Machine Design Databook Episode 3 part 6 ppsx

The bending stress present in the case of slotted oil

control ring of rectangular cross section in terms of

tangential load, F

The tangential load or force required for opening of a

rectangular cross-section piston ringa

The piston ring parameter (k) in terms of tangential

load F
for rectangular cross-section rings

The tangential load or force required for opening of

rectangular cross-section slotted oil control rings

The piston ring parameter (k) in terms of free ring gap

(

f) for rectangular cross-section slotted oil rings for

use in Eq. (24-142g)

The piston ring parameter (k) in terms of the constant

pressure ( p) for rectangular cross-section rings also

for use in Eqs. (24-142f ) and (24-142g)

The radial thickness of the ring at a section which

makes an angle  measured from the center line of

the gap of the ring

Is ¼ moment of inertia of the slotted cross-section

ring, mm4

lco ¼ twice the diameter between center of gravity and

outside diameter, mm

bso ¼ 6ðd
hÞlcoIm

wh3Is

F
ð24-142dÞ

where bso in N/mm2

; F
in N; lco, d, h, and w in mm;

Im and Is in mm4

;max ¼ hE

d
h

ð1:26"T
1:84k þ 0:025Þ

SI ð24-142eÞ

where

"T ¼ d þ h

d
h
1

k ¼ piston ring parameter from Eq. (24-142f ) and

(24-142h)

k ¼ 3ðd
hÞ

2

wh3

F

E ð24-142fÞ

;maxT ¼ lciE

d
h

ð1:26"T
1:84k þ 0:025Þ

Im

Is

ð24-142gÞ

where

"T ¼ d þ h

d
h
1 SI

lci ¼ twice the distance between center of gravity and

inside diameter, mm

k ¼ piston ring parameter from Eq. (24-142e) and

(24-142f )

k ¼ 2

3

f

d
h ð24-142hÞ

k ¼ 3

2

p

E

dðd
hÞ

2

h3 ð24-142iÞ

h ¼ 3

ffiffiffiffiffiffiffiffiffiffiffi

24pr4

E

s

sin2 

2 ð24-142jÞ

Particular Formula

a Goetze AG, Piston Ring Manual, 3rd ed., Burscheid, Germany, 1987.

MISCELLANEOUS MACHINE ELEMENTS 24.41

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The maximum thickness of the ring which occur

opposite the gap of the ring (i.e., at  ¼ )

For piston ring dimensional deviation, hardness, and

minimum wall pressure

For cylinder bore diameter

hmax ¼

ffiffiffiffiffiffiffiffiffiffiffi

24pr4

E

s

ð24-142kÞ

Refer to Tables 24-7 to 24-9.

Refer to Table 24-10.

Particular Formula

TABLE 24-5

Values of c for various inclinations of coned pistons

Inclination ranges,

Cone
, deg c

— 0–6 1

Slightly 6–18 0.85–0.95

Medium 18–28 0.75–0.85

Strong 28–35 0.65–0.75

TABLE 24-6

Values of coefficient K for pistons (admissible pressures, kgf/mm2 absolute)

Pressure, kgf/mm2

Diameter of

cylinder, mm 0.01 to 0.02 0.02 to 0.04 0.04 to 0.06 0.06 to 0.08 0.08 to 0.10 0.10 to 0.12 0.12 to 0.14 0.14 to 0.16

380–575 1.000 1.125 1.375 1.500 1.750 2.000 2.125 2.500

575–775 1.375 1.500 1.750 2.000 2.500 2.750 3.000 3.375

775–975 1.500 1.750 2.000 2.500 3.125 3.500 3.750 4.000

975–1175 1.750 2.000 2.375 3.000 3.500 4.000 4.500

1175–1375 2.000 2.250 2.750 3.125 3.750 4.125

1375–1575 2.375 2.500 3.125 3.500 4.000 4.375

1575–1775 2.500 3.000 3.375 4.000 4.375

1775–1975 2.750 3.125 3.500 4.125

1975–2150 3.000 3.375 3.750 4.375

2150–2350 3.000 3.500 4.000

2350–2550 3.125 3.500

2550–2750 3.375 3.750

Key: 1 kgf/mm2 ¼ 1:42247 kpsi; 1 kpsi ¼ 6:894757 MPa.

