Design of Piston

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Govindaraju.H.K.Assistant Professor and
Head,Department of Automobile Engg.,S J M
Institute of Technology,Chitradurga 577
502.e-mail anchith_g_raj_at_yahoo.co.in Subject
Theory and Design of Automotive Engines
Sub Code - AU51V
Semester, Automobile Engineering
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Design of Piston
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
3
Problem No.1 Design a cast iron piston for
a 4-stroke single acting engine from the
following data. Cylinder bore dia 100 mm (D),
Stroke length 120 mm (L), Gas pressure 5
Mpa, (p) BMEP 0.5 MPa, Fuel consumption
0.15 Kg / BP (W) , Speed 2200 rpm. (N)
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Step1 Calculation of Power

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Step 2 Calculation of Thickness
based on heat dissipation
192491 J/s-m2
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
6

2220C

A
K 460
11.78 mm 12mm
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Step 3 The thickness of piston head based
on stress
0.43 x 100 x
15.597 mm 16 mm
Step4 The thickness head based on Empirical
Formula
4.8 mm
Step5Length of the piston (L)
L D , 100mm
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Step 6 Design of Piston Rings
Radial thickness
3.167 mm
Where D Bore dia. 100 mm Pr
Magnitude of radial pressure on the piston
rings 0.02746 N/mm2 (MPa) Table
18.6 Pg. 366 For petrol engines
Allowable stress for Cast Iron
82 to 100 N/mm2 82
N/mm2
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
9
Step 7 The depth of the piston ring (h)
h 0.7 tr to 1.0 tr Eq. 18.28 a Pg. 363
0.7 x tr 0.7 x 3.167 2.22 mm
Step 8The distance from top to the
first groove (tg) t g 1.0 t1 to 1.2 t2
Eq. 18.30 Pg. 363 1.2 t1
1.2 t1
1.2 x 16 19.2 mm
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
10

Step9The lands between the ring grooves
(tland) tland h or slightly less thanEq8.31
Pg. 363 h 2.22 mm
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Step 10 The minimum depth of the piston
ring Eq. 18.28b Pg. 363
i No. of piston rings 4 no.
Step11 The maximum thickness of the piston
barrel (t3) t3 0.03 D b 4.5
mm, Eq. 18.20 Pg. 363 b depth of
ring groove, mm tr 0.4 mm 3.169
0.4 3.57 mm
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
12

t3 0.03 x 100 3.57 4.5 11.07 mm
Step12The wall thickness towards the open end of
the piston (t4) t4 0.25 t3 to 0.35 t3
0.3 t3 0.3 x 11.07 3.321 mm
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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Step13 Stroke length (L5) L5 1.3 D to 1.4 D
Eq. 18.23 Pg. 363 1.3 D 1.3 x 100
130 mm
Step14 Diameter of the piston pin (d)
Eq. 18.24(Pg.362)
Gas pressure (P max) 5 MPa Bearing pressure
(Pb) 15.7MPa
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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l1 K1 d Length of the gudgeon pin
bearing in mm
K1 1.5 for petrol and gas engines 2 for
oil engines d Diameter of piston pin l1
1.5 d
40.83 mm
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
15
Step15 Force on piston (Fp) Fp P
x A
39.27 KN
d 40.83 mm
Step16 Check for strength of the piston pin
The bending stress of piston pin,
Fp Force on the piston, N Z Section modulus,
mm3
4.99 5 MPa lt 62 MPa for carbon steel
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
16
Courtesywww.technologystudent.com
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
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H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
18
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
19

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
20

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
21
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
22
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
23
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
24
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
25

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga