> The tech necessary for steam engines They had basic concepts but could not have produced a steam engine that did useful work. The Archimedes device you ment

> The tech necessary for steam engines They had basic concepts but could not have produced a steam engine that did useful work. The Archimedes device you mention (the aeolipile) was basically a kettle mounted on an axle that did indeed spin. But it had no way of building up pressure to the degree necessary to move something other than itself. The Romans probably didn't have good enough materials tech to build vessels that could hold sufficient pressure to do useful work. Early steam engines could explode catastrophically and they were built by cultures that had centuries of cannon-making experience behind them. The Romans also lacked a compelling application that would have driven tech development and didn't have the iron/steel/coal industry required to build railways, etc. It's telling that the first commercially viable steam engines were basically water pumps for getting water out of mines, and it didn't matter if they were massive and underpowered. It took another 60/70 years for the tech to improve enough to power vehicles.