Method for making bicycle crank arm

A method for making a bicycle crank arm of a bicycle, comprising:

• (a) providing an inner frame unit which defines a longitudinal axis, and which has
• a first seat,
• a second seat which is spaced apart from the first seat in a direction of the longitudinal axis, the first and second seats defining therebetween an elongated space,
• at least one first direction reversing guide formed in or in proximity to the first seat, and
• at least one second direction reversing guide formed in or in proximity to the second seat;
• (b) winding a first bundle of unidirectional continuous fibers over the elongated space through the first and second direction reversing guides such that the first bundle has a plurality of first segments each extending straightly between the first and second direction reversing guides, and a plurality of second segments each extending about the longitudinal axis, to thereby form an intersecting pattern on the inner frame unit;
• (c) impregnating the intersecting pattern with a curable resin material to obtain an impregnated structure;
• and
• (d) molding the impregnated structure in a mold to cure the curable resin material to thereby obtain a fiber-reinforced semi-product, which has the inner frame unit therein, for the bicycle crank arm.