Development of Low Cost Aluminum Tapered Handlebar for Motorcycles

Tapered handlebars using high strength aluminum alloys have been applied mainly to motorcycle models requiring weight reduction and high texture appearance that aluminum handlebars can offer as their characteristics. This handle bar is manufactured through extrusion processing. Conventionally used alloys had low extrusion productivity, which led to increased cost of the handlebars. In view of this, we selected an alloy securing the strength by adding a large amount of zinc while reducing the amount of the copper, which deteriorates the extrusion productivity, to the minimum adding amount, in consideration of maintaining the stress corrosion cracking resistance. However, a large amount of zinc decreases the stress corrosion cracking resistance. Therefore, in order to obtain a metallic structure favorable to the prevention of stress corrosion cracking, the mandrel extrusion was applied for the pipe manufacturing method, and heat treatment condition and swaging condition were optimized. With this development, we have made it possible to manufacture the tapered handlebar made of high strength aluminum alloy with less weight by 20% and with lower cost by 30% than those of the conventional handlebar.