There have been some nice definitions of this linkage already, but I made one with a locus so you can see the range of motion traced out:
http://groups.google.co.uk/group/grasshopper3d/web/4barlocus.jpg?hl=en http://www.hotlinkfiles.com/files/2493951_sn1bk/4_bar_locus.ghx This was done mainly as an exercise in using paths and data trees, but I thought I'd share in case anyone else wants to have a play with it. (I first started exploring linkages years ago through this program called Cinderella: http://vimeo.com/3490609 It's great fun, and very quick to use, but limited to 2D and it's cool now to have GH for doing this kind of thing in 3D.)
