The Schaeffler Group has developed an innovative, energy-efficient four-row, angular-contact ball bearing as a replacement for conventional tapered-roller bearings. Initially the intention is to use the design in wheel bearings to reduce fuel consumption and emissions on trucks, SUVs and light vans, but the potential exists to develop the technology for other heavy engineering applications.
By replacing the line contact of conventional tapered-roller wheel bearings with a new concept based on point contact ball bearings, the Schaeffler Group has developed the innovative 'twin tandem' bearing that reduces friction by around 50 per cent over conventional tapered-roller wheel bearings. The result is claimed to be a reduction in fuel consumption of around 1.5 per cent on trucks, light vans and SUVs.
At the Hanover Fair exhibition in April 2007, the new twin tandem wheel bearing was unveiled to the public for the first time. Visitors to Schaeffler's stand were invited to see a demonstration of the twin tandem in operation and its reduced friction characteristics. The demonstration comprised a complete wheel assembly with a conventional tapered roller wheel bearing on one end of the axle and the new twin tandem unit on the other. When the power was cut off, the conventional tapered roller wheel bearing continued to rotate for around six to seven revolutions. However, visitors were amazed to see the twin tandem unit continue to rotate freely for between 48 to 50 revolutions – clearly demonstrating its reduced friction properties.
Rib friction eliminated
By replacing two rows of tapered-roller bearings with two rows of ball bearings, a double-row tapered-roller bearing becomes a four-row ball bearing. This eliminates rib friction and is claimed to reduce overall friction by 50 per cent.
The twin tandem bearing also has a lower operating temperature compared to conventional tapered-roller units, therefore improving the service life of the lubricants. Cornering stiffness is also increased.
Initially developed for trucks, light vans and SUVs, where the 1.5 per cent reduction in fuel consumption and emissions will have the greatest benefit, the twin tandem design will undergo further work to make it suitable for passenger cars too. Schaeffler has carefully considered interchangeability of the new twin tandem with conventional tapered-roller units. The twin tandem bearing is designed to cater for the use of sensors (such as ABS sensors) and installation in the wheel carrier is identical for conventional tapered-roller wheel bearings.
Furthermore, similar energy-efficient design concepts are currently under development with customers in other manufacturing sectors, including heavy industries such as steelmaking, machine tools, paper and wind energy.