The cord used in San Wu is made of specially developed High Carbon Steel. When manufacturing the belts, the high tensile strength cord is held longitudinally in a single layer under pre-tension to ensure proper alignment. The standard constructions steel cord used are 7×7 and 7×19. These cords are coated suitably with zinc to protect the same from corrosion as well as to ensure superior bonding between cord and rubber. Filaments constituting the cord have lower elongation and high flexibility. Ratio of diameter of core to outer strand are so designed that penetration of rubber into the cord interstices is maximized. The penetration has multifold effect e.g notching effect of the wire against one another is prevented, corrosion resistance is increased, strength is increased, elongation is reduced. Alternate application of S & Z lay cord eliminates the accumulation of residual torsion.
