I am working on project involving designing a recoil spring coil of diameter 10.2 mm and wire diameter 1.25 mm. I tried using a solid core wire but it failed due inadequate tensile strength. Dimensions can only be altered by 5 mm, which is not sufficient to make the solid core wire work.
My professor suggested looking into braided wire rather than a solid core wire. I considered 6x7 wire rope but they are too big. After some googling, I found out there are recoil springs with braided wires with 3 strands. I know it is going to be somewhat less than 3x the strength individual wires. I searched handbooks, reference books, etc. but I could not find any established relations/formulae between strands and tensile strength. How can I determine the tensile strength of a braided steel wire based on the number of strands?