All the magnets are the same size 5mm rod (which will be the core of the coil), this bad sketch i did for Dean helps visualize...




(it's probably worth pointing out, that the above sketch was a simplified version of how it'll look....and only used for testing. The coils will not eventually be visible ...as I intend mounting them into some CNC milled perspex. The only bits you'll see arethe tips of the magnets protruding above the perspex holder)