T iti i Transition piece

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Triangulation

• A process of dividing a surface into

triangles g

• Often used as an approximation
• Commonly used in transitional pieces
• Commonly used in transitional pieces

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Transition piece – Rectangular ends- FIG 22-13 a s t o p ece ecta gu a e ds G 3

• 1. Draw P9 and P10 to ease development.

2 Draw true length diagram One for lateral

• 2. Draw true length diagram. One for lateral

edges and other for diagonal lengths.

• 3. Base and top = True shape.
• 4. Chords in base and top – true length.

g

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Transition piece – Rectangular ends- FIG 22-13 a s t o p ece ecta gu a e ds G 3

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Transition piece connecting two circular d t FIG 22 14 ducts – FIG 22-14

• Elements do not intersect

at a common vertex.

• Circular intersection with

l i t h larger pipe – true shape in TV.

• Other end – true shape in

Other end true shape in Auxiliary view.

• Planes in cone not

ll l A i t parallel – Approximate development by triangulation method. g

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Transition piece connecting two circular d t FIG 22 14 ducts – FIG 22-14

• 1. TL diagram – edges.

2 TL diagram – diagonal

• 2. TL diagram

diagonal lines. Diagonal

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Edges

Square to Round Transition Square to Round Transition Piece

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In Class Assignment

• Page 661 Figure 22.20 Problem 2
• Using revolution method

Using revolution method.

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