I would wonder at not using a component like a BAT54 or a BAT46 diode in the capacitor switchng ciecuit. At about half the forward voltage drop the output voltages achieved can come closer to the hoped for 2X value one strives for in these "voltage doubler" circuits.

One reason chips like the '7660 work so much better is that the switching activity is done with MOSFET switches instead of diodes. The drop across such switches is less than diodes and thus one can attain output much closer to the ideal of 2X the input voltage.

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Ha Ha Ha....I am one of the "fathers" that used 555 chips for various things when they first came out. It was used rather heavily as I recall in a pong game I made that operated as an anlogue device with ball position being the voltages on two capacitors. In that day others made basic pong video games with boards that had huge collections of digital gates, counters, and flipflops. Mine was a huge collection of 555s, comparators, opamps and oneshots!

Michael Karas