Eye a of link 1 fits with a large clearance over pin d of link 3. Eye a slides between cheeks b of link 3, its motion being limited by pin d. Link 3 has trunnions e fitting into holes in prongs f of link 2. With respect to each other, links 1 and 2 accomplish two turning motions about parallel axes x-x and x' -x' , and two translational motions along perpendicular axes x-x and y-y.
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