Stirlingengineforum.com

There is a playlist with, I think, about 7 additional videos:

https://m.youtube.com/playlist?list=PLa ... ZbZ15tE4uD

I'm still having a bit of trouble, though I understand your explanation of "the simplest 'motor' possible", I can't seem to find any examples or description, such as a demonstration video or how-to article.

All I've been able to find are examples of the attractive (or solenoid) type. My limited understanding is that the induced current is always "equal but opposite" making it attractive, even if the current is reversed.

Anyway, I would expect to see dozens of such simple video demonstrations of basic motor principle just using a current in a loop of wire to levitate an object, or another loop or ring Or whatever.

In other words, the magnetic flux around the first loop and the second loop cancel each other in relation with each other, preventing or inhibiting motion rather than inducing it, so that without a second (or rather third) loop or coil or magnet of some sort, no motion or levitation takes place.

Admittedly, my knowledge regarding such things is wanting and probably flawed, but I'm so far not able to find any evidence to prove myself wrong..

I have never seen anything like it too, I was basing my intuition on flux conservation and the overall magnetic energy decreasing with the coils separating, reduction in mutual inductance if you want. In terms of forces flux conservation means opposite currents and opposite currents repel.

I've been trying to gather more information on this for the past couple of days. There are plenty of sites, videos etc. like this:

https://youtu.be/lkwheWiVOiw

All however involve "current carrying wire". That is; wires with an active flow of current produced by an applied electrical potential, such as a battery or other electrical supply.

There seems to be a complete absense of any reference to what happens when the second wire is carrying an induced current, other than, as in an induction motor, an additional current carrying wire may repel and/or attract the wire or coil carying an induced current.

So, why is this never addressed or explained? I haven't been able to find anything on the subject.

My personal thought is that there is something about the nature of electromagnetism that disallows this scenario.

There is, presumably, something different about an induced secondary current, in relation to the primary, as opposed to two currents (or one traveling in two directions) resulting from an "outside" source of electrical potential.

To conceptualize this, I imagine something like a circular trough or gutter of water on a merry-go-round.

If I put a paddle in the trough extending from another merry-go-round wheel and turn the first wheel there will be a kind of "induced current" in the second. The induced current will be apparent to an "outside observer" but in relation to the first there will be no relative motion or difference. They will be moving together.

Take another scenario, I walk around the trough, pushing the water along with my hand. I'm inducing a current relative to a bystander, but the same current is stationary in relation to the inductor.

If I chain the merry-go-round down so it can't turn and push the water around, it will be moving in relation to someone on the merry-go-round and also an outside observer off the merry-go-round but motionless to me as I'm walking along with the water as I push it, but the merry-go-round itself will be moving from my own perspective, though chained to the ground.

If I take off the chain allowing the wheel to turn, then the "resistance" between the water and wheel and myself will have everything seemingly stationary, though everything is moving.

What I'm wondering is, what if a capacitor is introduced in the second wire?

Then, when I push the water, it flows into a kind of reservoir, then comes back. The induced current on the return trip, would then be independent of the current that induced it.

Maybe.

Or something along those lines, perhaps.

This is, of course, all wild theory and speculation, but might be something to experiment with.

It is a bit odd to me that this question is never mentioned or addressed in the dozens of sites and video demonstrations available that I've been looking at.

You can calculate the induced current by putting the shared flux to zero and then letting it decay according to its L/R time.
It's actually electromagnetism textbook stuff, the classic way of dealing with it analytically is by calculating energies through self and mutual inductances and then gradients to get forces. Believe me it would work if the time constant would be long enough and I have already checked that. You probably can't find it in examples because it's not an actual useful motor in other applications. It's such a simple geometry that one can compute it all in finite form, numerically, with a spreadsheet and you can find all formulas on line if you want but why don't you calculate your idea instead which I think it's more promising? I am not very motivated right now but I can help you if you want.
On the other side did you understand how is the displacer controlled in the free piston engine of the video?

"On the other side did you understand how is the displacer controlled in the free piston engine of the video?"

Of the many, many Stirling/heat engines I've seen over the years, this one always impressed me greatly The heat utilization being so efficient that no active cooling needed.

I can't say, though, that I've studied it in enough depth to understand the details of how it works exactly. I only just, with my last post about it here, became aware of some of the additional videos

My general impression though is that the displacer is not "controlled" exactly, but this is probably a free-displacer as well as free-piston of which I've seen a few the displacer and piston finding their own natural groove.

This simple LTD type for example:

https://youtu.be/kcbQGug8Obg

Sometimes there is not even any spring, but "air springs" of one sort or another. Or just "free piston" with no displacer at all.

There was one engine of sorts with no moving parts at all, just a tube with regenerator, being propelled along by 'thrust', though very weakly.

https://youtu.be/uZwQwztWC2A

"You probably can't find it in examples because it's not an actual useful motor in other applications"

Well, a couple wires dangling and repelling each other doesn't make a useful motor either, but examples and demonstrations abound. If current in just one wire could produce the same result, I'd think such a phenomenon would be notable and worth mentioning by at least one or another of these MIT professor types.

I don't want to sound overly argumentative or skeptical, but I'm not prone to waste too much time chasing after rainbows either. I don't always care WHY something works, so much as just observing that it does in fact work. So far, I've been unable to make such an observation that a current in one wire can repell a second wire by way of induced current, or back EMF or whatever.

If it is possible, it seems, it should be an extremely simple matter to demonstrate.

