Method of forming a frame joint structure

摘要

A seat frame assembly of a motorcycle has upper and lower pipes made of an aluminum alloy and having a rectangular cross-sectional shape. The upper and lower pipes have front ends constructed as joints, and solid spacers made of an aluminum alloy and having a cross-sectional shape substantially identical to the rectangular cross-sectional shape of the pipes are fitted in the joints. Flat side walls of each of the joints are sandwiched between flat electrodes of a resistance welding machine, and pressed and heated so as to be crimped on the spacer while an electric current is flowing between the flat electrodes.