> Clearly steam engines require good metallurgy If we ignore the ‘minor’ issues of efficiency and longevity which would ‘only’ affect how practical the device

> Clearly steam engines require good metallurgy If we ignore the ‘minor’ issues of efficiency and longevity which would ‘only’ affect how practical the device would be I am not sure about that ‘clearly’. So, let’s ignore all practical issues, and just try and build a steam engine that would provide some power for a decent period, ignoring efficiency. Tensile strength to prevent pipes and the boiler getting torn apart by the steam pressure would be a main problem, I think. There’s https://en.wikipedia.org/wiki/Wooden_cannon https://en.wikipedia.org/wiki/Wooden_cannon: “Wooden cannons have been manufactured and used in wars in many countries. The wooden parts were invariably strengthened with metal fittings or even rope.”, and (from World War One) https://en.wikipedia.org/wiki/Albrecht_mortar#Design https://en.wikipedia.org/wiki/Albrecht_mortar#Design: “The Albrecht mortars […] consisted of a muzzle loaded smooth bore barrel built from wooden staves and wound with galvanized wire for reinforcement” Those likely didn’t work for long periods, but they did withstand fairly high pressures repeatedly. So maybe, a boiler and pipes built with wood or bamboo, strengthened by rope could be made to ‘work’ at relatively low pressure for a while. I would try to line the piping on the inside with clay to prevent steam from weakening the wood. Next major problem: wood catches fire relatively easily. That’s at about 250°C, though, so there’s a range (about 520K vs 370K or 40% of room) at which steam can be created, but wood doesn’t burn yet. Water boils at higher temperatures at higher pressure (https://www.engineeringtoolbox.com/boiling-point-water-d_926.html https://www.engineeringtoolbox.com/boiling-point-water-d_926...), but that need not be a showstopper. The Newcomen engine doesn’t run on high pressure. It also provides a ‘solution’ for another major problem, that of sealing the cylinder to prevent steam from getting out. https://en.wikipedia.org/wiki/Newcomen_atmospheric_engine#Technical_details https://en.wikipedia.org/wiki/Newcomen_atmospheric_engine#Te...: “The piston was surrounded by a seal in the form of a leather ring, but as the cylinder bore was finished by hand and not absolutely true, a layer of water had to be constantly maintained on top of the piston.” So, I suspect you could build a steam engine without metals. It wouldn’t be efficient and would be prone to catching fire, though.