The length of the chain is actually the diameter of two small circles plus the distance between them. Have I made myself clear? Because you can't send pictures until the second level. So I can only describe it. The length of two chains is 2.5*2-0.8. And so on, three are 2.5*3-2*0.8. Section 50 is 2.5 * 50-0.8 * 49. (* _ *) Hee hee ... ~