Knucle Joints

8/3/2019 Knucle Joints

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Ismail Akbani

Assistant Professor Mechanical Engineering

Symbiosis Institute

of Technology,Pune





Biological Inspiration!!



Inspired???

Hope U are NOT…



How About this…………??? *

*After the Lecture Offcourse!!



Just

KNUCKLE KNUCKLE KNUCKLE KNUCKLE down for an hour or so….



Wake Up From Dreams!!!

• Used to connect tworods under tensile

load.

• Permits angular

misalignment of the

rods and may takecompressive load if

it is guided.



Knuckle JoinS???Two or more rods subjected to tensile and

compressive forces are fastened together Their axes are not

in alignments but

meet in a point

The oint allows a

small angularmoment of one rod

relative to another

It can be easily

connected and

disconnected



Biodata Biodata Biodata Biodata!!!!!!!!

• Used for different types of connections e.g. tie

rods, tension links in bridge structure.

• One of the rods has an eye at the rod end and

legs.

• A pin (knuckle pin) is inserted through the rod-

end eye and fork-end eyes and is secured by acollar and a split pin.



• In the knuckle joint illustrated, the rods are

integral with the eye and fork (forged

construction).

• However, the knuckle joint is often separate to

t e ro s, an t e ro s nee to e we e orscrewed into the eye and fork.



Isko Kahi Dekha hai???



7812 Erlestoke

Manor



Talk about its Design!!!!!

• Normally, empirical

relations are available tofind different dimensionsof the joint and they are

sa e rom esign point oview.

• The proportions are givenin the figure-1





Bomb Explodes…..So Does every

Assembly!!



Empirical Relations!!

(White Hair Relations☺☺☺☺ )

• d = diameter of rod

• d1 = d t =1.25d

• d2 = 2d t1 = 0.75d

• 3 = .5. t2 = .5• Mean diameter of the split pin = 0.25 d

• The analyses are discussed in following section

assuming the same materials for the rods and pinsand the yield stresses in tension, Compression andshear are given by σt, σc and τ.



Party HiParty HiParty HiParty Hi----CommandCommandCommandCommand ChintanChintanChintanChintan Baithak Baithak Baithak Baithak ☺☺☺☺(Failure Analysis)

3. Failure of knuckle pin in bending (if the pin is loose in the fork):Assuming atriangular pressure distribution on the

pin, the loading on the pin is shown infigure 2Equating the maximum bending stressto tensile or compressive yield stresswe

Have:





The design may be carried out using the empirical proportions and then the

analytical relations may be used as checks.

For example using the 2nd equation we have.

We may now put value of d1 from empirical relation and then

find

which should be more than one.



Any Problems??

NO??

Okieezz!!

Then I’ve a Problem for You!! ☺☺☺☺

• Two mild steel rods are connected by a knuckle joint

to transmit an axial force of 100 kN. Design the joint

completely assuming the working stresses for boththe pin and rod materials to be 100 MPa in tension,

65 MPa in shear and 150 MPa in crushing.



Calci,..Paper,..Pen!!

For failure of rod in tension, On substituting P=100 kN

σy = 100 MPa we have d= 35.6 mm.Choose the rod diameter d = 40 mm which is the next standard size.

Use the empirical relations to find the necessary dimensionsand then check the failure criteria.



Here they are…This is ‘em…!!!

d1= 40 mm t= 50 mm

2 = mm t1= mmd3 = 60 mm t2= 20 mm

split pin diameter = 0.25d1 = 10 mm



Party HiParty HiParty HiParty Hi----CommandCommandCommandCommand ChintanChintanChintanChintan Baithak Baithak Baithak Baithak ☺☺☺☺

(Failure Analysis)







What’s Your Rasheee???

• d1 = 55 mm t= 50 mm

• d2 = 90 mm d= 40 mm t1= 30 mm• d3 = 60 mm t2= 20 mm



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Knucle Joints