Direct contact transmission:
In direct contact transmission of force and motion, such as in case of gear teeth, cam-slider etc., the consideration of friction plays an important role in designing the components. Since there is a sliding contact between the driver and the driven, it gives rise to frictional force which acts tangentially at the contact surfaces. In sliding contacts there is a combination of frictional force and sliding force, giving rise to the wear and tear of the components in contact.
It is important, therefore, to calculate the same. In the figure, posted above, the vector 'AM2' is the absolute velocity of the point 'A' (on Link-2). The vector 'AM2' will have two components namely 'AS' which is normal to the point of contact and 'AT2'; tangent to the contact surface. Assuming that the deformation, of the links in contact, is negligible and also that the contact between the the two links is continuous, the absolute velocity of point, 'A' (which a point on the link-3) is same as that at point 'A' (also a point on Link-2), therefore the components of the velocity must also be the same. To fulfil this condition, the absolute velocity of point 'A' on Link -3 is AM3 and tangential component becomes AT3
The velocity of sliding is the vector difference of the tangential components of the velocities of the point of contact. As the tangential components lie on the same line +ve and -ve are attributed to the directions from 'A'. The algebraic difference and the vector difference become equal.
It may be concluded, therefore, that the velocity of sliding is also equal to the the vector difference of the absolute velocities of the contact points i.e. the velocity of one contact point with respect to the other.
In direct contact transmission of force and motion, such as in case of gear teeth, cam-slider etc., the consideration of friction plays an important role in designing the components. Since there is a sliding contact between the driver and the driven, it gives rise to frictional force which acts tangentially at the contact surfaces. In sliding contacts there is a combination of frictional force and sliding force, giving rise to the wear and tear of the components in contact.
It is important, therefore, to calculate the same. In the figure, posted above, the vector 'AM2' is the absolute velocity of the point 'A' (on Link-2). The vector 'AM2' will have two components namely 'AS' which is normal to the point of contact and 'AT2'; tangent to the contact surface. Assuming that the deformation, of the links in contact, is negligible and also that the contact between the the two links is continuous, the absolute velocity of point, 'A' (which a point on the link-3) is same as that at point 'A' (also a point on Link-2), therefore the components of the velocity must also be the same. To fulfil this condition, the absolute velocity of point 'A' on Link -3 is AM3 and tangential component becomes AT3
The velocity of sliding is the vector difference of the tangential components of the velocities of the point of contact. As the tangential components lie on the same line +ve and -ve are attributed to the directions from 'A'. The algebraic difference and the vector difference become equal.
It may be concluded, therefore, that the velocity of sliding is also equal to the the vector difference of the absolute velocities of the contact points i.e. the velocity of one contact point with respect to the other.
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