Ball Bearings: Motion Technology for a Spinning World
by Marjorie Steele, Editor at IQS
Leonardo da Vinci is credited with introducing the modern ball bearing circa 1497, adding friction reduction to his long list of useful, functional and not-so-functional inventions. Da vinci was not the first to come up with ideas for friction reduction or motion improvement, however; ball bearings have been found on “luxury yachts” of the Roman Empire dating back to 40 A.D., and the basic technology of linear roller bearings has been used in the building of many monuments of ancient civilizations, such as Egypt’s Giza pyramids and possibly Great Britain’s Stonehenge. Just as multi-ton blocks of stone were transported long distances by being rolled across bearings of logs and platforms, modern motors, axles and even building columns are given movement and stability by the modernized ball bearing (Fig. 1).
Fig. 1 Fig. 2
Motion produces friction, one of the primary causes of fatigue and equipment failure. Ball bearings dramatically reduce both these problems by reducing friction to a minimum, as well as providing stability of movement. Placed at exact intervals between two “races”, or solid rings, perfectly spherical ball bearings move freely within their races to provide easy, virtually frictionless radial or thrust movement. Radial movement occurs when a bearing’s outer race spins to reduce friction in belt movement, wheel movement or other circular movement applications; roller bearings (Fig. 2) utilize the same design with bearings that are cylindrical instead of spherical, providing rolling movement for load handling applications such as conveyor belt movement. Thrust movement occurs when a load bears down on bearings and/or their races directly, allowing the load to spin freely clockwise or counter-clockwise, like in a spin-top bar stool or lazy susan. Radially turning ball bearings and thrust bearings join linear rolling bearings in providing free motion in an exhaustive range of light-load conveyors, wheels, motors, clutches, axles, inline skates, household appliances and hardware. High turning speeds can be achieved with minimum friction in many precision applications with the help of radial and thrust ball bearings (Fig. 3), which can function almost indefinitely with little or no lubrication.
Fig. 3 Fig. 4
Because ball bearings are usually used in light load applications which apply smaller amounts of pressure, tools with spinning action are an ideal application for miniature ball bearings (Fig. 4). Dentist and medical instruments such as drills use stainless steel miniature ball bearings for their corrosion resistance and precision. Computer hard drives, wristwatches, bicycles, wind turbines and turbine engines also use ball bearings to produce spinning motion with the least amount of friction resistance. Although Leonardo da Vinci’s ball bearing and early clockmakers’ miniature bearings were fabricated from wood, most modern ball bearings are fabricated from steel, stainless steel and chrome steel. Advances in ceramic technology have introduced ceramic ball bearings as a solution to larger load and higher fatigue applications, since ceramic materials offer superior hardness, corrosion resistance and wear resistance.
One of modern technology’s most fascinating applications of ball bearings can be found at the San Fransisco International Airport. Located in a place which is historically known for earthquakes, the airport building has been recently redesigned for earthquake resistance with 267 supporting columns which rest on large ball bearings five feet in diameter each. The top section of column, which rests on the enormous steel bearing, is grooved to the size and shape of the bearing to lock it into place, while the bottom section of each column is scooped to allow the bearing free movement along a shallow bowl. Were an earthquake to occur, the bottom section of the column could move up to twenty inches off center without breaking or toppling the upper column; this is due to the ball bearing’s freedom of movement on the lower column. Just like the Great Pyramids of Giza built nearly 5,000 years ago, this feat was made possible by the basic technology of bearing movement.
It’s amazing to see technology advance through human civilizations. Just as man advanced from the discovery of fire to the invention of the hot air balloon to precision polymer sintering, the invention of the wheel in our dark prehistoric past founded motion technology as we know it. Like the wheel, ball bearing technology has become one of the pillars of modern engineering, and its advances keep us rolling into a future of what may one day be limitless motion.