Types of constrained motion

Types of constrained motion :

• Completely constrained motion 

When the motion between two elements of a pair is indefinite direction irrespective of the direction of the force applied it is known as completely constrained motion.

The constrained motion may be linear or rotary.

Example of completely constrained motion :

• The sliding pair 
• The turning pair 

In sliding pair, the inner prism can only slide inside the hollow prism.

In case of the turning pair, the inner shaft can have only rotary motion due to the collar at the ends. 
In each case of force has to be applied in a particular direction force required motion.

• Incompletely constrained motion 

When the motion between two elements of a pair is possible in more than one direction and depend upon the direction of the force applied that motion is known as incompletely constrained motion. 

Example of incompletely constrained motion :

• The inner shaft may have sliding or rotary motion depending upon the direction of the force applied if the turning pair does not have a collar.

Each motion is independent of the other.

• Successfully constrained motion 

When the motion between two elements of a pair is possible in more than one direction but with the using of some external means motion is made to have only in one direction so that motion is known as successfully constrained motion.

Example of a successfully constrained motion :

• A shaft in a footstep bearing may have vertical motion apart from rotary motion but due to the load applied on the shaft, it is a constraint to move in that direction and thus is successfully constrained motion.
•  A Piston in a cylinder of an internal combustion engine is made to have only reciprocating motion and no rotary motion due to constraining of the piston pin. 
• The value of an IC engine is kept on the seat by the force of a spring.