The Nikkei Business Daily（日本空心弹簧）

NHK SPRING CO. DEVELOP HOLLOW SPRINGS
February 9 2008.


Japanese company, NHK Spring Co., has developed new suspension coil springs from hollow bars of steel, making them stronger than conventional products but 20% lighter. 


The firm aims to ultimately develop products 30% lighter and hopes to have samples ready for shipping in 2010 for both cars and motorcycles. 


Its new spring is made by boring out a steel bar to create a tube that is then wound into shape. The material itself is made from an alloy of iron mixed with nickel, vanadium and other rare metals, just like conventional suspension coils. By carefully adjusting the mixture, NHK Spring obtained a material that when shaped as a tube has a tensile strength of 2,000 megapascals, or roughly double that of conventional piping. The material is then further strengthened by subjecting the interior of the tube to a procedure known as shot peening. 


NHK Spring will also work on a way of mass-producing the new suspension coil. The coil now costs more than twice as much to make as conventional products, so the biggest challenge is reducing the manufacturing costs.