Ethanol-Powered Arduinos

Following the time-honored YouTube tradition of ordering cheap stuff online and playing with it while the camera runs, [Monta Elkins] bought a Stirling engine that drives a DC motor used as a generator. How much electrical juice can this thing provide, running on just denatured alcohol? (Will it blend?)

The answer is probably not really a spoiler: it generates enough to run “Blink.ino” on a stock Arduino, at least when powered directly through the 5 V rail. [Monta] recorded an open-circuit voltage of around 5 V, and a short-circuit current of around 100 mA at a measured few hundred millivolts. While he didn’t log enough of the points in-between to make a real power curve, we’re guessing the generator might be a better match for 3.3 V electronics. The real question is whether or not it can handle the peaky demands of an ESP8266. Serious questions, indeed!

The video is a tad long, but it’s more than made up for by the sight of an open flame vibro-botting itself across his desk while [Monta] is trying to cool the cold side down with a melting ice cube. Which got us thinking, naturally. If you just had two of the Stirling enginesContinue reading “Ethanol-Powered Arduinos”

Easy Free Piston Stirling Engine

Stirling engines are really cool machines, invented by Reverend Dr. Robert Stirling in 1816 to rival the steam engine, they are one of the most efficient engines ever conceived.  Building one is a very rewarding experience, but it has a certain level of difficulty. However, [Attila Blade]’s version of a free-piston type Stirling engine is simple enough to be built in a matter of minutes.

To build the engine you only need a test tube, steel wool, a latex glove, an O ring and some wire. The construction is straightforward as you can see in the video. The whole engine rocks on the wire frame which also makes it different to most other Stirling engines that you can watch on the net. The free piston is just one type of several possible configurations for a Stirling. The most common one, is the beta type, usually made with soda cans, but it is much more difficult to build than [Attila Blade]’s engine.

This is definitely a fun project that you may want to try, and is also a great way to learn  thermodynamics concepts. Even if you don’t build this particular version, there are many other possibilities using mainly household items, or you can also check the very interesting history behind the Stirling engine.


Thermoacoustic Engine has Only One Moving Part

Modern internal combustion engines have around 500 parts, with many of them moving in concert with the piston. But have you seen an engine with only one moving part, out of four in total? In the thermoacoustic engine, the power piston is the only part in motion. [YTEngineer] has built a very simple prototype that works on power provided by a tealight.

His little engine, slightly larger than a cigarette lighter, is composed of a test tube that serves as the cylinder, a smaller tube, called the choke, that fits inside the test tube, the stack, which is nothing more than some steel wool, and the power piston. [YTEnginer] nicely explains how the engine works: basically a temperature difference is used to induce high-amplitude sound waves that create the piston’s back-and-forth movement. The engine can be easily converted to an electricity generator by adding a magnet to the piston and a coil surrounding it.

The thermoacoustic engine is a particular type of Stirling engine. They have been proposed as electricity generators for space travel using radioisotopes as the heat source, among other applications. You may be interested in the history of Stirling engines, or perhaps even build a simple one.

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200 Years of The Stirling Engine

In the early years of the nineteenth century, steam engines were at work in a variety of practical uses. However, they were still imperfect in many ways. One particular problem were the boilers, that had a tendency to explode, causing injuries and fatalities. Reverend Dr. Robert Stirling, a Scottish clergyman, was concerned about the death toll from exploding boilers. Based on previous work by George Cayley (known for his pioneering work on aeronautics), Stirling filed his patent for a safer engine in 1816. That makes this year the bicentenary of this engine. The Stirling engine has the highest theoretical efficiency of any thermal engine. It is also a relatively simple machine. Unlike other types of engines, there are no valves, and that makes the mechanical design much simpler.

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2-Stroke Engine too Beautiful to Behold

The sheer beauty of this build is blinding. We enjoy keeping a minimalistic household — not quite on the level of [Joe MacMillan] but getting there — yet this would be the thing we choose as decoration. It’s a hand-built 2-stroke Engine designed specifically to make the combustion process visible rather than locking it away inside of a block of metal.

If you have a nagging feeling you’ve seen this before it’s because the amazing craftsmanship is unforgettable. A couple years back we looked at the 4-stroke engine also built by [Huib Visser]. This new offering does away with the belt, leaving a build that is almost entirely glass and metal polished to a high sheen. The glass cylinder contains the combustion, pushing the graphite piston to drive the fly-wheel. A passing magnet triggers the spark plug to ignite the white-gas fuel, all of which is well-illustrated in the video after the break.

This is not for sale, which doesn’t surprise us. How hard would it be to part with something of such beauty especially knowing you created that beauty? But don’t worry, you can definitely build your own. Just make sure to set the bar lower for your first half dozen tries. We’ve even seen engine builds using hardware store parts.

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Sterling Engine Kludged Together From Whatever

Watching [Jam BD] build this working Sterling Engine from nothing is awe-inspiring. He literally did with what he had on hand. Even his build log forgoes phrases like “I ordered a…” in exchange for “I didn’t have any so…”.

The cylinder heated by a candle is a pipe stuffed with aluminum foil which was hammered flat to get the best seal possible. The CDs prominently featured on the final product act as the fly-wheel. To ensure that there is enough mass [Jam] ganged three of them together. There is also a counter-weight affixed just off-center to help keep the wheel turning. The gears shown above were actually used more like mounting plates to build a cam. Looking at the body and frame of the device makes us wonder how in the heck this thing actually came together?

We can’t get enough of these kinds of hacks, which is why we had to go back and watch the tuna can Sterling Engine one more time.

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Four-stroke engine with glass cylinder is a 2400 RPM piece of art

We know a lot about toggling bits in a register, but only a bit about how engines work. This one inspires us to throw ourselves into the field with reckless abandon. [Huib Visser] built this glass cylinder four-stroke engine and he took great care to make it beautiful. We don’t need our projects to be polished and gleaming, but we have to admit that this the opposite of what we see when popping the hood on our 12-year-old rust bucket out front.

You can’t see it in this image, but just on the other side of the fly-wheel is a smaller wheel with a cord wrapped around it that acts as the pull start. This gets the toothed timing belt going along with the cylinder. As part of the demo video we get a good look at how the rotary intake and exhaust valves work. [Huib] also took the time to demonstrate how the rare earth magnets and hall effect sensor reed switch synchronize the ignition system.

You won’t want to miss the end of the video which show it in action as It burns Coleman fuel (white gas) and is lubricated with WD-40. This is jaw dropping and it works like a charm, but still not that far removed from the concepts seen in [Lou’s] hardware store engine project.

UPDATE: Here’s write up this engine (translated) [Thanks ChalkBored]

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