Can anyone tell me if a four bar linkage can be made in such a way that something attached to one of the bars can be made to orbit around a known, fixed point? I know... it's hard to visualize. I'm trying to think up a way to have a "virtual" pivot point in a mechanism, without having any connections at that point.
In the attached (very) quick sketch, C is the centre point what I want X to rotate around. X needs to be affixed to the base, B, by some sort of linkage, slide, or whatever. Y shows another position of X on the arc of travel. Nothing can be attached to C. Think of X as a cube or rectangular block with 3 dimensions.
Simple and rigid, with the ability to lock and unlock to reposition easily.