Mechanisms

Mechanism

An assembly of rigid bodies or links designed to obtain a desired motion from an available motion while transmitting appropriate forces and moments. Motion of the links have definite relative motion with other links.

Simple mechanisms

• Lever
• Pulley
• Gear trains
• Belt and chain drive
• Four bar linkage

Other complex mechanisms

• Lock stitch mechanism (used in sewing machine)
• Geneva mechanism
  Constant rotational motion to intermittent rotational motion. mostly used in watches.
• Scotch yoke mechanism
  Constant rotational motion to linear motion (vice versa.). Mainly used as valve actuators in high pressure gas pipelines.
• Slider crank mechanism
  Used in internal combustion engines

2D link mechanisms

Method of instantaneous centre of rotation

• Find the instantaneous centre of the rotation from known velocities at known points
• Use the instantaneous centre to find velocities at other points

Kinematic chain

An arbitrary collection of links (forming a closed link) that is capable of relative motion and that can be made into a rigid structure by an additional single link.