The Bricard linkages 125
collinear to one another. Although bifurcation exists, it does not cause any
problem in motion because the links would have to penetrate each other in
order to reach the bifurcated position, which is physically impossible.
6.2 Alternative forms of threefold- symmetric Bricard
linkage
Although the original threefold- symmetric Bricard linkage can be folded
up to a compact bundle, its realisation requires the use of the hinge design
introduced in Section 5.7. It has been found however that alternative forms
of this linkage also exist similar to the Bennett linkage, which allows much
simpler connections among the links.
The method to indentify the alternative form of threefold- symmetric
Bricard linkage is the same as that for the Bennett linkage. The axes of
(a)
(b)
(c)
Figure 6.12 Model of a motion assembly of threefold-symmetric Bricard
linkages.