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Comment by radarsat1 | Hacker News Reader

One of the unexpected pleasures of having a 3 year old has been learning far more than I ever planned to about steam locomotives. It turns out steam engineering is fascinating, this article emphasized it for me even more. It really amazes me how much ingenuity there is in just connecting the right shapes and joints up so that the right thing happens at the right time, creating perfect cycles, regulators, etc. Seeing it explained in an iterative way like this is fantastic because you can understand what problem is solved by each part. I would love to see a piece like this strictly about locomotives.

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One of my treasured toys - probably from a few years older than your 3 year old though - was a rocking cylinder steam engine my father gave me. It was a present from his father as part of a steam powered boat they built together probably in the late 1940s.

And you can still get them reasonably inexpensively: https://www.aliexpress.com/item/1005007964198565.html

I bought one for a friend's 5 year old a while back and became BEST UNCLE EVER!

The run well on compressed air (like an electric car tyre inflator or small air compressor), or for a bit more high temperature danger they run great attached to the steam wand of an espresso machine. When I was a kid dad built me a steam boiler out of a steal aerosol can and some copper tubing with a folded brass sheetmetal alcohol burner. That's not a 5 year old friendly thing though, from memory I'd have been maybe 10 or 12 when he started letting my light alcohol on fire in that garage or backyard. (Modern parenting may disapprove...)

Thank you! I have a few ideas for the next article. Locomotives are up there on the list, but they are the final challenge of steam engineering, there is so much to cover.

Also considering the origins of precision - the intertwined evolution of machining tools and measuring systems that allowed these machines to be built.

RE: 3 year old - yes, mechanical systems are wonderful for children (and adults). There is something incredibly satisfying about watching them in motion doing work.

High performance "modern" steam engines are fascinating, they're not necessarily simpler than their internal combustion successors, just different. Monotube boilers create superheated steam that pushes 1200°F, which is right around the same temperature as the exhaust gasses in truck's diesel engine pulling a large hill at maximum power. Hot enough to melt aluminum save for the presence of oil jets to cool the piston and a jacket of cooling water surrounding the cylinder. However, since there's no combustion happening in the cylinder of a steam engine, you don't have any cooling water surrounding it--that would be totally counterproductive. So steam engines operate in a thermal regime that is far more extreme than internal combustion engines. Consequently, bores are often cut slightly tapered to account for the temperature gradient across the stroke, in a double acting engine the cylinder bore has a slight hourglass shape, otherwise the thermal expansion would cause the piston to bind at the ends.

For a fun rabbit hole to dive down, check out Doble steam car technology or the Besler airplane engine.

Thanks for the pointers! That is an area I've not explored much - reciprocating steam using modern technology. Using modern electronics, sensors and valves to optimize steam expansion would be a fun project. Perfect cutoff every time :).

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