Hey Kevn thanks for the compliment! I'd love to see other intercooler / end tank designs, especially any that are innovative.
This cooler is for a VW in an autocross racing application where the class does not have a minimum weight, and the boost pressure is in the upper 20's psi range. Weight savings in this case is pretty important (pounds or even ounces here and there can add up!), as are good performance characteristics of the intercooler (good cooling efficiency, and minimal pressure drop.)
You may be right that most sheet metal fabricated end tanks people make are out of 1/8" thick aluminum, but that may be a good idea for designs incorporating large, flat surfaces that are subjected to pressure. The flat surfaces I believe, (kind of like the base of an oiling can), flex a lot more and have higher resulting stress concentrations from the bending forces as a result, basically because they are less rigid than other shapes from holding back the boost pressure. Examples of shapes that would hold the pressure back better and more "rigidly" would be ones incorporating simple bends (IE: cylindrical or conical shapes) or even compound bends (spherical or balloon-like shapes). The simple bends take more work to form than just cutting flat pieces, but less effort than hammering out or pressing complex curved shapes. Incorporating bent shapes into the design has another benefit, of being able to better shape the air flow through the end tank, for smoother more laminar flow (resulting in less pressure drop through the intercooler.)
If you want to look at what types of fabricated shapes hold back pressure the best, take a look at pressure vessels. Notice their use of simple bends (cylinders) and compound bends (spherical shapes):
http://en.wikipedia.org/wiki/Pressure_vessel
(For intercooler end tanks, we'll of course need to use shapes that have fairly large openings for air to flow in and out.)
There is more to think about with an intercooler end tank than just holding back boost pressure however. Engine vibrations or any torquing motions of the engine moving in the mounts can push and pull on boost tubes and the intercooler (and boost tubing system) will need to hold up to whatever those motions are. Also rapid, uneven changes in temperatures might also make the material expand and contract unevenly, adding to the material's stress.
Finally, you've got to select a thickness that you are able to work with. 16 gauge was just about as thick as I'd want to bend by hand on something like this, at least with my simple tools (vice, some pipe/rod, hands.) Dinging the compound radiused edges would have also been a lot harder and maybe not worked if the material were much thicker. Also thicker materials might be easier for most folks to weld than thinner materials. I was definitely on the learning curve with welding the 16 gauge aluminum here. 16 gauge aluminum is also on the thick end of what I can comfortably trim with tin snips.
I feel like I've definitely gotten better at "TIG sheet aluminum" since I started this project, and I really appreciate your helpful advice on the techniques also.
