Kinematic Link: Definition, Types, Example [PDF]


A kinematic link or element is a resistant body that constitutes to part of the machine, connecting other parts which have motion relative to it.

Piston, piston rod and crosshead of a steam engine constitutes one unit and hence called one link as shown in the below figure. In this figure, the various link is designated as 1,2,3,4, etc.

kinematic link diagram

Link 1 is a fixed link that includes frame and all other stationery parts like cylinder, crankshaft bearing, camshaft bearing, etc.

Link 2 is the crankshaft, flywheel, etc. all having rotatory motion with respect to a fixed axis.

Link 3 is the connecting rod and

Link 4 is the piston which is having reciprocating motion. Hence this is called a 4 bar mechanism.

Link need not be a rigid body but must be a resistant body. Hence link must have the following two characteristics:

  1. It must be a resistant body.
  2. It must have relative motion.

There are basically 4 types of the link which are as follows:

  • Rigid Link
  • Flexible Link
  • Fluid Link
  • Floating Link

A rigid link is one that does not undergo any deformation while transmitting motion. Links, in general, are elastic in nature. They are considered rigid if they do not undergo appreciable deformation while transmitting motion.  For Example, crank and connecting rod.

A flexible link is one which while transmitting motion is partly deformed in a manner not to affect the transmission of motion. For Example, Spring, Chain, Rope, Belt, etc.

A fluid link is one that is deformed by having fluid in a closed vessel and the motion is transmitted through the fluid with pressure. For Example, hydraulic press and hydraulic jack.

A floating link is one that is not connected with the frame.

  1. Binary Link
  2. Ternary Link
  3. Quaternary Link.

It has two vertices.

It has three vertices.

It has four vertices.

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