The document discusses cotter joints, which use a flat wedge-shaped piece of steel to connect two rods transmitting axial motion without rotation. Cotter joints can experience tensile or compressive forces and are used in connections like piston rods and valve rods. A typical cotter joint involves one rod fitting into a socket in another rod, with a cotter driven into slots in both parts to rigidly connect them. The document provides parameters for a cotter joint and examples of failures, but does not give the failure equations. It also provides an example problem to design a cotter joint supporting a load ranging from 30 kN in compression to tension.

1. COTTER JOINTS KNUCKLE JOINTS

2. CENTRIC & ECCENTRIC LOADING

4. COTTER JOINTS
A cotter is a flat wedge-shaped piece of
steelas shown in figure.
This is used to connect rigidly two rods
which transmit motion in the axial direction,
without rotation.
These joints may be subjected to tensile or
compressive forces along the axes of the
rods.
Examples of cotter joint connections are:
connection of piston rod to the crosshead of
a steam engine,valve rod and its stem etc.
A typicalcotter jointis as shown infigure.
One of the rods has a socket end into
which the other rod is inserted and the
cotter is driven into a slot, made in both the
socket andthe rod.

5. •Let P = Load carried by the rods,
•d = Diameter of the rods,
•d1 =Outsidediameter of socket,
•d2 = Diameter of spigotor inside
•diameter ofsocket,
•d3= Outsidediameter of spigot collar
,
•t1=Thicknessof spigot collar
•d4 = Diameter of socketcollar
,
•c=Thickness of socket collar
,
•b = Mean widthof cotter
,
•t=Thickness of cotter
,
•l= Length of cotter
,
•a = Distance from the end of the slot to the end of
rod,
•σt = Permissibletensilestress for the rods material,
•τ = Permissibleshear stress for the cotter material,
and
•σc = Permissiblecrushing stressfor the cotter

7.  REMIND THESE POINTS
A Cotter Joints Is A Flat Wedge Link Piece Of Steel Of Rectangular Cross
Section Which Is Inserted Through The Rods At High Angle To Their Axes .It
Is Uniform In Thickness But Tapering In Width , Generally On One Side
Only. Usually The Taper Is 1 In 30.
When A Special Arrangement Like A Set-screw Is Provided For Keeping
The Cotter From Slackening
Its Taper May Be As Large As 1 In 7. The End Of The Cotter Are Made
Narrow To Facilitate The Hammering For Fixing And Removing.
Cotter Joins Are Generally Use To Fasten Rigidly Two Rod S Which Is
Subjected To Tensile Or Compressive Stress Along Their Axes. This Joint Is
Used To Connect Two Circular Rods.
This Joint In Not Suitable Where The Member Are Subjected Under
Rotation.

8. FAILURES :-

9. FAILURESCONTINUE...

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15. DIAGRAM FOR FAILURES

16. HERE ISTHE EQUATIONS OF FAILURES

17. Example 1: Design and draw a cotter joint to support a load varying from 30 kN in
compression to 30 kN in tension. The material used is carbon steel for which the following
allowable stresses may be used. The load is applied statically. Tensile stress = compressive
stress = 50 MPa ; shear stress = 35 MPa and crushing stress
Solution. Given : P = 30 kN = 30 × 103 N ; st = 50 MPa = 50 N / mm2 ; t = 35 MPa = 35 N /
mm2 ; sc = 90 MPa = 90 N/mm2