Six-bar linkage

This article is about the mechanism with six rigid links and seven joints. For the tensegrity structure with six struts and 24 cables, see Jessen's icosahedron.
Six-bar linkage from Kinematics of Machinery, 1876
Six-bar linkage from Kinematics of Machinery, 1876

In mechanics, a six-bar linkage is a mechanism with one degree of freedom that is constructed from six links and seven joints.[1] An example is the Klann linkage used to drive the legs of a walking machine.

In general, each joint of a linkage connects two links, and a binary link supports two joints. If we consider a hexagon constructed from six binary links with six of the seven joints forming its vertices, then the seventh joint can be added to connect two sides of the hexagon to form a six-bar linkage with two ternary links connected by one joint. This type of six-bar linkage is said to have the Watt topology.[2]

A six-bar linkage can also be constructed by first assembling five binary links into a pentagon, which uses five of the seven joints, and then completing the linkage by adding a binary link that connects two sides of the pentagon. This again creates two ternary links that are now separated by one or more binary links. This type of six-bar linkage is said to have the Stephenson topology.

The Klann linkage has the Stephenson topology.

  1. ^ J. M. McCarthy and G. S. Soh, Geometric Design of Linkages, 2nd Edition, Springer 2010
  2. ^ An animation of a six-bar linkage with the Watt topology.