Well after all these years no one has come up with a cell to produce HHO Efficiently and lots of gas.
You need to have something that anyone can build and it works, so my take on all this is it is the challenge not to do it to run your car on it, as now electric cars seems the way to go.
The other thing to me is that most draw a WFC with a positive and negative just like a electrolytic capacitor, well that is where you are wrong it can act as a capacitor but as a non-polarised one. Then again it is not like a battery, or you would have separate petitions with the two plate and the electrolyte in between, but a battery has a mix of acid and water for reaction to the lead in the plates.
So the WFC the tube type may have one singe tube with a solid rod down the centre.
Two tubes one inside the other.
Then with one tube with the water in it you have a single cell, with just plain water or distilled water, rain water is better than tap water.
The car battery cell with the mixture has a low path of resistance between the plates to some extent.
A WFC has high resistance between the two anodes, the closer you get tem the resistance gets lower, but to be technical with water in this situation you have resistivity.
So you will have to force an ion exchange path for the voltage and current to pass from one anode to the other.
You all have been using a series circuit to try and do this, to me the best way is to do this is to use a parallel circuit.
You can use plates if you want to but this is again much the same challenge. I had what is known as a circular cell I still have the design somewhere but it was for a cell that used powdered KOH mixture.
To work all this out correctly you need the volume of the cell, how many tubes and what type the length and diameters the height and diameter of the cell.
Then you would need to measure the capacitance of each tube while it is immersed in the water. And if you can the DC resistance, if not then go for the reactance using a meter to do that. What power supply do you intend to use, and how you are going to apply it.
As in just positive going square wave 50/50 and at what frequency? Are you going to try and use a PWM.
Myself I would use a push pull circuit I will if you a really interested I will draw up what I think it has been a long time
Ask the question first
What are you trying to achieve?
Do you really care if it is not plain water to get a lot of HHO?
Or is it the challenge just to see what you can or if you can get HHO from water in a big way?