RE: Things are more complicated - I totally agree. My favorite part of the article is probably the belt transmission section. I wasn't sure how it was possible for a leather belt to transmit so much power. Super fun to just dig in deeper and deeper to see how it works. Even there though, I left out a lot - the material properties of leather that let it work, how they attached the belts, the problems they had with gears transmitting power (partly leading to the development of the involute shape for gears), etc.

RE: safety valve, pressure gauge, etc. - yes, there is definitely another article to be built here :). Another fun aspect is safely starting the machine, warming it up appropriately, flushing water from the system, and the bigger engines even had a small engine to get the wheel turning.