Four Bar Chain

A Four Bar Chain is a linkage with four pivots, two of which are fixed - the bed or surface they are fixed to may be regarded as the fourth bar or link.

Varying the lengths of the links can cause the output to speed up or slow down and describe a different arc to the input. The lengths of links can be arranged such that a continuous rotary motion input can result in an output with oscillatory motion.

Examples of the use of 4 Bar Chains can be found in vehicle suspension and steering systems.