This thing is obsolete. Here is the next generation version: http://www.thingiverse.com/thing:7831 This thing is an experimental printable elastomeric coupling designed for a molded and cured-in-place rubber insert.The rubber part is cured-in place RTV silicone sealer.It has robust clamping, and should be well balanced if tightened evenly.Heritage:This is a variation of:http://www.thingiverse.com/thing:7678based on the suggestion there by JelleAtProtospace================================= AFTER I BUILD AND TEST THIS THING, I THINK IT FAIL.Basically the silicone takes a long time to cure and is too soft. Overloads tend to make it want to go off center.I do not recommend making this thing.Print the parts. Use a solid profile for strength. Clean up. Run a 3mm drill through the clamping holes.The clamps will have good clamping force, but limited travel. The part should press onto the shafts with some reasonable force. If they are loose on the shafts, please make the shaft hole sizes slightly smaller and re-print.The idea is to fill the cup with RTV silicone sealer, and drop the top piece in. Kind of jiggle it around to work the silicone in all the spaces. edit: Let it cure 24 hours in a warm place (on a heat vent or a sunny window sill).24 hours was no where near cured. I need to re-think that.Clean off the excess silicone by rubbing, then carefully cut the thin alignment triangles off the top piece.If more flexibility is needed you could carefully remove the thin cylinder of the bottom piece that was used to hold the silicone in place while it cured.Other materials could be used to get other stiffness. Maybe Sho Goo ( http://bit.ly/hc11mc )?If you build this, please feed back what you use and how it works for you -- thanks!