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With the knowledge and tools required, could an atmospheric pressure engine train be built in the 15th-16th century? If so how effective would it be and what change would it bring to the world in that timeline?enter image description here

Also if these can't work efficiently, are there other possible alternatives?

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    $\begingroup$ Hi Eric, any chance you could give us a clue what an atmospheric pressure train is without having to look it up ourselves? $\endgroup$ – 011358 smell Apr 9 at 12:06
  • $\begingroup$ I presume you're talking about an engine like a "flame licker" or similar atmospheric engine (engine intakes hot air, the cooling produces a vacuum, atmosphere on the other side of the piston pushes it)... $\endgroup$ – Zeiss Ikon Apr 9 at 12:11
  • $\begingroup$ Or do you mean a pneumatic train, such as were experimented with in the late 19th century? $\endgroup$ – Klaus Æ. Mogensen Apr 9 at 12:15
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    $\begingroup$ What's an "atmospheric pressure engine"? Something like Newcomen's atmospheric steam engine? If so, no, that engine is useful only to pump water out of a coal mine; its efficiency is so low that it literally needs to have a coal mine right beside it. $\endgroup$ – AlexP Apr 9 at 13:00
  • $\begingroup$ It couldn't be done in the 19thC, no way could it be done 400 years earlier. $\endgroup$ – Separatrix Apr 9 at 15:02
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Generally, atmospheric engines have a very low specific power production -- enough so that I doubt you could build a practical train with one even with 20th century manufacturing technology.

If you look up YouTube videos of "flame licker" engines (one of the most common types of atmospheric engine), you see them running happily at good speed -- but I don't recall ever seeing such a video of the engine doing "useful" work, like turning an electric generator or pulling a load. From comments, atmospheric engines (described as "internal combustion", so not exactly like a modern "flame licker") were patented in the early 19th century and used for commercial (stationary) power (running pumps, mainly) in the middle of the 19th century, but over time they were beaten out by steam, which has a much higher specific power and can be made lighter for a given power level.

The underlying problem is that with a maximum of one atmosphere (in practice, a bit less) of pressure differential driving the piston, you have a tiny fraction of the power available that you'd get with either a combustion engine (which typically compress to several atmospheres before igniting the fuel/air mix) or an expansion engine (compressed air or steam engine -- again, typically operating on several atmospheres of supply pressure).

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    $\begingroup$ Samuel Brown patented the first internal combustion engine to be applied industrially, the gas vacuum engine. The design used atmospheric pressure, and was demonstrated in a carriage and a boat, and in 1830 commercially to pump water to the upper level of the Croydon Canal. ... The gas vacuum engine was eventually to become a commercial success. $\endgroup$ – Vashu May 8 at 5:19
  • $\begingroup$ @Vashu Thanks, I'd been aware the flame-licker, vacuum engine, or atmospheric engine that's a favorite of advanced model engine builders had a history in the real world, but wasn't aware it had been a successful design. I'll edit the answer accordingly. $\endgroup$ – Zeiss Ikon May 8 at 11:14
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The picture is from an atmospheric train, so I'll assume you mean that instead of "atmospheric engine". This is doubly good because Zeiss Ikon already answered that alternative.

Yes, it could be built, the technology and materials needed were available to Hero of Alexandria centuries before. He probably could have made one if somebody had paid for it.

It would be quite ineffective. The idea in the 19th century was to use steam engines which were not available in your time frame. You could use wind or water power instead but that has serious restrictions that reduce value. Air pumps would also have been less efficient due to less precise manufacturing.

More importantly before industrialization the resources needed to build and maintain the railway would have been extremely costly and there would have been no demand for large scale transport to pay for that. You need industrialization first, railways second.

Temporary railway to transport material for a specific large scale project might work. Or a short vanity project. Think building Taj Mahal or the Pyramids, or giving the guest to Royal Palace really cool way to arrive. But usually in such cases human labor would be the easier solution. But with specific circumstances... Why not. Hero did build pneumatically opened temple doors. A king might want "a house moving on tracks" and be able to afford it.

Another option that might be available is a short railway inside an industrial complex. If you are planning to build up local technology in some way concentrating your manufacturing projects into one location makes sense. You might have wind or water mills then use pneumatics or hydraulics they produce to power machinery. And if you use pneumatics you can also build an atmospheric railway inside the complex and it might be worth it since you'd already have the materials and trained personnel right there and the complex would actually have a need to constantly transport stuff.

What was generally used was canals. Building canals is highly labor intensive but the materials and maintenance are in general affordable. This matches pre-industrial economics much better

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