Reprints Online

How about a little bet between us? Let's see if you know, or otherwise can guess, what object played an essential role in the building of all four items in this short list:

- your computer's Hard drive
- your grandfather's wrist watch
- Roman Emperor Caligula's Floating Palace
- San Francisco's International Airport

A little difficult, isn't it? Most likely, it's the third item that threw you off, isn't it? Don't feel discouraged, though: we haven't been able to reply, either, when we heard the same question, accompanied by a little smirk, during a conversation with our friends at TreErre. It must be said, though, that they were cheating: because the answer is the very object that Treerre deals in, that is, ball bearings.

Ball bearings really are one of those items for which it's tough to decide on a specific inventor, because, more or less like is the case for the wheel, it wasn't actually created at a specific point in time, but it was developed by successive improvements. Perhaps for this very reason, we find traces of bearings in the carriages of Vandals and Goths, who lived as nomads in the North of Europe mor than two thousand years ago, and mounted systems of roller bearings on their carriages' wheels. Romans themselves, as we saw, knew the principle behind bearings, and implemented it, for example, on Caligula's Floating Palac, one of the famous Nemi ships. And if the Middle Ages, as in many other cases, saw this technologu, and its knowledge, vanish from application, it is in the Renaissance that we find famous Leonardo da Vinci (and how could it be any different, actually) once again deducing the funding principles of bearings and applying them to some of his projects.

The technology which is needed to mass produce a truly efficient ball bearing, though, isn't trivial at all. La tecnologia necessaria a produrre in serie un cuscinetto a sfera davvero efficace, tuttavia, non è banale. The smoothing of the metal spheres, and the required precision in assembly, proved a practically insurmountable obstacle to mass production for several centuries after the times of our Leonardo, actually until August 3rd 1869, when Jules Suriray, a bicycle mechanic from Paris, was granted a patent for a tue ball bearing system. It can be nice to note an immediate triumph: Suriray mounted the newly patented bearings on the bicycle which, three months later, Moore mounted to win the Paris-Rouen, the first bicycle race in history. And it was finally in Sweden, forty years later, that Sven Wingquist, aged thirty, founder of SKF, the largest manufacturer of Ball Bearings in the world, patented the self-aligning ball bearing which we still use today.

But that's enough history. Before we say bye, perhaps you'd like to know something more about the real practical applications of this object which is so ancient and so modern at the same time. Are you still curious about how ball bearings could ever be linked to the construction of San Francisco's International Airport?

Well, the answer is quite particular indeed. As you probably know, the entire area where the city of San Francisco lies is at high seismic risk. For this reason, the entire airport was built to rest on 267 columns, whcih sustain its weight: and each of this column, in turn, rests, inside a concrete cell, on a large, five-foot diameter ball bearing. Should there be an earthquake, this system allows the airport to ignore ground movements of up to twenty inches, as the bearings insulate the columns from the tremors. Once danger is past, gravity itself realigns each column on its base.
One thing's for sure, ball bearings have come a long way since that Paris-Rouen race in 1869...