ocumentdescription for your document, Study notes for Theory of Machines

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Revolute Prismatic Screw 1 Degree of Freedom Degree of Freedom = 1 Degree of Freedom Cylindrical Spherical Planar 2 Degrees of Freedom 3 Degrees of Freedom 4 Degres I Kinematics Chain When the kinematics pairs are coupled in such a way that the last links is joined to the first link to transmu 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 pairs, joined in such a way that each link forms a part of two pairs and the relative motion between the links or elements ts completely or 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 o} 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 pairs (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: sa 31-2 2 Mechanism When one of the links of a kinematics chain is fixed, the chain is known as mechanism, It may be used for transmitting or transforming motion e.g, engine indicators, typewriter etc, co A mechanism with four links is known as simple mechanism and the mechanism with more than tour links a compound mechanism, When a mechanism is required to transmit power or to do some par oe , ne particular type of work it then becomes a machine, In such cases, the various links or ¢lements have to be de a forces (both static and kinetic) safely, § have to be designed to withstand the A little consideration will show that a mechanism may be regarded ; : as a machine | nN art 1h recuees to the simplest form to transmit the required motion, | a oe
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