The role of the humble ball bearing is often neglected when people talk about the engineering under the bonnet of our biggest machines, but it is absolutely vital to ensure vehicles and machinery run smoothly.
According to new research by scientists at the UK’s University of Exeter, ball bearings could have been absolutely vital for the ancient engineers that built the Stonehenge monument in southern England over 4,000 years ago.
If they are proven right, it may help solve one of the great outstanding mysteries of ancient engineering, namely how the neolithic builders of Stonehenge were able to shift the monument’s great “Standing stones” standing stones, estimated to weigh 4 tonnes each, from their quarries to Salisbury Plain, 150 miles away.
In many ways, the construction of Stonehenge was one of the earliest examples of multi-phase construction. Today we talk of multi-phase projects sometimes extending over a few years, but it took thousands of years for Stonehenge to reach completion.
In fact the site of what remains of the monument was built upon and added to from 8000 BC to 1600 BC.
The second phase of Stonehenge’s construction is gen-erally viewed as a timber circle that was originally built in 3100. This lasted roughly 500 years before the site entered its third phase in circa 2600; and the stone circle that we now recognise as Stonehenge began to take shape.
Many theories have been suggested and championed as to how the massive stones were transported but no-one has yet successfully explained how the slabs crossed the bleak wilderness from quarries in Pembrokeshire, Wales to their final resting place on theWiltshire Plain.
The hard surfaces and trenches needed if they, like ancient Egyptian engineers, had used rollers have thus far proven elusive to find or prove. In fact, every failed attempt to re-enact transporting the blocks on wooden rollers or moving them by water has only added to the mystery behind Stonehenge’s construction.
The new research by the scientists suggests that balls placed in grooved wooden tracks would have allowed the easy movement of stones even if they weighed many tonnes.
Experts hit on the new idea after examining mysterious stone balls found near Stonehenge-like monuments in Aberdeenshire, Scotland.
About the size of a baseball, they are precisely fashioned to be within a millimetre of the same size.
This suggests they were meant to be used together in some way rather than individually. The Scottish stone circles are similar in form to Stonehenge, but contain some much larger stones.
To test the theory, the researchers from the University of Exeter constructed a model in which wooden balls were inserted into grooves dug out of timber planks.
When heavy concrete slabs were placed on a platform above the balls, held in position by more grooved tracks, they could be moved with ease.
Professor Bruce Bradley, director of experimental archaeology at the University of Exeter, said: “The demonstration indicated that big stones could have been moved using this ball bearing system with roughly ten oxen and may have been able to transport stones up to ten miles per day.”
Although the ball bearing theory may help explain the transportation, scientists and engineers are still confounded by how the mighty stones were lifted into place.
One lintel that fell in 1797 had to wait almost two hundred years and the advent of the industrial revolution before a 60 ton crane (one of only two of its kind in the UK at the time) could lift the 18 ton stone back into its place in 1958.