I may just do some such experiment myself, when I've got nothing else pressing to do, in the next few days, and put up the results on my YouTube channel. See if it works or not.

Edit: On the other hand, I did find this: I have my doubts as far as seeing any improvement in efficiency though.

https://youtu.be/Pp_nvYVVCyU

If you want to test the induced current repulsion scheme the simplest way would be to discharge a capacitor into a loop and see a second short circuited 1 turn loop jump up. I have never seen it in practice, it's a prediction.

"If you want to test the induced current repulsion scheme..."

That seems to me, a logical preliminary. I don't know, or have absolute confidence in mathematic assumptions, particularly when no one involved in such things seems to have taken any note of any such observation.

2+2 as an abstract mathematical concept does not always pan out when working with real quantities.

There is a local motor repair shop that has an entire isle in the store with shelves full of capacitors. Some guidance as far as what to ask for would be helpful as I know next to nothing about them.

Otherwise I do have a few old Briggs and Stratton point and condenser sets. They don't come with any specifications, but appear to be the same as what would be found for an automotive points set.
Actually, now that I look at it, this set is for a car or truck.

It needs to be safe, i.e. less than 100 V fully charged, and reasonable size, physical size is proportional to energy , my guess is that this would be ideal All cables at least like 1 mm diameter of total x-section, the cable from capacitor to L1 twisted, better if L1 is a few turns, L2 rigid wire, same loop size as L1, short circuited, number of turns doesn't matter.
Better if you use a switch but the contact shouldn't spark on closing, disconnect power supply when shorting, that's why a on-off-on spdt switch would be better.
I didn't calculate anything, I hope something moves but I'm not sure of course.

I just came across this:

https://youtu.be/S9DhMu-J3Ck

There is an instructables:

https://www.instructables.com/Levitating-Platform/

Now I'm wondering if it would be possible to levitate a regenerative displacer. Perhaps made of aluminum window screen.

That might allow reclamation of the probable heat generated, as well as allowing some air flow through, keeping the "platform" from getting too hot and melting.

Not quite an oscillating circuit there but I think this lends something to the feasibility of your proposition.

In a motor this kind of setup would not produce rotational torque without a starting circuit to get things turning.

Edit:

An interesting method to center the displacer without the guides.

https://youtu.be/azsqhKg8hX8

I assume this would also work in reverse, if the coil levitated an aluminum "disk" that was divided into four parts.

the principle is exactly the same, alu vs cu

There are a few things bothering me about all this.

I think we've conclusively established, with enough current lift of the displacer is possible.

Theoretically, I'm not certain that an oscillation in the circuit is possible. Let's say we have a capacitor discharge, the displacer lifts, the engine turns or moves and much, or at least some of that original charge in the capacitor is converted to mechanical "work" and/or lost as heat, if not immediately, over time.

It is not clear to me how the oscillation of current would be sustained, or the capacitor recharged for the next, and succeeding lifts.

I can see how in an oscillating circuit, where there is no significant mechanical work or output, the oscillation could continue for some time, like a spring suspending a weight, or pendulum swinging, but in the two previous videos, sustained AC power is applied and the "platform" or whatever is suspended, until the power is cut off. A tremendous amount of energy is dissipated as heat.

I have a vague idea that by somehow matching the frequency of the rise and fall of the displacer with the frequency of the oscillating circuit,... along with some means of nudging the oscillation, like someone occasionally giving a push to a friend on a swing at just the right time, my thoughts trail off.

A linear pulse motor?

A search on that term brings this up on YouTube:

https://youtu.be/EMpry_2-580

Looks very similar to a "thermoacoustic" or "laminar flow" or "thermal lag", variously called, type Stirling engine.

I don't immediately find any explanation of how this pulse motor works or how it is wired, but maybe worth looking into.

"It is not clear to me how the oscillation of current would be sustained, or the capacitor recharged for the next, and succeeding lifts."

The oscillator is only electrical, an underdamped RLC circuit. Part, or all, of the current flows also in the circuit which lifts the displacer and part, or all, of that same current flows in the coil set in motion by the piston or diaphragm. If the power dissipated in the conductors is less than the power the engine transfers to the circuit the system sustains its oscillations.
There is nothing else to it and it's not too difficult to compute in a spreadsheet with sufficient approximation. The result will be a minimum delta T at the engine for sustained oscillations. With superconductors it would certainly work, with real conductors it depends on resistance.
If you start setting up a spreadsheet I'll help you to fill the cells.
The model can be time dependent or averaged over the cycle, both would work but I think the time dependent option is physically clearer and more fun.
One should start by modeling the RLC circuit oscillations, which is so common you would find it already done in excel or ODS on the web, then we can introduce the other two components which are less obvious but still doable under reasonable assumptions.
If the analysis shows it works and easy to set up in practice the most fun would then be to compare the model with real oscilloscope, or arduino, traces.

In theory, and for the most part also in practice, a Stirling engine displacer takes next to nothing in terms of energy to move. The air resistance and/or friction would be, probably no more within an engine than outside, or independent of it.

What little energy it does require to move the displacer is usually parasitic.

If some device similar to the previous levitating "platform", or the "linear pulse engine" could be designed to run independently using some very low input source, such as a penlight (1.5v AA) battery, Then I should think it would work just as well in a Stirling engine.

With that the engine would just need to put out enough current to keep the battery topped off.

As far as controlling or trying to synchronize the displacer and piston for maximum power, perhaps that could come later.