1 DESIGN OF COTTER JOINT 1.INTRODUCTION Socket and spigot cotter joint is used to connect circular rods. One of the rods is formed into a socket by enlarging its end while the other rod, called spigot end is formed with enlarged diameter and an integral collar. The spigot is put inside the socket and the cotter is driven through the slots in socket and spigot ends. A pictorial view of socket and spigot cotter joint . While a sectional view of socket and spigot cotter joint 2.AIM To find out the cotter joint dimensions and check its safe. For load P=5x10 3 N of load. Design cotter joint and calculate all the dimensions 3.SELECTION OF MATERIALS The material is selected for the given load criteria. So the material to be selected as plain carbon steel of grade 30c8 The maximum load s =400 N/mm 2 4.CALCULATION OF PERMISSIBLE STRESSES Assume factor of safety of spigot and socket is 6 For cotter is 4 4.1 For spigot and cotter Allowable stress in tension σ t =S t /6
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1
DESIGN OF COTTER JOINT
1.INTRODUCTION
Socket and spigot cotter joint is used to connect
circular rods. One of the rods is formed into a socket by enlarging its end while the
other rod, called spigot end is formed with enlarged diameter and an integral collar.
The spigot is put inside the socket and the cotter is driven through the slots in
socket and spigot ends. A pictorial view of socket and spigot cotter joint . While a
sectional view of socket and spigot cotter joint
2.AIM
To find out the cotter joint dimensions and check its safe.
For load P=5x103 N of load. Design cotter joint and calculate all the
dimensions
3.SELECTION OF MATERIALS
The material is selected for the given load criteria. So the
material to be selected as plain carbon steel of grade 30c8
The maximum load s =400 N/mm2
4.CALCULATION OF PERMISSIBLE STRESSES
Assume factor of safety of spigot and socket is 6
For cotter is 4
4.1 For spigot and cotter
Allowable stress in tension σt=St/6
2
=400/6=66.67N/mm2
Allowable stress in compression σc=2x400/6
=133.33 N/mm2
Allowable shear stress τ =0.5x400/6
=33.33 N/mm2
4.2 For cotter
Allowable stress in tension σt=St/6
=400/4=100 N/mm2
Allowable shear stress τ =0.5x400/6
=50 N/mm2
5.CALCULATION OF DIMENSIONS
5.1 Diameter Of Rods
𝑑 = 4𝑝
𝜋σt
𝑑 = 4𝑥50𝑥10𝑥10𝑥10
𝜋x66.67
3
d=30.9=31
5.2 Thickness Of Cotter
t=0.31d
=0.31x31=9.6=10
5.3 Daimeter Of Spigot
𝑃 = (𝜋
4 d2
2 - d2t) σt
𝑃 = (𝜋
4 d2
2 - d2x10)x66.67
d22-12.73d=954.88
d2=37.9=40
5.4 Outer Diameter Of Socket
𝑃 =𝜋
4((d1
2- d2
2)-(d1-d2)t) x σt
𝑃 =𝜋
4(d1
2- 40
2)-(d1-40)10)x66.67
d12-12.73d1-2045.59=0
4
d1=52.04
d1=52
5.5 Diameter Of Spigot Collar d3 And Socket Collar d4
d3=1.5d
=1.5x31
=46.5=48
d4=2.4d
=2.4x31
=7.4=80
5.6 Dimensions a And c
a=c=0.75d
=0.75x31
=23.25
a=c=24
5.7 Width Of Cotter
b=𝑝
2𝑡𝜏
b=50𝑥10𝑥10𝑥10
2𝑥50𝑥10
5
b=50mm
5.8 Thickness Of Spigot Collar
t1=0.45d
=15mm
6.SAFE CHECK FOR SPIGOT END
Stress in compression σc=𝑝
𝑡𝑑2
σc=50𝑥10𝑥10𝑥10
10𝑥40
=125 N/mm2<133.33 N/mm
2
Shear stress τ= 𝑝
2𝑥𝑎𝑥𝑑 2
τ= 50𝑥10𝑥10𝑥10
2𝑥24𝑥40
=26.04 N/mm2< 33.33 N/mm
2
Deign is safe
7. SAFE CHECK FOR SOCKET END
Stress in compression σc=𝑝
(𝑑4−𝑑2)𝑡
σc=50𝑥10𝑥10𝑥10
(80−40)10
6
=125 N/mm2<133.33 N/mm
2
Shear stress τ=𝑝
2 𝑑4−𝑑2 𝑐
τ=50𝑥10𝑥10𝑥10
2 80−40 24
=26.04 N/mm2<33.33 N/mm
2
Deign is safe.
8.AUTOLISP PROGRAM
(defun c:one ()
;P (getreal "enter the maximum load in N:")
;σt σc τ (getreal "enter the allowable stresses for spigot and socket in
N/mm^2 :")
;σt σc τ (getreal "enter the allowable stresses for cotter in N/mm^2 :")
;d (getreal "enter the diameter of rods in mm:")
;t (getreal "enter the thickness of cotter in mm:")
;d2 (getreal "enter the diameter of spigot in mm:")
;d1 (getreal "enter the outer diameter of socket in mm:")
;d3 d4 (getreal "enter the diameter of spigot collar and socket collar in