This is a recent TIG Welding project of mine for someone who welds his own Inflatable surfing mats in the UK. Google ' G Surfmat ' for more piccies.
The bar sits inside a giant soldering iron, the whole thing is made from 6000 series magnesium alloy, when the iron is on heat is rapidly transferred through the aluminium to the wheel which is then pushed along a jig like a giant pizza cutter. The heat from the wheel then welds the mat seams. There is a .25mm gap everywhere to stop the wheel sticking when hot.
Apparently these are normally fixed discs and you rock the welder as opposed to a moving wheel.