Current rating for busbars

How does one go about calculating the current rating of self produced busbars?Store bought wires are a lot easier, as they have the derating factors for parallel wires and ambient temperature readily available (e.g. Radox: the manufacturers just come to these conclusions through testing?I know there are a lot of factors playing into this, but am just looking for a ballpark estimate. This link is useful, but is for wires and not busbars. Will there be a meaningful difference...Read more