Link 1 has pin a fitting into a hole in end b of link 3. Ball-shaped head c, at the other end of link 3, fits into spherical half-collars d of link 4. Round trunnions e of link 4 fit into the holes in prongs f of link 2. With respect to each other, links 1 and 2 accomplish four turning motions about three perpendicular axes x-x, y-y and z-z, and about axis x' -x' , and one translational motion along axis x-x.
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