Universal joint

Universal joint is also referred as Cardan joint, Hooke’s joint, U joint, universal coupling. It is a mechanical joint where rigid rod bends in desired direction to transmit shaft motion. It has pair of hinges which are so close together and perpendicular to each other. Hinges are connected together by cross shaft.

History of universal joints

In ancient days, gimbals were used as unique representation of universal joints. Gerolamo Cardano was the first to propose the idea of transmitting power through universal joints in the year 1545. One such working model named Cardan shaft or Cardan joint. Cardan joint includes problem in speed variation. Gaspar Schott described mechanism of operation as paradoxum in the year 1664.  It was misunderstood as constant velocity joint. Later Robert Hooke investigated the change in rotation speed during 1667 and 1675. Equation of time of Robert Hooke calculated mathematical universal joint description. He was the first to device universal joint in 1676.  This term universal joint became familiar in 18^th century and more common in 19^th century.

Metal coated universal joint was first patented by Edmund Morewood’s in 1844. Lardner published handbook in 1877. He described the universal joint and double universal joint in detail. It was used in cotton mill line shaft system. Mathematics and mechanics behind universal joint was described by Jules Weisbach in 1883. Universal joint was widely used in 19^th century. Control shafts were linked using universal joints in Northumberland telescope at Cambridge University in the year 1843. Ephriam Shay obtained his patent in the year 1881. He used double universal joints in locomotive drive shaft system. Small universal joint was used in bit brace by Charles Amidon. He obtained patent for the same in 1884.

Questions:

• What are equations of motion?
• What is double cardan shaft?
• What is double cardan joint or constant velocity joint?
• What is Thompson coupling?