1. Engineering Graphics 2018-19-I
Lecture 26
TA101A
Engineering Graphics I By
Dr. Mukesh Sharma
Professor
DEPARTMENT OF CIVIL ENGINEERING
INDIAN INSTITUTE OF TECHNOLOGY KANPUR
KANPUR , INDIA

2. Development of an Oblique Pyramid
Seam line O1 Cr Dr A1 Or
Bend line Br Ar D1 B1 Or
Stretchout or girth C1
Axis
BRCR
AR,DR
Soldered lap seam
CRBR
ARDR

3. Development of Truncated Cone10 11 9 10 8 9 11 12 7 1I 8 12 6
R’T TI RI AT SI 7T 1T 5 ST 4 6 2 3 TI 5 3 4 AI AF RI 2 SI 1I TR RR RF SF 7F
3,11
2,12 IF
Development of Truncated Cone
This is called method of Triangulation – for Cone equal lengths triangle

4. YH X
Path of
Revolution XH
YHR
Axis H F XF F ӨR Y O TL YR H
TL Axis ӨH YF
YFR
OBSERVATION
If axis is perpendicular to the plane, the hypotenuse of triangle like XOYR will
always give the TL of the line. Or, if perpendicular and base are known so is the TL
Base is seen in the TV. Eureka moment in TA101!!

5. Development of Oblique Cone – Elements are of different lengths
One half of development OI CI 1I
10T CT
OT,DT 2I 9T 1T 3I 2T 4I 8T OF O 3T 7T 5I 4T 5T 6T 6I 7I 8I 9I
10I
True lengths CF 1F 3F 5F 7F 9F 10 DF D 9 7 5 3 1 C
Which line is seen in TL? O-10 in FV – begin development by laying off O-10
Is 10-9 seen in TL, if yes proceed and mark and arc.
Do we know TL of O-9? No we don’t.
In fact, no other element is in TL (except O-C). Find a smart way to find all lines in TL.
Recall if true altitude and base of line are known hypotenuse is the TL of line.
For line O-9 see altitude and base (in TV) and get TL.
Repeat the process for all lines and find TL diagram that gives all TLs.

6. Transition Pieces Connect two hollow objects having different base
Three surface
Transition Pieces
Triangulation Method: Dividing a surface into a number of triangles and transfer them to the development

7. Development of Transition Piece – Join Cylindrical Pipe to Rectangular PipeB’ D’
lower part A’ E C’ VI C A 1
9,P B’ B 2 8 3 7 1I 2 B 4 5 6 3
½ E D’ 4 5 D
½ E P C 6 7 OT VT
upper part 8 O V 9I OF
VF,P 3 42 51 7
5,8 9
For cone – B
(TL)
For cone – D
(TL)
The piece is composed of:
4-triangular planes (bases are sides of rectangle) (b) 4-parts of oblique cone (bases are arc of circles)
Development of Cone – Triangulation method – divide the cone in parts
Make true length diagram for each cone

9. Have a great Diwali!!
Cheers!!
God bless you all.