Slowly getting somewhere …

Back from a long summer vacation I finally got back into working on this, with the deadline for the thingiverse windcraft tech challenge pressing me. The good news: I’ve finally found the design fault that made the wind wheel so problematic while slicing — the rendering quality of the linear_extrude command with tilt=50 greatly increases by not only increasing the number of facets ($fn=50) but also using the „slice“ parameter. While I have absolutely no idea what this parameter does exactly, neither do the authors of the OpenSCAD Manual, where it simply states: „The slices parameter can be used to improve the output.“ Well, setting slices=100 did it for me, so while not precise, the manual is obviously right. Because theres only a thin surface touching the bed, a raft is in order. Also I increased the brim surrounding the wings, to give it more stability during printing. The result is this:

wpid-20150729_162435.jpg

On another note, I found someone aiming for something similar as I do — a wind bubble machine, published on thingiverse on July 1st, shortly before my vacation. It looks cool and the idea with the gear design is charming; I’ll try it out when I have time, but won’t bother now as it will be quite some printing and I did not find yet any fotos or videos of it working under real conditions. As of now, I will not go for such an, admittedly beautiful, design, for the following reasons:

  • I found out by now, that the resistance of the fluid actually is a problem, and this will probably increase with the teeth of the gear going through the liquid; this may be neglectable because of the mechanical advantage of the gears, but I would like to go without
  • with the bubble rings being inside the gear, you have less room where the bubble fluid is actually effective, so you have to refill more often
  • while having the fan mostly in front of the machine gives a compact overall footprint, it shields a lot of the travelling way of the bubble wheels, probably reducing the amount of bubbles produced during one turn of the wheel
  • the tank is not done with bicycle usage in mind and will definitely spill its liquid after a few meters on the street; so it may be fine for the garden, but not for my purposes

So I’ll continue with my tooth belt approach. As most people don’t have tooth belts at hand, I will also evaluate a rubber band or similar things.

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