Cardan

Cardan is a surname associated with several notable concepts that ultimately trace to the Italian polymath Gerolamo Cardano (often anglicized Cardano; 1501–1576). Cardano’s wide range of work in mathematics, medicine, and astrology left a lasting imprint on many fields, and a number of eponymous terms in science and engineering honor his name. In English-language sources, Cardano is the more common form, but Cardan appears in several technical names that preserve the association with him.

Cardan joint. Also known as a universal joint, the Cardan joint transmits torque between two shafts that intersect at an angle. It uses a pair of hinges connected by a shaft, allowing angular misalignment while transmitting rotation. The joint introduces nonuniform output velocity, an effect that can be mitigated by using a double Cardan arrangement in modern driveshafts or by other compensating mechanisms.

Cardan grille. The Cardan grille is a steganographic technique named after Cardano. It involves a perforated card or grille placed over a sheet of text; by rotating the card, different letters are revealed to form a hidden message. The method originated in the Renaissance and has been studied as a cryptographic and puzzle device, illustrating early practical applications of masking and transposition.

Overall, Cardan refers to several distinct concepts in history and engineering, all connected to Cardano’s legacy through naming.