Design of Cotter Joint New-BELWIN

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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

mm:")

;a c (getreal "enter the dimensions mm:")

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;b (getreal "enter the width in mm:")

;

(get command

;σt (St/fos)

;σc (*2st/fos)

;τ (*0.5st/fos)

;d sqrt (4p/πσt )

;t (0.31d)

;d2 (*/π/4 d22 -d2t σt)

;d1 (*/- π/4 d12- d22 d1-d2 tσt)

;d3 (* 1.5d)

;d4 (*2.4d)

;a c (* .75d)

;b (/ p 2Tt)

;t1 (* .45d)

(setq pt1 (polar pt1 (*.75d len))

(setq pt2 (polar pt1 0 (/p * 2tτ len))

pt3 (polar pt2 (* 2.4d len))

pt4 (polar pt3 (* .75d len))

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;----------------------------------------------------------------------------------------

pt5 (polar pt4 (90 .75d))


pt7 (polar pt6 0 (/ len 4))


;-----------------------------------------------------------------------------------------

pt9 (polar pt8 0 (90 .75d len))

pt10 (polar pt9 (* 2.4d * 2.5 len))


pt12 (polar pt11 (* .75d /p* 2Tt len))

;-----------------------------------------------------------------------------------------

pt13 (polar / pt1 pt2 (/4p * πσt len))

pt14 (polar pt13 0 ( 90 +d len))

pt15 (polar pt3 pt4 (/ b len)) (* 1 len))

pt16 (polar pt15 0 (+ 25 len))

;-----------------------------------------------------------------------------------------

pt17 (polar pt16 90 (+ 100 len))

pt18 (polar pt17 (*1.25 b len))

)

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;(command "pline" pt1 pt2 pt3 pt4 pt5 "")

;(command "pline" "pt6 90^" "" "pt7" "" "")

;(command "copy" "pt8 pt9" "" "pt3 pt4" "" "")

;(command "pline" pt10 pt11 pt12 "c")

;(command "pline" pt13 pt14 = pt1 pt2 "")

;(command "pline" pt15 pt16 pt17 pt18 "")

;(command "pline" pt15 pt16 = pt17 pt18 "")

;(command "line" pt18 "")

;(command "array" "last" "" "r" "1" "90^" "")

)

(defun

)

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9. 2D AUTOCAD DRAWING

Fig 9.1 2d Drawing

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10.COMMAND HISTORY FOR AUTOCAD

0.0000)

Specify next point or [Close/Undo]:

Specify next point or [Close/Undo]: *Cancel*

Command:

Command: _.erase 1 found

Command: _line Specify first point:

Specify next point or [Undo]:

Command:


Specify next point or [Undo]: 24








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Specify next point or [Undo]: *Cancel*

Command: <Ortho off>






Automatic save to C:\Users\sen\AppData\Local\Temp\Drawing1_1_1_0041.sv$ ...






Command: _qsave





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Command: '_zoom

Specify corner of window, enter a scale factor (nX or nXP), or

[All/Center/Dynamic/Extents/Previous/Scale/Window/Object] <real time>:

Press ESC or ENTER to exit, or right-click to display shortcut menu.










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Specify next point or [Undo]: <Ortho on>








Command: _trim

Current settings: Projection=UCS, Edge=None

Select cutting edges ...

Select objects or <select all>: 1 found

Select objects: *Cancel*


Command: Specify opposite corner:



Command: _trim


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Select cutting edges ... 1 found

Select object to trim or shift-select to extend or

[Fence/Crossing/Project/Edge/eRase/Undo]: *Cancel*

Command: _trim



Select objects or <select all>: 1 found

Select objects: 1 found, 2 total

Command: Specify opposite corner:

Command:

TRIM



Select objects or <select all>: *Cancel*

Command: _qsave

Command: '_zoom

Command: *Cancel*



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Command: _qsave

11. CONCLUSION

Thus the spigot cotter joint is designed and its calculations of dimensions are

obtained and the autolisp program is written to its design.

Design of Cotter Joint New-BELWIN

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