Vibration-powered pot legs lift it off the burner when the bubbling gets too intense. Set the dial to control how much of the roiling energy is transmitted to the oleos.-- FlyingToaster, Jun 11 2013 If this doesn't yield two and a half parboiled croissants, there's no justice. [+]
Second premise: there's no justice.
Conclusion: ... umm, P, or not P.-- pertinax, Jun 12 2013 // the roil energy is transmitted to the oleos //
How?-- BunsenHoneydew, Jun 12 2013 Just thinking up a possibility, not the only one by any means, but I figger there oughta be at least one answer for BunsenHoneydew (who I haven't seen on here since halfway back to the last cicadas, seems like; How ya been!?):
Boiling happens when a small bit of water near the heated surface (bottom) of the pan suddenly converts to steam; this makes a bubble which is much less dense than the water, so it rises. But if the water is cooler, then the steam condenses again and the bubble collapses back on itself.
Now imagine there's a perforated plate / grid / mesh / something at distance x (pick it, doesn't matter yet; in practice, it might, but we're busy theorizing so don't bother me with practicalities right now) and the bubble forms at the bottom, rises to the plate, the plate steals heat, the bubble collapses. So, the volume of water under the plate had to go down when the bubble formed, and go back up again when the bubble collapses. The water isn't compressible, so there has to be some flow between the area above the plate and that below. That could be captured with some sort of reciprocating action.
When you get closer to "boiling over", the water under the plate could boil away, robbing us of our working fluid just when we really need to get those legs working. I'll think some more.-- lurch, Jun 12 2013 I read this as Baba Yoga Crackpot and was pleasantly surprised. I like this one.A bi-metallic coil could be used to raise and lower the legs as well.-- 2 fries shy of a happy meal, Jun 12 2013 //How?//
There are plenty of vibration-powered mechanisms: most are piezoelectric in nature (reverse buzzer device), a few are mechanical (like an automatic watch). This would be the latter, each leg having its own power source.
The pot initially rests on its base as well as the legs. Since the burner stand dampens the vibrations somewhat, the lifting motion takes a bit to get going. This is a good thing, since it also takes awhile before a bubbling pot of liquid accumulates enough heat to start boiling over.
When it "lifts off" the roiling vibrations, undampened, will increase quite a bit. It will continue to rise until the equilibrium of dial-setting vs. roiling-intensity is reached, typically say a couple of millimetres to centimetres off the burner.
(It will also clatter against the burner stand as it lifts off)
As a sidenote, since the legs are powered independently, the heat is more evenly distributed across the base, since a leg closest to a hot-spot will end up ever so slightly more extended than the others, in equilibrium.-- FlyingToaster, Jun 13 2013 random, halfbakery