An optical illusion model based on an article in the Runnymede Meccano Guild Journal. The original was by Bert Halliday and then adapted by Andreas Konkoly. The top blue disc and fan should appear to “float” unsupported when the assembly is spinning sufficiently quickly.
I have updated this model slightly in time for a Runnymede meeting by replacing the wheel disc with a narrow matt black strip which allows the illusion to be seen very easily. Geoff Wright informed me that Bert Halliday took his inspiration for the original model from a display in a cycle-shop window — made from bicycle wheel rims and other parts.