Smooth operating

If the city of Gothenburg hadn’t been built on a thick layer of clay soil, the Swedish engineer Sven Wingquist wouldn’t have invented the self-aligning ball bearing. Then again, maybe he would have – it’s difficult to tell how much inspiration an inventor draws from within, and how much comes from their external circumstances.

In the early 20th century, Wingquist was a young maintenance engineer at the Gamlestadens Fabriker textile mill. He faced a problem: the mill’s large looms, which were operated by steam engines via long drive shafts that went right up into the roof. The drive shaft bearings kept breaking down, and replacements had to be ordered from abroad. Wingquist determined that the breakdowns were caused by barely perceptible settling of the ground, which slightly shifted the drive shaft beyond the tolerance of the bearings. The result was that the machinery would jam, increasing the risk of fire.

The principle of roller bearings had been known since ancient times, when the Egyptians transported massive stones over cylindrical logs to build the pyramids. The Romans refined the technology by using wooden spheres for tasks like rotating statue plinths –which apparently was a fairly common activity in the Roman Empire. Leonardo da Vinci – yes, him again – was the first person to set out the theoretical principle of ball bearings in his famous notebooks. But ball bearings did not come into widespread use until the 19th century, first in horse-drawn carriages and bicycles, followed by industrial machinery with moving parts.

Wingquist had trained as a textile engineer and spent some time working in the United States. He kept abreast of new international developments. Around the turn of the 20th century, a debate raged about what sort of friction bearing was superior: slide bearings, in which all the parts of a moving machine slid against each other with a layer of oil or grease to lubricate them; or ball bearings, in which metal spheres rolled around in a track, called a raceway.

In 1902 Richard Stribeck, a German professor of metallurgy, presented evidence that a ball bearing was more efficient. That led Wingquist to consider possible improvements that could protect ball bearings from wear and tear when they were subjected to pressure on their raceway, such as when the ground settled. Wingquist set up an experimental workshop near the textile mill. In 1906 he took out a patent on a spherical ball bearing. The raceway in which the ball assembly moved was rounded, which made it less sensitive to lateral pressure. However, this ball bearing performed less well under axial loads – that is, movement in the same direction as the rolling of the ball assembly.

Ball bearings help reduce friction and improve reliability –thereby saving energy. SKF has manufactured ball bearings of all sizes since 1907.

Following pages: Bearings more than 2 metres across are installed in a cable drum for NOV, a Norwegian offshore energy company.

The mill’s executives, who had been sceptical of Wingquist’s ambitions at first, realised that their young engineer was on to something. They contributed start-up capital for a subsidiary to develop his ideas. The new company was called Svenska Kullagerfabriken (‘Swedish Ball-Bearing Factory’), or SKF for short.

In the spring of 1907, Wingquist submitted a patent application for a multi-row, self-adjusting radial ball bearing. Its distinguishing feature was its two rows of balls, with a raceway in the outer ring that enabled the bearing to withstand axial pressure. The invention was widely known as a ‘self-aligning ball bearing’ and it made SKF into one of Sweden’s most successful companies. Wingquist, always thinking ahead, had also patented his invention in other major industrial countries. With subsidiaries in Germany, the UK and the United States, SKF became a global leader.

Today, we are surrounded by ball bearings. They are inside our washing machines, vacuum cleaners, fans, computers and many other devices in our homes. An average household will contain between 100 and 200 ball bearings. Some of them are tiny. The smallest ball bearing is around half a millimetre across. But there are also huge slewing bearings, such as the one with a diameter of 13 metres that is part of a Canadian oil-drilling rig. Ball bearings are also used to protect buildings against earthquakes. For example, the San Francisco airport stands on a large number of piles, each of which rests on a ball bearing measuring 1.5 metres in diameter.

Assembling roller bearings in 1959. Roller bearings are a variation on ball bearings. Both types of bearings need to support heavy loads, so they are manufactured from vacuumtreated steel free from cracks and impurities.