Cotter joint.msi

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1. DEPARMENT OF DIPLOMA MECHANICAL ENGINEERING PRESENTATION ON “ COTTER JOINT” Presentation By , Prof. Mayur S. Itankar Session : 2017-18 BALLARPUR INSTITUTE OF TECHNOLOGY, BALLARPUR

2. COTTER JOINT A cotter joint is used to connect rigidly two co-axial rods or bars which are subjected to axial tensile or compressive forces . It is a temporary fastening. A cotter is a flat wedge shaped piece of rectangular cross section and its width is tapered (either on one side or on both sides) from one end to another for an easy adjustment. . S o c k e t C o t t e r S p i g o t

3. APPLICATIONS OF COTTER 1. Connection of the piston rod with the cross heads Joining of tail rod with piston rod of a wet air pump Foundation bolt Connecting two halves of fly wheel (cotter and dowel arrangement)

4. Why taper is provided to cotter Taper is provided due to 2 reasons. When cotter is driven through the slots, it fit, fight due to wedge action. This ensures tightness of joint in operation and present loosening of the parts. Due to taper, it is easy to remove the cotter joint and dismantle the joint

5. Design of Spigot and Socket Cotter Let P = Load carried by the rods, d = Diameter of the rods, d1 = Outside diameter of socket, d2 = Diameter of spigot or inside diameter of socket, d3 = Outside diameter of spigot collar, t1 = Thickness of spigot collar, d4 = Diameter of socket collar, c = Thickness of socket collar, b = Mean width of cotter, t = Thickness of cotter, l = Length of cotter, a = Distance from the end of the slot to the end of rod, σ t = Permissible tensile stress for the rods material, τ = Permissible shear stress for the cotter material, and σ c = Permissible crushing stress for the cotter material.

6. 1. Design of rod i) Strength of rod considering tensile failure is given P = Area x Tensile stress

7. 2. Design of spigot –end i ) Considering failure of spigot under tension Area Resisting= P d 2

8. ii) Considering shearing failure of spigot

9. iii) Considering crushing of spigot end Resisting area(A)= d 2 x t P=d 2 x t x σ c d 2

10. 3. Design of spigot coller consdering shearing failure of spigot-collar

11. ii) Failure of spigot collar in crushing

12. 4. Design of socket i) Considering failure of socket under tension Area Resisting = Load P= .

13. ii) Considering shearing failure of socket

14. iii) Considering failure under crushing

15. 5. Failure of cotter in shear