Hi All, As a school boy I can remember going to the local public library and diligently reading all the books on any kind of engine. Several books described a way of analysing steam engine valve events by drawing a circle and dividing it up and dropping perpendiculars etc. I would love to re-visit this technique, but cannot recall what these diagrams were called. So far searches on the Internet have proved fruitless, because I cannot remember (old age) the all-important name by which these diagrams were known. Can anyone help me out please? Cheers, Roger Mason, in St. Agnes. 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.