The cardan suspension

UNESCO Courier, Oct, 1988

The "cardan suspension", or gimbals, takes its name from Jerome Cardan (Girolamo Cardano, 1501 -1576). But Cardan neither invented the device nor claimed to have done so. He merely described it in his very popular book De subtilitate rerum (1550; "The Subtlety of Things"). It appeared in Europe as early as the ninth century AD; but it was invented in China by the second century BC at the latest.

This invention is the basis of the modern gyroscope, making possible the navigation and "automatic pilots' taken for granted in modern aircraft. Anyone who has been fortunate enough to enter a nineteenth-century Gypsy caravan will have noticed affixed to the walls the brass gimbals that hold lamps which remain upright no matter how violently the cart may jolt on the road. These interlocking brass rings can be moved around as much as you like, but the lamp suspended in the centre never turns over. This is the basic idea of the cardan suspension". A series of rings inside one another are each Joined at two opposing points, enabling them to twist and turn freely.

Consequently, if a heavy weight, such as a lamp, is positioned upright in the centre, itwill remain upright. Whatever motions might occur to the rings around it will be taken up by the rings themselves, leaving the lamp unmoved. By the eighteenth century, Chinese mariners were using a gimbal-mounted compass. A ship's magnetic compass mounted in this way was free of disturbance by waves.

The earliest textual reference to gimbals which has been found is in a poem called Ode on Beautiful Women, composed about 140 BC. More than three centuries later, about 189 AD, the clever mechanic Ding Huan was given credit for inventing gimbals a second time.

Gimbals reached Europe after 1,100 years. And 800 years after that, the English physicist Robert Hooke and others adopted its principle in a new form, applying power from without rather than stabilizing a central element within, to formulate that Western invention, the universal joint. And it was this invention which resulted in the transmission of automotive power in contemporary motor cars.