VE>Please send me some background on this. It reminds me of the "cubic Archimedean screw": http://rsta.royalsocietypublishing.org/content/354/1715/2071 Paywalled? http://archive.msri.org/about/sgp/jim/geom/level/library/elser/animations/in... Veit I noticed the 2D geometry in high school ~1960, after seeing Wankel stories. ~1965 I showed Marvin Minsky a PDP-6 animation (using Minsky circle algorithms, of course), and he suggested the helical twist. I then suggested varying the twist along the length to get an arbitrary Diesel compression profile, and added the idea of porting by continuously deforming to circles via four-point "ellipses". It is positive displacement. Six rotors can pump two volumes with zero net pulsing. (Neat proof.) N rotors can pump N-ε volumes. I've long wondered if a sheet of slippery rotors could be driven just at the edges to make a forceful, high volume, low velocity, low turbulence blower. A subsequent patent search showed the 2D idea in 1943, with a kludgy scheme of channels through the rotors. A later patent had the helical twist idea and the four-point "ellipse" idea, but not the continuous deformation, so it needed a quadricuspid plug running the length. Closer to your cubical screw idea might be this geometry <http://gosper.org/wellpump.gif> with non-parallel axes. The rotors are shown hollow, but all save one would likely be solid. You might put it at the bottom of a well to force fluid up a pipe through the hollow rotor. The rotors <http://gosper.org/wellrotors.gif> are bounded by Lissajous curves (with fairly nasty formulæ) twisting while radially projected. These last two stills are from old Macsyma animations (which make things much clearer). (Its bizarre last owner shut Macsyma Inc down before they implemented animation exporting.) --rwg On Mar 18, 2012, at 10:01 PM, Bill Gosper wrote:

To run it <http://gosper.org/pumper_2.mp4> continuously, download with> Miro, QuickTime-View-Loop.> The pumped shapes split lengthwise resemble boats, so a grand entrance> to a math museum would be a chain of these boats in an annular canal,> passing through four rotors acting as an (approximate) air|water lock,> with another four for the exit. Oh, the insurance.> --rwg> No manual entry for overboard