Piston PinPiston Pin

• Modern engines mainly use Modern engines mainly use Fully FloatingFully Floating Pins Pins

• Semi-FloatingSemi-Floating Pins are used to a limited extent Pins are used to a limited extent

Important ParametersImportant Parameters• Bending StressesBending Stresses• Shearing StressesShearing Stresses

• Stresses and Strains due to the Stresses and Strains due to the OvalizationOvalization of of the pinthe pin

Piston PinPiston Pin

• The Height and mass The Height and mass of a piston is of a piston is influenced by the influenced by the diameter of the diameter of the piston pinpiston pin

• Failure occurs due Failure occurs due Fatigue Fatigue stresses stresses arising from arising from ovalization and by ovalization and by tangential sheartangential shear

• Carburizing Carburizing increases the increases the endurance limit by endurance limit by 15 - 20 %15 - 20 %

• NitridingNitriding by 35 - 40 by 35 - 40 %%

Loading of the Piston PinLoading of the Piston Pin

Loading of the Piston PinLoading of the Piston Pin

d

DAverage value

rd

dAverage value

l

D

b

D

ex

dex

pp b

0 34 0 38 0 36

0 52 0 58 0 56

0 85 0 40

. . ( : . )

. . ( : . )

. .

int

Loading of the Piston PinLoading of the Piston Pin

The Following Forces are The Following Forces are consideredconsidered

•The maximum force due to The maximum force due to combustion (combustion ( > 360 ) and the > 360 ) and the inertia force toward TDC (inertia force toward TDC (<360)<360)

•Inertia forces at the end of the Inertia forces at the end of the exhaust stroke toward TDC exhaust stroke toward TDC ((<720)<720)

Checking Dimensions Checking Dimensions Against BendingAgainst Bending

mmpp= mass of piston assembly= mass of piston assembly

r = S/2 r = S/2 ’ = r/l l = Connecting rod length’ = r/l l = Connecting rod length

= Bending stress < 1.5 - 2.5 x 10= Bending stress < 1.5 - 2.5 x 1055 kN/m kN/m22

= radial velocity of the crankshaft (rad/s)= radial velocity of the crankshaft (rad/s)

kN10x1rmF

kNPD4

Fand

F7.0FFwherer12.1d

a5.1b2lF

3'2pi

max2

g

ig4d

3ex

bpp

Checking AgainstChecking AgainstPressure in Projection AreaPressure in Projection Area

a Piston Bosses

qF F

d l bx kN mb

g i

ex pp b

) :

.. .

0 70 2 0 4 105 2

b Connecting Rod Small End Bush

qF F

d ax kN mr

g i

ex

) :

.. .

0 70 25 0 5 105 2

Checking againstChecking againstTangential Shear StressTangential Shear Stress

0 85 0 7 1

10 8 1 0 10

2

45 2

. ( . )( ). .

F F r r

d rx kN m

g i d d

ex d