bling and tasteless jokes, we would be attempting to channel Maxwell’s demon. They went for it — though they insisted on keeping the tasteless jokes. Using segments of iron plumbing pipe as the hot and cold sides, I suggested that we epoxy together a vortex assembly with three ½" slices of a Delrin plastic 3" rod.

Revised Approach

The guys are not scientists or machinists but they are talented, creative folks that are deeply interested in how things work. Hoping that would be enough, the group reduced the vortex assembly design to use a single Delrin disk. In my original plan, the washer was replaced with a ½"-thick slice of Delrin, but the revised plan brought back the washer. We didn’t know if the thicker Delrin disk would affect performance, but since we had no idea what we were doing, we decided the fewer changes, the better.

The finished vortex tube looks like a champion! From appearances, it would seem to instantly freeze tissue samples for plague research or, perhaps, cut 1"-thick steel plate with an awesome 1,000-degree cutting flame! Real life offered slightly less spectacular results, but we did measure a temperature spread of 8 degrees between the hot and cold sides. We raised the flag and declared victory!

If I were a real scientist, I would continue to refine the design using our modest success as a starting point, but as an amateur, I am happy with the Proof Of Koncept/Experimentation Revue results. Until an engineer shows up with some imported spicy salami, the vortex tube will sit on the shelf as a memento of a fun late night with good friends.

Mister Jalopy referenced C.L. Stong’s collected columns from the out-of-print The Scientific American Book of Projects for The Amateur Scientist, but the complete, 72-year archive is available on CD-ROM (Scientific American’s The Amateur Scientist, Science Fair Edition, $30, brightscience.com).

AiRTX International ( airtxinternational.com) sells commercial vortex tubes capable of generating temperatures from - 40°F to 250°F. We thank them for allowing us to use their superb illustration.

Mister Jalopy is an earnest but amateur scientist. Know more about vortex tubes than he does? We wouldn’t be surprised. Join us for vortex discussions at makezine.com/09/ vortex_tube, as we have lots of questions.

36 Make: Volume 09

Despite being hoodwinked, my friends met the vortex tube challenge with enthusiasm and a determination to succeed, provided the beer did not run out.

In the original “Amateur Scientist” design, adjustments are made via the stopcock on the hot side and the interchangeable washer on the cold. (Source: The Scientific American Book of Projects for The Amateur Scientist, C.L. Stong, 1960)

Cold Air

- 40˚F (- 40˚C)

Compressed Air In 70˚F ( 21. 1˚C)

Hot Air 230˚F ( 110˚C)

Control Valve

AiRTX International, LTD. 2005 ©

AiRTX International’s commercial vortex tube ($109- $149) produces frigid air from room-temperature compressed air.