These are actually Hooke's type joints according to Mark's Engineering Handbook (9th Edition). It states "A constant velocity ratio of 1 between two main shafts may be obtained at any angle using two Hooke's joints and an intermediate shaft which must make equal angles with the main shafts. The
driving pins on the yokes attached to the intermediate shaft must be set parallel to each other."
I had to look it up. Been retired for 17 years from this sort of stuff.
Now I gotta check what I wrote earlier.......
