Link or element

Every part of the machine which is having some relative motion with respect to some other part will be known as link or element.

It is necessary for the link to be a resistant body so that it is capable of transmitting power and motion from one element to other element.





Types of links

1. Rigid links-

The link in which deformations are negligible. Examples are crank, connecting rod, piston, cylinder

2. Flexible link-

In flexible links deformations are not negligible but under permissible limits. Examples are belt, rope, chain drives

3. Fluid link-

When the power is transmitted with the help of fluid pressure than it acts as fluid link. Examples- in case of hydraulic brakes break oil is used which is our fluid link. Similarly fluid used in torque converter, hydraulic ram, hydraulic jack are fluid link





RELATIVE MOTION

Different types of relative motion





2. Successfully constrained motion - system in which desired motion is obtained with the help of some force or external body.

In given figure of piston cylinder arrangement, rotating motion of piston is stopped by connecting rod which is not part of system it is surrounding





3. Incompletely constrained motion- the system in which we get two or more than two motion which are undesirable.





In below figure a cubical block having a hole of circular cross section inserted with a circular rod is example of incompletely constrained motion. Here both rotating and to & fro Motion are there.





Relative motion for links are defined as the motion of one link with respect to other moving or fixed link. For a motion system will be having 2 links.In below figure a cubical block (considered as link 1) have a hole of square cross section and a long rod (considered as link 2) with same cross section is pass through it. In this case only one motion can takes place that's to and fro. This is the example of self constrained motion.