Resistance soldering

[petermoblin]

Would anyone happen to know much about resistance soldering? Been thinking of buying one for a trailer build I have planned and not sure which unit to go with. The trailer will consist of a lot of 1/4'' brass square bar and not sure what wattages I should be considering to produce enough heat to properly solder the joints. I've searched google and everything that comes up is trying to sell me a unit or telling me how it works and no wattage to material size ratio.

I will continue my web search for info, just thought I'd ask around here. Hope to hear from some of the great minds on here and all input is appreciated. Thanks