Liquid Nitrogen Isn’t Suitable For Steam Engines

Liquid nitrogen is fun stuff to play with, as long as you’re careful and avoid freezing your own fingers off and shattering them on the workbench. As the liquid turns to gaseous nitrogen at around -196 C, [The Action Lab] figured that it could be used to propel a simple steam engine at room temperature. Testing this out had amusing results.

The device under test is a Hero’s Engine, otherwise known as an aeolipile. This consists of a hollow sphere filled with water, fitted with a series of nozzles that shoot out steam when the vessel is heated. Via the rocket principle, this causes the device to rotate about its axis.

When filled with water and heated with a candle, the aeolipile spun at up to 2520 RPM. [The Action Lab] next tested it filled with water in a vacuum chamber, with the low pressure causing the water to boil at room temperature. The effect was less impressive however, with the engine spinning at a much slower rate.

The best result was with liquid nitrogen inside the engine. With the nitrogen quickly boiling at room temperature, the aeolipile quickly spun up to a great speed. The engine stand had to be steadied to avoid it tipping over, before the seal at the top of the engine blew off from overpressure.

We’d love to see the same experiment done with a piston-type steam engine, too. Video after the break.

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Historical Hackers: Hero Builds Vending Machines

We tend to think of mechanical contrivances as products of the industrial revolution and true automation as something computers handle. Yet even before computers, automation existed — using timing motors and cams and other mechanical contraptions. But it might surprise you to know that there was actually some sophisticated automation going way back. Really way back, invented in a world without computers, CAD software, or even electricity. For example, around 50 AD an inventor named Hero — sometimes known as Heron — built machines powered by steam and wind. His inventions included vending machines and music players.

It is hard to imagine what kind of music player or, indeed, vending machine you could build in 50AD. Some of Hero’s inventions were used in temples to, for example, dispense holy water. Others were used in theater to do things like automatically lighting a fire or creating thunder effects. There was even an entirely automated puppet show that used knotted ropes to put on a ten-minute production with no human assistance.

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The Simplest Steam Engine

[RimstarOrg] has posted an awesome writeup on his Hero’s steam engine . Hero’s engine is a Greek design from the first century and is the earliest known steam engine. It’s amazing to think he developed the engine seventeen centuries before the industrial revolution, and yet it was largely ignored. While you can find more faithful replicas, of this landmark machine [RimstarOrg]’s rig can’t be beaten for simplicity and he does a great job of explaining the principal of operation and construction.

Using a soda can filled with water and a propane torch [RimstarOrg] was able to get the can to rotate rapidly by ejecting steam from two holes in the side of the can. A fishing swivel is used to provide a pivoting joint and allow the can to rotate freely.

While we’ve covered steam engines before, we loved this simple design, and can’t wait to see what [RimStarOrg] comes up with next.

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