24.42 CHAPTER TWENTY-FOUR

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TABLE 24-7

Recommended hardness for piston rings of IC engines

Nominal diameter, d, mm Hardness HRD

<100 95–107

100–200 93–105

>200 90–102

TABLE 24-8

Minimum wall pressure for piston rings of IC engines

Compression rings Oil rings

MPa kgf/cm2 MPa kgf/cm2

Petrola 0.059 0.60 0.137 1.40

Diesel 0.013 1.05 0.196 2.00

a Gasoline.

TABLE 24-9

Permissible deviation on the dimensions of piston rings

of IC engines

Dimensions Deviations, mm

Axial width, b
0.010

0.022

Radial thickness

80 mm ring diameter 0.08

>80 mm with 175 mm ring diameter 0.12

175 mm ring diameter 0.15

Parallelism of sides—40% of tolerance

on axial width

TABLE 24-10A

Preferred cylinder bore diameters for internal-combustion (IC) engines (all dimensions in mm)

30 (62) 95 125 (152.4) (188) (241.3) 315

32 65 98 (127) 155 190 (245) (317.5)

34 (68) (98.4) (128) (158) (190.5) (250) 320

(35) 70 100 (128.2) (158.8) (192) (254) (325)

36 (72) (101.6) 130 160 195 (255) 330

38 (73) (102) (132) (162) (196.8) 266 (335)

40 74 (103.2) (133.4) 165 198 (265) 340

42 (76) (104.8) 135 (165.1) 200 270 (343)

44 (78) 105 (138) (168) (205) (273) (345)

46 (79.4) 108 (139.7) 170 (209.6) (275) 350

48 80 110 140 (171.4) 210 280

50 82 (111.1) (142) (172) (215) (285)

52 85 112 142.9 175 (215.9) 290

54 87.3 (114.3) (145) (177.8) 220 (292.1)

56 88 115 (146) (178) (225) (295)

(57) (88.9) (118) (148) 180 (228.6) (298.4)

58 90 120 (149.9) (182) 230 300

(59) (91.4) (120.6) 150 (184.2) (235) (305)

60 (92) (122) (152) 185 240 103

MISCELLANEOUS MACHINE ELEMENTS 24.43

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TABLE 24-10B

Chemical composition of alloys and physical properties of aluminum alloy piston (values in % maximum unless shown otherwise)

Physical propertiesb

Coefficient

Tensile strength of thermal

expansion

Alloy Chill casting Forging (20 to 2008C)

designationa Chemical composition, %

Hardness, mm/mm/

Casting Forging Cu Mg Si Fe Mn Nic Zn Ti So Pb Cr Al

HB MPa kpsi MPa kpsi 8C 10
4

2285 34,850 3.5–4.5 1.2–1.8 0.6 0.7 0.2 1.1–2.3 0.2 0.23 0.05 0.05 90–130 225–275 32.7–39.8 345–410 49.8–59.7 23–24

4658 49,582 0.8–1.5 0.8–1.3 11.0–13.0 0.8 0.2 1.5 0.35 0.2 0.05 0.05 90–140 195–245 28.5–35.6 295–365 42.7–52.6 20.5–21.5

4928A 49,285 0.8–1.5 0.8–1.3 17.0–19.0 0.7 0.2 0.8–1.3 0.2 0.2 0.05 0.05 90–125 175–215 25.6–31.3 225–295 32.7–28.5 18.5–19.5

4928B 0.8–1.5 2.8–1.3 23.0–26.0 0.7 0.2 0.1–1.3 0.2 0.2 0.05 0.05 0.3–0.6

Remainder 90–125 165–205 24.2–29.7 17–18

a Alloys have been designated in accordance with IS 6051, 1970. Code for designation of aluminum and aluminum alloys.

b Physical properties are attainable after suitable heat treatment.

c The purchaser may specify nickel content, if so desired.

Source: Bureau of Indian Standards, New Delhi.

24.44

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