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

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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

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