Hi Prof Jones and People,
No theory. I wish I had one. Perhaps have I some clues?
I'm wondering whether this is not just a matter of mechanical resonance
and standing waves?
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Actually, with mechanical resonance Tesla could perform amazing things. Could he not?
For ex:
Tesla's oscillator:
http://en.wikipedia.org/wiki/Tesla%27s_oscillatorNikola Tesla's Earthquake Machine:
http://www.excludedmiddle.com/earthquake.htmMainstream Science does not consider resonance as 'OU'. My (poor?) common sense does not agree.

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In fact, we have at least 2 frequencies.
The freq of the grid - the "prime mover"?- (60 Hz for USA and 50 Hz for Europe, for ex.)
The main freq of one cup.
In the Savic's Sonic Boiler (SSB) the ball does not really vibrate and seems to act as a kinda "wall". IMO. In the Prof. Jones's Sonic Boiler (PJSB) we have a second "cup" that is really vibrating also.
My take is that the main freq(s) of the cup(s) should be integer multiples of of the grid freqs.
50: 100, 150, 200, 250, 300 ...500 ...
60: 120, 180, 240, 300, 360 ...600 ...
Now, perhaps, some Intermodulations and cross-modulations would do the "mechanical resonance" job?
http://en.wikipedia.org/wiki/Intermodulationhttp://users.tpg.com.au/users/ldbutler/Intermodulation.htmThe difference between intermodulation and cross-modulationhttp://www.edaboard.com/thread23049.htmlNow, have the main freq(s) of the cup(s) to precisely match the previous numbers?
I dunno. Perhaps one secret is that inter/cross modulations could give some low earth freq (about 7 Hz). In that case, and without strong theory or fortunate luck ('mojo') huge COPs would be out of reach???
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About standing wave and according to what Prof Savic could had scarcely and 'cryptly' disclosed: I might have found a relation between the "gaps" between the 2 part/electrodes of a sonic boiler.
In some pictures of his "empty beer can sonic boiler", prof Savic gave very accurate mysterious gaps: 2.1 mm and 2.52 mm. BTW, he also gave a gap of 1.725 mm

Should come from any other calculation.
If the speed of sound in boiling water is 1512 m/s
According that:
Lambda = V / F
Lambda (meters) = wavelength
V = speed (meters/ seconds)
F = frequency (Hz).
Should you consider 1/4 wavelength.
Lambda/4 = (1512/(60 * 300)) /4 = 0.0210 m = 2.10 mm
Lambda/4 = (1512/(50 * 300)) /4 = 0.0252 m = 2.52 mm
Multiplying freqs does not make sense to me.BTW: 2.10 mm gap was given for Europe (50 Hz) and 2.52 was given for USA (60 Hz).
Pictures from Prof Savic are here:
http://jeanyves.hervouet.free.fr/NDS/Speculations.htmlNo comment = I will shut my Big F' Bl' Froggy French Critical Nasty Derisive Mouth.

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Now, People, please, make your own theory...
The principles, most of time, are very simple. The results can, of course, be very very complicated.
For example: you can design a black and white table plotter 2D software with just 3 basic instructions.
- Pen Up
- Pen Down
- GoTo X,Y
Very Best,
Jean