Kardán

Kardán, in Hungarian usage, most commonly refers to the Cardan joint, also known as a universal joint, a mechanical linkage used to transmit torque between two shafts that are inclined relative to each other. It consists of two yokes connected by a cross-shaped intermediary (the spider). As the input shaft rotates, the output shaft follows, but the angular velocity is not constant unless the shafts are aligned or two joints are used with proper phasing.

In terms of kinematics, a single Cardan joint at an angle beta relates the input angle and output angle by tan(phi) = cos(beta) tan(theta). The instantaneous speed ratio between input and output varies cyclically with the rotation angle, causing fluctuations in output speed. In automotive drivetrains, two Cardan joints arranged with opposite phase can cancel these fluctuations, producing a smoother transmission. Modern vehicles often employ constant-velocity joints (CV joints) to achieve near-uniform output speed without such cancelation schemes.

The term kardán derives from Cardano, Girolamo Cardano, the 16th‑century Italian mathematician after whom the device is named. The name is also associated with Cardan grille (Cardano grille), a steganographic method introduced by Cardano for hiding messages using a perforated template over text.

Other uses of the term in Hungarian technical vocabulary include generic references to universal joints or related bearings, such as kardáncsapágy, within mechanical drive systems. In summary, kardán most often denotes the Cardan/universal joint and its historical and practical adaptations in engineering.