Design of Piston

1
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
2
Review of last class(26-09-07)
Design of piston crown thickness Design of piston
rings
Today's topic
Design of piston pin Design of piston
land Distance Of first ring groove form top.
Problem On Design of Piston.
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
3
Design of Piston Rings
The depth of the piston ring (h) h 0.7 tr to
1.0 tr Equ. 18.28 a Pg. 363
The distance from top to the first groove (tg) tg
1.0 t1 to 1.2 t1 Equ. 18.30 Pg. 363
The lands between the ring grooves (tland) tland
h or slightly less than h (lth) Equ 18.31
Pg. 363
i No. of piston rings
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
4
The maximum thickness of the piston barrel
(t3) t3 0.03 D b 4.5 mm Equ. 18.20 Pg.
363 b depth of ring grooves.. mm tr
0.4 mm
The wall thickness towards the open end of the
piston (t4) t4 0.25 t3 to 0.35 t3
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
5
Diameter of the Pin

• Design of Piston pin
• Designed for maximum combustion pressure.
• It is usually hallow to reduce its weight.
• Center of the pin (0.02 D to 0.04 D) above the
  center of the
• skirt.
• The pin is considered as a simple beam uniformly
  loaded
• for a length which is in the connecting rod
  bearing with
• supports at the centers of the bosses at both
  ends.
• The bosses are at least 1.5d
• The length of the pin in the connecting rod
  bearing is
• about 0.45 D.

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
6
Problem.1Design of Piston
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
7
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
8
Step1 Calculation of Power

H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
9
Step 2 Calculation of Thickness
based on heat dissipation
192491 J/s-m2
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
10

2220C

A
K 460
11.78 mm 12mm
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
11
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
12
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
13
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
14

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
15
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
16

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
17
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
18

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
19
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
20

D100mm, t116mm t land3mm, h 3mm tg20mm,
t3 4mm L100mm, tr 4mm I4mm, d41mm
Piston dimensional nomenclature
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga
21
Piston pin
H.K. Govindaraju, Asst. Prof., SJM Institute of
Technology, Chitradurga