Fundamental concepts 27
2.3.5 The Bricard linkages
Among six- bar overconstrained mechanisms with revolute joints, the most
remarkable are the Bricard linkages. Bricard reported three different types
of mobile 6R linkages when he was investigating octahedra (Bricard, 1897)
and later he added three more types, namely the line- symmetric, the planesymmetric and the trihedral linkages (Bricard, 1927). All of the six types
and their associated geometrical conditions are summarised as follows
(Baker, 1980; Phillips, 1990).
(d)
Figure 2.16 continued.