Layouts of spatial motion structures 145
7.3 Assemblies of Myard linkages
7.3.1 Building blocks
The Myard linkage (Myard, 1931; Baker, 1979) consists of five bars, one
of which has zero length. An umbrella- shaped motion structure, Figure
7.8, was reported consisting of a series of circumferentially connected
Myard linkages (Briand and You, 2007). When the assembly consists of n
identical Myard linkages, there are n joints at the centre point. Because the
frame forms a flat polygon when fully expanded with each Myard linkage
forming a triangle, the twist of each Myard linkage at centre must be
α 12 = π/n. The assemblies with n = 3, 4 and 6 can be represented schematically by a triangle, square and hexagon, respectively, which can be used as
(a)
(b)
Figure 7.7 (a) Models of the Case IV assembly. The twists of the Bennett linkages
are governed by (a) Eq. (7.5a) and (b) Eq. (7.5b), respectively.
7.3 Assemblies of Myard linkages
7.3.1 Building blocks
The Myard linkage (Myard, 1931; Baker, 1979) consists of five bars, one
of which has zero length. An umbrella- shaped motion structure, Figure
7.8, was reported consisting of a series of circumferentially connected
Myard linkages (Briand and You, 2007). When the assembly consists of n
identical Myard linkages, there are n joints at the centre point. Because the
frame forms a flat polygon when fully expanded with each Myard linkage
forming a triangle, the twist of each Myard linkage at centre must be
α 12 = π/n. The assemblies with n = 3, 4 and 6 can be represented schematically by a triangle, square and hexagon, respectively, which can be used as
(a)
(b)
Figure 7.7 (a) Models of the Case IV assembly. The twists of the Bennett linkages
are governed by (a) Eq. (7.5a) and (b) Eq. (7.5b), respectively.