Designing the first version of the wind wheel, with bubble wands directly attached, given my lack of experience with OpenSCAD, was surprisingly simple and took 30-45 minutes. While there are plenty of wind wheels out there to download, nothing seemed to really it and I decided to do a simple linear_extrude, with a twist setting. The result looks nice:
For the shaft I used 2mm welding wire, one that comes in rods rather than as a roll, which worked fine. I printed a few small rings that could be pressed on the wire, to hold things in place. The whole thing is supposed to be attached to this bubble liquid tank:
And so, the same day, my first prototype:
Let’s be honest: it does make (a few) bubbles facing a fierce wind but we certainly can get better. Mostly this thing spills a lot of liquid with every little bump on the street. I learnt, that while having the wands directly attached to the wind wheel makes things very simple, my first design has some obvious and serious disadvantages to it:
- My printer’s build space will only allow for a certain size (in the case of my Kossel mini up to 170mm diameter, damn I’ll have to win some professional machine in a contest!). This means that the size of my bubble wands has to be substracted from the size that still is available for our wind wheel. If you take a look at the wheel above, it’s easy to estimate that getting rid of the bubble wands would allow me to print a wind wheel with more than double surface.
- As a consequence of 1., it’s difficult to reach a wind speed that will steadily overcome the friction the bubble wands meet in the liquid.
- As the wind wheel should not dip into the liquid, the height of the tank is limited by the size of the wind wheel.
- As a consequence of 1. (short bubble wands!) and 3. we have a very small tank.
- The size of the tank is even more problematic because we won’t get any bubbles anymore when the liquid level falls below the point where the bubble ring starts — at that point the soap won’t coat the ring anymore.
Because of 5., the tank stores much too much liquid which will never be used, which is a huge waste: because we can only make bubbles until the liquid level falls under a certain point, the following to tanks would get you the same amount of bubbles, but the first one will store a lot of wasted liquid:
But not only this is a lot of wasted liquid — it will also contribute to the problem of spilling liquid, because the amount of liquid in a simple tank will add to sloshing. That’s why in my second design of this tank I decided to go for the idea on the right. In addition, I decided to put bulkheads into the upper part of the tank to reduce sloshing effects:
On the photo you can also see a simple mount for the luggage rack of my bicycle. With this setup I was able to produce a few bubbles, but I had to get pretty fast and it still spilled much.
I now decided to drop this simple design and go for a more complex solution which should solve the problem of overcoming the friction in the bubble liquid as well as spilling and tank size. The idea is to separate the wind wheel from the bubble wand wheel.