What's the cost to build what you have there

That is impressive! How much output does stirling produce?

I have to disagree that it’s the first radical development in 200 years. I have been building engines with rotary displacers for years. And this was not my idea, the rotary displacer has been around for a long time.

I know this is silly but as an artist I am trying to make a robot design and this video was rather helpful, thank you for posting!

Very good idea. Are there any problems with taking it out of the water?

I'm doing a scaled up version of this right now.

When you mentioned the displacer spring having a resonance where the piston didn't and how that increased efficiency I pictured in my mind a displacer piston with springs mounted between the connecting rod and wristpin that might allow a second resonance to help transition the piston between cycles.

I think this is a truly novel design and shows real lateral thinking. Very well presented

What a fascinating new approach to the design of the displacer. I look forward to seeing it's further development.

In your animation the back of the piston is open to the atmosphere. You could use a double ended piston, and use two :engines' (running out of phase). This would also mean it would be easy to increase the pressure of the working gas. For solar (your application I believe) they could be side-by-side. Or the arrangement could be 'folded' to be either side of a rocket stove....

🥱🥱🥱🥱🥱🥱👎👎

That's an amazing engine to get that speed from boat!

Interesting to hear how little energy was required to keep the displacer at resonant frequency.

Hello Mr. Hall have you tried putting a small marble sized amount of steel wool in the hot syringe? Also, try wrapping some electrical copper wire around the regenerator. I have crushed pencil lead and rubbed it all over the piston which was a great idea. Lovely engine sir!

It's impossible to make it easier, it's a good option!

You can even make it simpler yet. - A flywheel is not needed - The working piston does not have to be solid, you can use a flexible membrane so the working fluid itself becomes the piston exerting pressure against the membrane which acts as a seal and spring. - The displacer piston does not have to be solid, you can use the same membrane idea as in the working piston. Alternatively you can use a solid displacer but replace the linkages by a membrane. So you can end up with a simple can of Stirling engine with 2 flexible membranes as the only moving parts. But you can still even go further and make a "Thermoacoustinc" engine, which means there is no displacer but a "stack" instead which is entirely immobile. So the only single moving component is a flexible membrane. And the best part is, since you have eliminated all the linkages you also eliminated all the fristion besides the inner friction of the working fluid itself. You also have less parts to machine AND the efficiency of such engines is still pretty good at about 30% and even more if you put in proper materials and engineering. This is incredible. I have also seen the so called "rice" engines, which are more or less a combination of a stiling and a steam engine. The working fluid works basically like in a stirling engine but the working fluid is replaced by steam, this creates an overpressure which needs releasing before first use while the engine is heating up. In turn the overpressure creates an even bigger vacuum inside when the steam cools off and phase changes to water again. This design is probably the most simple design, (besides the pressure regulation, which has to be done manually) it basically increases the "suction" stroke even more.

Very cool

Very nice 👍. I'm trying to workout what difference the unusual motion would make. It reminded me of one of Robert Stirling's parents, where he had a bell crank pivoting on the other moving arm.

This solution seems to be beneficial. I'd like to try them out sometime

Beautiful design and idea! So quiet. 🤩 If the cross sections of the spring from the side profile were aerodynamic (streamlined shape) and fit into similarly shaped grooves, the energy transfer per cycle would be less dissipative.

It’s so quiet. 🤩

Thx.

ok, your little engine engine is sitting there waiting, it is at stp, you start heating it, it runs, by what mechanism does the working fluid fall below atmospheric pressure when it is above ambient temperature? none of these demos are relevant, as pointed out by others here, ther's enough mass on the crank to do the job of a flywheel

i have found that you can also use the air bellow from a truck as a displacer. Works pretty well.

I question the regeneration capacity of the displacer, as in how much energy can be stored in the springs. Although, between the top and bottom springs, one could add steel wool. Iron has a density of 7.874 g/cm³ and can absorbe a great deal of heat energy per per degree of Celsius rise per cubic cm of material. The specific heat of iron is 0.451 J/g °C. That is higher than most materials one would use for a stirling regenerator. Iron in the form of steel wool has a high surface area to quickly absorbe that heat while letting the air pass through it. Thus the displacer may double in function as an efficent stirling regenerator.

