Engineering drawings of small model engines used in model aircraft making. These designs are intended for manufacturing and practical operation, rather than merely for display, and can be used to build fully functional engines.
1. https://outerzone.co.uk/plans.asp?cat=Engines&Xcardsperpage=...
2. https://modelenginenews.org/midge/index.html
> http://www.model-engine-plans.com/otheritems/JEH_Catalog.pdf
> https://modelengineeringwebsite.com/Midget_gas_engine_1.html
> https://www.adriansmodelaeroengines.com/catalog/product.php?...
> Previous submission related to model engines: https://news.ycombinator.com/item?id=46098655
Heavy water reactors (CANDU in the case of the explanation) don't scale down past a certain point - the water flow ends up with weird dead spots and that affects the reaction and cooling of the fuel rods. Since they don't scale down well enough, they aren't suitable for portable use, such as in submarines.
I'm not sure if it's still the case, but apparently one of the largest sources of nuclear engineers/scientists in the US was the US navy.
This also lead into the story about Jimmy Carter (nuclear sub naval officer at the time) coming to Chalk River in the 50s to help with the NRX meltdown...
This article scratched an itch.
https://calteches.library.caltech.edu/1976/1/1960Bottom.pdf (8 pages, PDF)
This is imo why scaling down combustion engines beyond a certain point makes little sense - you don't gain anything in terms of weight since the wall thicknesses are determined by the pressures the engine has to endure which is the same - this is why model engines suck - they're not only less powerful than big ones, but less powerful per pound.
https://arstechnica.com/science/2026/03/leading-explanation-...