Bruce Yeany produces many excellent science videos - this explains the "Magic Fountain" far better than I can.
In the video, he suggests that you can make one at home by just using 2 soda bottles and taping the caps together. My original implementation was basically the same - but it easily broke at the first show when demonstrating it. Someone picked it up "wrong" and the caps simply came apart. (They picked it up by the empty bottle and, well, the bottle filled with water simply fell off.) After that, I started using Orange Juice bottles because they have much larger caps. For each new generation, I added more bolts. It turns out that it requires 4 to keep the seal from separating and to reduce the possibility of breaking the caps when the assembly gets dropped on the floor.
|Note:||Basically, kids do not understand weight distribution and torques. As a result, they frequently pick the assembly up "wrong" and/or set it down off balance (all the water - weight - is on top when the fountain starts). This is why I need to bolt the caps together and why the parts need to be replaced on a regular basis.|
In the video, Bruce presents two methods to make the holes in the straws - a drill and a pair of scissors - I just use push pins used to stick notes to a bulletin board. Based on experience, when the holes are too large, the fountain will not work. But, since straws are cheap - just experiment :)
The biggest challenge is to keep the assembly from leaking. I have tried - hot glue (does not stick), bathtub caulk (also does not stick), o-rings (good until the plastic deforms), custom washers inside the caps, and electrical tape (just slows the leaks). Most of these appear to work .. until the first time someone drops the fountain on the floor. That normally happens several times during a show. Of course, your mileage may vary.