Roger, I'd just switched off my PC last night when I decided to check some of my books. My "Mark's Engineer's Handbook" shows both Zeuner and Reuleaux diagrams and how to construct them. I'll scan the pages for you (I'd like to say tonight, but let's say sometime this weekend to be on the safe side!) and send them direct to you. If anyone else wants copies, let me know and I'll send them to you. Cheers, JohnP MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.