Admin Note: I split this topic from the
Turbine Top thread
++++++++++++++++++++++++++++
This post was inspired by Dalton Bissell's "turbine top" at
http://www.ta0.com/forum/index.php/topic,4197.0.html -- a fascinating idea beautifully executed! All of Dalton's tops on Shapeways are elegant and clever, but the turbine top's
definitely on my shopping list.
Having no fabrication skills to speak of, I design LEGO tops -- hundreds to date (see
http://www.moc-pages.com/folder.php/188421). One big advantage to the LEGO medium is the flexibility to go way outside the usual top design box, and I now see from Dalton's work that 3D printing does exactly the same.
Tank Top (rotor ring from inverted LEGO tank treads)
Tops with ring-like rotors have long been a favorite genre for me, both for the visuals and the performance.
As Dalton clearly knows, in top design, you can generally either fight the aerodynamics or turn them to your advantage. Here, Dalton managed to do both while capitalizing on the wagon-wheel effect due to the spokes. Bravo!
Made the simple "Znap tops" below over a year ago from some cool-looking LEGO plastic wheels from their long-discontinued Znap line. (Details at
http://www.moc-pages.com/moc.php/422867.)
https://www.youtube.com/watch?v=fGlb-8GEoycI was aware of the aerodynamic potential of the airfoil-shaped spokes at the time but dismissed it as insignificant on finding that the direction of spin had no effect on spin time -- even at 4,000 RPM or so. (The thinking was that spinning them in the lift-generating direction would de-weight the tips, thus reducing tip friction, but no go.)
However, I
never thought to blow down on them from above until I saw your video. Sheer genius!
Well, I just now put the Znap tops under the wife's hair dryer, and behold! The large ones work quite well as "turbine tops", but the small ones do nothing for lack of swept area at the blades. The large ones self-start under the dryer, can be re-accelerated while spinning, and can even be followed around with the dryer and steered by it! They even show a slight tendency to self-center within the air stream.
Don't worry -- these large Znap wheels are very hard to find now.
Video to follow. Much to be explored in this new "turbine top" genre you invented. Very excited.
BTW, the spokes on the large Znap tops also generate nice wagon-wheel effects. The effect is especially dramatic under overhead LED lights on a standard pulse width modulation dimmer.