I posted a problem I had getting excel to calculate belt lengths properly. I spent ages fooling around trying to get the thing to match real life. The drive belt on my lathe is marked"800" and the formulas produce "832".
I bought an Contitech SPZ "825" length belt for the lathe and its too small. The "800" belt is obviously not!
Anyway here for those that are interested here is an excel model, which apparently works and apart from a minor error "mike" helped with always did:
Steve