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MECHANISMS
Prof. kiran gore
MECHANISMS
Mechanisms are used to obtain required motion in machines.
It is capable of transforming one type of input motion in to another.
How Mechanisms are made?
Mechanism consist of following elementLink or ElementKinematic PairKinematic Chain
What is a Link or Element?A resistant body, which is a part of machine and
has a motion relative to other connected part is known as an Element or Link.
CylinderPiston
Crank
Connecting Rod
What is resistant body ?
The body, which is capable of
transmitting the forces with negligible
deformation is called as resistant body.
CylinderPiston
Crank
Connecting Rod
Examples of Link or Element:Link1- PistonLInk2- CylinderLink 3- CrankLink 4 Connecting Rod
Kinematic Pair
2
What is a kinematics Pair?
When two element or link which are connected together
in such way that the motion between them is constrained
(in a definite direction) is known as kinematic Pair.
1.Kinematic Pair –ICrank & Frame
2.Kinematic Pair –IICrank & Connecting Rod
3.Kinematic Pair- IIIConnecting Rod & Piston
4.Kinematic Pair – IVPiston & Cylinder
1
23
4
Kinematic chainwhen the kinematic pair are connected in
such manner that the last link is joined to the first link to transmit completely or successfully constrained motion, then it is called as kinematic chain
Ex. Kinematic chain
MechanismsIf one of the links or element of a kinematic chain is fixed,
the arrangement can be used for transmitting or
transforming the motion, and it is called as Mechanism.
In short Mechanism is a kinematic chain with one link
fixed.
Example for Mechanism
Types of kinematic chain or Mechanism
1. Four bar chain or quadric cycle
chain.
2. Single slider crank chain
3. Double slider crank chain
Four Bar Chain
Four Bar Chain Mechanism
It is simplest kinematics chain, consists of 4
links & forming 4 turning pair; A0, A, B, B0. Each
link have different length.
If 1 link in 4 bar chain is fixed, then it is called as
bar chain Mechanism & other 3 links moves
relative to each other.
Four Bar Chain Mechanism
It is simplest kinematics chain, consists of 4 links &
forming 4 turning pair; A0, A, B, B0. Each link have
different length.
If 1st link in 4 bar chain is fixed, then it is called as 4 bar
chain Mechanism & other 3 links moves relative to each
other.
Slider Crank Chain A single crank chain is a modification of the basic four-
bar chain. It consists of one sliding pair and three
turning pairs.
It is found in reciprocating steam engine mechanism.
This type of mechanism converts rotary motion into
reciprocating motion and vice versa.
Links: Frame and cylinder, crank, connecting rod,
crosshead or piston.
First Inversion of a single slider crank chain
Reciprocating engine and Air compressor Links – 1- fixed
2- crank
3- connecting rod
4- slider
Slider Crank mechanism
Comparison between Mechanism & Machine
THANK YOU