It is a well-known fact that Benjamin Franklin used so-called Leyden jars in some of his early experiments.  Yet rest assured that I have NO INTENTION WHATSOEVER of going out and actually flying a kite during a thunderstorm, just to see how much voltage I can build up on this thing.  Nor should you even think about that one either.  O.K., it's alright to think about, but PLEASE stop right there, if that is what you are thinking.  Widespread reports hold that many people have been killed trying to duplicate Franklin's famous results.  So just because it is possible does not mean that anyone should try.  

Yet what about other possible sources of static?  Maybe a crystal radio with no tuned circuit, just a very high voltage diode and a long wire antenna, along with this thing, which by guess and by golly should be capable of holding a charge of up to 25,000 volts, or maybe even more.

Or how about wind as a source of static buildup, somehow?

Obviously, there is yet another simple cheat.  Use a battery and a diode for an input circuit, and then thereby manually pushing on the plunger, so to speak, charge will be forced to flow into the capacitor, as its capacitance increases.  Then, when the plunger is released, the voltage will have to increase in proportion to the inverse of the decrease in capacitance, i.e., according to the relationship V=Q/C.

So, there are lots of possibilities, none of which are likely to have any practical use, of course.  But, hey, this is Hackaday, and who knows, maybe some kind of mechanical variable capacitance-based voltage multiplier could be useful for something.  Then, what if only it could be made recursive somehow? Is that even possible, as if one could make a wind- driven Van De Graff generator, or something that might perform a similar function with a really efficient charge pump.

Right now, I don't have a clue.  But the thing does look nice as desk-top distraction.

Maybe I could add solar power, and a 555?  I mean, sure - why not?  As long as I can find a suitable "green energy source", then yeah - why not try to find out just what the highest possible voltage that I can get onto this thing?  Yet, obviously, there are other possibilities, given enough resources and imagination?

I mean, just take a look at how one of these things actually works, since it is, after all, a "vacuum capacitor".  The integrity of the vacuum seal is, hopefully, maintained by the use of an internal copper bellows.    Now, obviously, there might be some completely useless hacks here that would probably lead to the unwanted destruction of the device, so we won't actually be doing one of those, but it is interesting to think about some things anyway.  Like, if a lathe, mill, and other machining technology were available, and if someone could replace the piston from an old gasoline-powered lawn mower engine with a suitable vacuum capacitor, i..e., by working out a suitable connecting rod interface, then the big question would be "how many RPMS could be put on one of these, and for how long - before failure?"  

Now obviously, I am not planning on doing that.  Yet it might be an interesting digression, as an alternative to some other reprehensible monstrosity, like wanting to build a wind-powered Van De Graff generator!  And just who is going to build that one?  Well, to misquote an excellent quote from a wonderful book entitled "The Stinky Cheese Man and Other Fairly Stupid Tales", "NOT I SAID THE LITTLE RED HEN!"

Of course, if I had let's say 100 or more of these, maybe they could be used to make some kind of "Dance Dance Madness" PS2 keyboard, along with light-up dance floor.  I mean it is at least theoretically possible, but way over budget.

Then again, I remember back in the days before the COVID, when one of the local casinos in Reno offered "Live Band karaoke", while another...