Good people, see attached PDF, could anyone out there comment on how I could possibly get from the enclosed code to the image produced on page 2. I have been trying to adapt the radial engine demo to a rotary engine, so accept that some variable and functions may have been referenced in global memory. I even stripped a lot of code out. Accordingly I closed Mathematica down and even rebooted the iMAC, which in my mind should have cleared all memory, but it seems it hasn't . Is it possible the .NB file has echoes of the old source left in it?