I see a lot of sirtling engines with that kind of spring inside!

A normal displacer also stores energy in the flywheel so convinced by his logic there. Also where would the regen go ?

It seems to me that there is little working air. This limits its heat capacity. I wouldn't expect much power, but the efficiency may be high

I am sorry but this is a flexure spring and is far from new. Only took 5 minutes of Google searching.

If the spring had a near sealing quality when in its neutral state. The hot air would expand to initiate movement of the spring as if it were a piston. And the cold side would do the same with contraction. It seems as if a single spring could act as piston and displacer to simplify the unit. The center of the spring should support a rod extended below with a permanent magnet oscillating within a coil on the cold side as a linear generator.

You would have to match the frequency of the piston with the frequency of the displacer

Seems as though if you had to partition this concept, you'd simply end up with the basic cylinder concept as we know. What's the benefit to the spiral? And if it's the flexing; why not just use air pockets for oscillation?

Im a little confused, how does it begin to oscillate and how does it continue to oscillate? Is it just pressure differencial that makes it "tick" or is there an initial external force required to start or sustain the oscillation? Interresting idea for sure, glad that you shared it, is the engine a linear piston engine? So there is not even a flywheel?! Edit: Okay you drive it electro mechanically I assume, like a speaker?

Making a minor point. The air doesnt have to move around a displacer. Depending on the displacer design, It could in fact also move through the displacer.

That is so obvious that it makes me wonder why it wasn't done long ago!

run it between 8 and 9 Hertz and test the numbers - you'll get back to me ...

I've been studying wood burning stoves lately and i just happened to come across your video. It seems like you invented a brilliant way to maximize heat transfer in the high frequency/low flow conditions of a sterling engine. The springyness/resonance of the displacer seems like a bonus! How difficult is it to machine a piece like that?

Putting in a displacer with a cold side spring seems better because the engine can be thicker and the spring isn't subject to heat stress.

It is not entirely clear what drives the coil spring displacer. Or it works similarly as a membrane phase-shifting themoacoustic engine? If it's that thin the engine, then in theory the heat will pass through at a higher temperature without work, but of course the test of the pudding is eating... But I like this very much! I congratulations! I think, you could try to change the power piston for a longer and thinner tube and use turbine generator on it. Check the Metronome Heat Engine!

Just wanted to send some good luck to you all. Can't wait to see it pressured to 1000 psi using hydrogen or helium!

This is a really interesting idea. I will read more about it because I have a similar idea, but with no spiral springs in. Congratulation! BLADE

Wow very interesting. Instead of the springs pushing the displacer, the springs are the displacer.😀

The problem with all sterling engines, as with any engine or motor for that matter (including electric) is saturation. Stirling engines can be constructed to function on very low temperature differentials, and with comparatively crude materials/means. That's about where there merit begins and ends. I'm glad to see people keeping them alive, regardless.

Where did you get these engines?

Iron will heat faster as has higher electrical resistance and lower thermal conductivity Copper loses heat to air faster than iron. Heat lost to air is heat not directed where needed

It seems that they all will go faster if you apply more heat or increase the temperature difference by applying cold to the cold side with a water bath, or ice. Wrap the cooling fins with a wet paper towel and keep it wet and watch it go into a 3 speed or shift to second speed sooner on less heat. Cooling water or ice water on the cooling fins will mean less heat needed to go faster, thereby less chance of seizure of the expanding Piston. Or a high temp ( automotive) plastic/rubber hose, wrapped around the cooling fins in a coil pumping cold water around the cooling fins.

Awesome, love it. This is exactly what I had in mind the stirling engine is very efficient while the electric motor is also very efficient but very powerful as well. Range extender stirling engine, awesome. And how quiet the boat is.

Hey, can you please help me with my engine? I have tried mutiple times making my own design, which I have learned alot from, but I have never figured out why it never actually ran. You seem like you know a lot about stiring engines, so any help would be appreciated. Thank you.

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Hey Andrew, did you build it ?