I am developing a helical compression springs simulator and I came across a doubt about the mass calculation. According to the autodesk publication, it should be calculated by the formula bellow. Although, one of the terms of it, the one besides π, have a writing that wasn't mentioned on the variable chart. I have a guess that it is the wire lenght express bellow, but if someone could tell me which variable is this, I would be very greatfull.
The publication link:
