This is a thought experiment that I had for a long time, and I would like to know if it is possible/feasible. Let's assume that we have a very powerful ancient emperor, who has an idea to harness the power of steam. The predications we are working from:
This is a stone-age civilization, metals are not available to them.
The Emperor is very powerful, and has access to effectively infinite slaves and servants to do his bidding.
The Empire is far reaching, and they can acquire any material they desire in sufficient quantities.
The Emperor employs a lot of scholars and scribes, and they have access to reasonably advanced mathematics, and anachronistic solutions - basically they are far better mechanical engineers than they should be.
Ideally, the engine should provide an economic advantage, but that is not the goal: If we can make a good cup of espresso with it, that is considered a success.
We will need the following parts:
A boiler, that can withstand high pressures, and can be refilled with water.
I have seen pressure cookers made of clay, so I suspect this can be used. I don't know if there is a practical limit to the thickness of clay pots, they can be probably made as thick as bricks.
Alternatively, a block of stone can be hollowed out - this would be harder to handle.
A valve that can be manually released, or automatically releases after a certain pressure is reached.
My first idea was a leather balloon/tube, that has a weight on it. When it builds up enough pressure, it lifts the weight, and that releases excess pressure in a kind of self-regulating manner. Basically imagine a garden hose with a block of stone on top of it. Instead of leather, it could be made from intestines, as those were succesfully used in airships. Maybe there is a kind of fabric feasible too? Here is a quick sketch with MS Paint:
The other idea is to have another hollow stone (or even a pre-existing stone chamber can be used) with one exit on the top, that has a heavy plug in it. Similarly, given enough pressure, the plug is lifted. It can even be housed in a tubular structure, making a primitive "piston".
- Some way to connect these elements. Since we can't machine/cast/forge metal parts, this is considerably more difficult.
If we are going with clay pots, and leather bags, the top of the pots can be notched, and we can tie the leather tube on it with minimal leakage. Connecting stone parts is a bit trickier - we need to make surfaces that are flush with each other, and don't leak (too much) pressure). If we have a less than ideal fit, we might want to put the vessel containing the water at an angle, so the steam building up doesn't knock it off. Then a pressure chamber, with all the devices can be fitted on top. Another sketch:
If this works, and produces steam as desired, the only question left is to how to harness it. I imagine pushrods and wheels would work just fine if made from wood, and a coffee filter can be made from clay, or even some fabric.
Edit: Edit2: single question Clarified, actual questions:
- How much steam could any of these designs generate? (as in: none, enough for a coffee machine, or enough for machinery)