Hi, you may find useful the following links. Manuals on the design of cardan joints are scarce. I recommend the book of Wagner (Published by SAE) and a book by Duditza. This last book was originally written in roumenian, but there is a french translation by Eyrolles. Although little known by...
I recommend a book from F. Duditza "Cardan joints". Originally written in roumenian, a french translation has been published also by Eyrolles. It's classical and excellent source for people seriously involved in the design of cardan joints. If you are interested in equations and modeling...