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| Revolute Prismatic Screw L Degree of Freedom | Degree of Freedom | Degree of Mreedorn Cylindrical Spherical Planar 2 Degrees of Freedom 3 Degrees of Freedom 3 Degree ol bt Lent Kinematics Chain When the kinematics pairs are coupled in such a way that the last links is joined to the first link to transi definite motion (i.e. completely or successfully constrained motion) it is called a Kinematics chain. In other words, a kinematics chain may be defined as a combination of kinematics Pulrs, joined In Such a Way Ihat each link forms a part of two pairs and the relative motion between the links or elements ts completely o successfully constrained. For example, the crankshaft of an engine forms a kinematics pair with the bearing which are fixed in a pair, the connecting rod with the crank forms a second kinematics pair, the piston with the connecting rod forms a third pair and the piston with the cylinder forms a fourth pair The total combination ol these links is a kinematics chain. If each link is assumed to form two pairs with two adjacent links, then the relation between the number of pans (p) forming a kinematic chain and the number of links (1) May be expressed in the form of an equation: L=2p-4 Since in a kinematic chain each link forms a part of two pairs, therefore there will be as many links as the number of pairs | Another relation between the number of links (1) and the number of joints (j) which constitute a kinematic chain is given by the expression: y= 3L-2 2 Mechanism When one of the links of a kinematics chain is fixed, the chain is known as mechani: transmitting oF transforming motion ¢.g, engine indicators, typewriter etc. A mechanism with four links is Known as simple mechanism and the mechanism with compound mechanism, When a mechanism is required to transmit it then becomes a machine, In such cases, the various links or e| forces (both static and kinetic) safely, A little consideration will show that a mechanism may be regarded to the simplest form to transmit the required motion, im, Wemay be used for : More than tour links as power or to do some particulay ype ol work ements have to be designed to withstand the as 4 machine in which each part i reduced 
