多年来载重型28″自行车前叉,使用的叉肩大多数是永久51型的斜肩式,叉肩材料厚度2.5mm,B_1～_2F 冷轧或热轧板料,结构形状如图1所示。这种结构的下口与立管配合面较长,增加了立管与叉肩装配钎焊面。其缺点是图示粗线部位,下卷口两侧凹处, Over the years carrying 28 "bicycle fork, the fork shoulder used most of the permanent 51-type oblique shoulder, fork shoulder material thickness 2.5mm, B_1 ~ _2F cold-rolled or hot-rolled sheet, the structure shown in Figure 1 . This structure of the lower mouth and riser with a long surface, an increase of riser and fork shoulders assembly brazing surface.The disadvantage is that the thick part of the map, the mouth on both sides of the recess,