Surface en fil de fer, engendrée par une hélice et tracée sur un cylindre de rayon r

Wire surface based on a helix and created by Joseph Caron, professor of descriptive geometry at the École normale supérieure (ENS), on 16 November 1914. It is traced on a cylinder of radius r, rolled up in a coaxial cylinder of radius R > r. The surface contains three families of helices: those belonging to the cylinder of radius r are red, those belonging to the cylinder of radius R - r are blue, and those belonging to the cylinder of radius R are yellow. It forms part of a collection of mathematical objects at the Institut Henri Poincaré (IHP).