| Know anyone with a machine lathe? Buy a length of 3" aluminum, chuck it up, bore a 2" hole down the center. Now set up a 1/8" parting tool, plunge in 3/4", pull it out, dial over 1/4" and plunge in. Lather, rinse, repeat. Very tedious, but slick and custom made.
Obviously diameters can be different, plunge accordingly. You can probably go deeper grooves if in a low pressure setup (as explained is 1/4" wall thickness, 1/8" would be fine, maybe even less). Also, taking a nice even cut across the length first and then polishing with 320 grit paper will make a nice semi-polished-not-quite-brushed finish (I'd do this before the plunge-cutting of the grooves).
Wanna get really technical, use a four jaw chuck and off center the part. Bore a 7/8" hole down it. Now, chuck it off center the other way and bore a second 7/8" hole. Follow above procedure for increasing surface area. Cut threads on the last 1.5 inches, and make a hollow endcap to fit (with really shallow grooves to maintain the look). Now you've got a dual pass rad-tube (tuberator? nah, that sounds like a potato fridge). I've been wanting to build a set of these for over a year, but since I haven't started yet, I might as well share the idea. If you use it, lemme know how it works (I may decide to forget I ever had that idea if you don't have any luck!)
For the stuff you attached pics of, try a local hvac repair center. They may have leftovers in the scrap bin, or be willing to sell you a short section. |