Calcualting Chain Requirements (25 v 35)

[psquared89]

Now, before people bite my head off for not searching this topic, I have, but none of them answer my question. In reading CD I have found quite a few threads about what size chain should be used, and the common theme is engineer it properly or don't do it at all. There has, however, been little discussion as to how to 'engineer it properly'.

I'm looking for some cold hard math, somewhat like this post, but more coherent. Please, feel free to speak math to me, I've completed AP Physics and am currently in Multi-Variable Calculus. If anyone understands how these kind of calculations work and how to explain them, or could point me to a resource where I could teach myself that would be greatly appreciated.