Conceptual Dynamics - Independent Learning

General Planar Motion




Many mechanisms that you will see in real life have constrained motion. Motion is constrained when the mechanism is forced to move in a particular way.


Examples of machines that exhibit constrained motion:


  • Train on a train track.
  • An engine piston.
  • A car must follow the ups and downs of a road.


Linear bearings / collars


Linear bearings and collars are sleeves that fit around or on shafts. They constrain motion to be in the direction of the shaft.



A good example of a machine with linear bearings is an exercise machine.




A slot constrains the motion of a pin, for example, to move in the direction of the slot.


An example of a slot constraint is a Geneva wheel. A Geneva wheel changes continuous rotary motion to periodic motion.





Joints can restrict the motion of mechanisms to which they are attached.



Surface contacts


Surface contacts constrain the motion of some point on the rigid body to the profile of the surface, such as a car on a road.