Another project has just been completed called Oldham's coupling named after the inventor John Oldham, (1779-1840) an Irish engineer. It is simple and compact, and unlike a universal joint it is constant velocity. Although it was invented about 200 years ago it is still used in many of today's machines in various forms.
My project was constructed by looking at the picture the Z5 thing shown above. Which was probably a classroom demonstrator.
Below is a short video of it in operation. In the video the shafts are offset slightly over 1/2". As you can see it works very free and easy. It is just so much fun to turn cranks.