Originally Posted by
reefraff
http:///forum/post/2519082
On the balloon thing and this works basically like the reverse carlson. The ballon is zip tied to the rigid airline. that is what feeds the air into the balloon. You put the balloon into the PVC and that unit mounts under water.
Ah, that's the part I was missing, and suspected.
When the balloon inflates it displaces water with air. It would be like placing a gallon milk jug full of air in your tank and pushing it below the water line. The Reverse Carlson setup just uses air instead of a bladder (Balloon).
But how does it move a large enough quantity of water fast enough? Wouldn't the balloon's deflation be limited by the size of the airline tube?
This is actually the main engineering problem I've been playing with: it's easy enough to slowly displace water or suck up water into something. The hard part is finding a way to quietly open a large enough aperture to the open air suddenly enough that the water can rush in or out with some force. Mechanical parts could work, of course, but they often fail in unpredictable ways. Toilet flappers are another common possibility, but they are also imperfect. The reverse carlson is an engineering win precisely because it manages all of this with no moving parts at all. It's just really, really noisy.
