First, thanks. Second, please excuse me for going all geek here. For those of you who are sculptors and painters.... I'm letting my inner engineer show here....
If only... a guy can dream, can't he?
I've actually spent many an hour trying to work out exactly such a concept. I think that before we can print a working steamer, we will be able to print in-situ electric motors that accomplish the same effect.
The operative word here is "tiny". At this time, the required clearance (in FUD) for moving parts is 0.05mm, but I have found that to be more like 0.1mm to keep them from sticking together. One tenth of a millimeter is an excellent tolerance gap if your piston face is 10cm or even 20cm in diameter. But, when the piston face itself is only one millimeter in diameter, then 1/10mm gap is huge.. the gas would leak around the side and most of your pushing force would be lost. Even if you had a multi-material printer that could print the rubber gasket to seal the gap, the existing printers just don't have the resolution to make "tiny" pressure cylinders yet.
I am excited to see where this 3d print technology is going to go over the next years. I can easily envision a future where we can print working model trains in-situ. I just need for the print technology to catch up. I think that before we get high enough resolution to print gaskets, we will be able to mix plastic with metal, and thereby make working electric motors. An electric motor can be rather simple.. it can have some pretty big gaps. We just have to be able to mix materials.
There's nothing I'd love more than to pay homage to those guys who designed these massive "big iron" steamers over 100 years ago.. with a working model 25mm long <GRIN>