Or, maybe it would be better to start with a Stirling engine with a magnetic piston running through a coil around the cylinder.
See what sort of current can be generated, probably unmodified AC.
Put that into an oscillating circuit that passes through the wire/coil to lift the displacer.
As far as any mathematics involved to figure out sizes of components, number of windings, frequencies or any of that, I'm at a loss I'd be left to trial and error.
Arduino looks interesting. Probably a good resource for someone who knows what they are doing and how to use it, but I'm pretty much lost there as well.
I'm still not sure I have any clear idea what it is you're proposing, but I assume, in practice, it would have to start with giving the engine some manual kick start of some sort. Something, I would suppose, a permanent magnet, moves past a coil to generate the initial voltage to activate the circuit.
I was thinking perhaps a variable capacitor might be useful for tuning the circuit to the engines natural frequency, or possibly as a speed control? Or just to play around with.
Does this sound anything like what you had in mind?
LTD magnetic vs gamma
Re: LTD magnetic vs gamma
BTW, I tried looking up ODS, not knowing what you were referring to
Operational data store,
Office of Dietary Supplements,
Official Document System,
Ozone-Depleting Substances,
The top results
An Online dictionary provides this list of acronyms for ODS:
https://acronyms.thefreedictionary.com/ODS
Missing from that seemingly exhaustive list is OpenDocument Spreadsheet, which being related to Excel, I decided, must be what you were referring to.
Wondering what a spreadsheet has to do with electronic circuits, after some additional poking around, I found skatered about some references, such as this:
APPLICATION NOTE 1947
EXACT CIRCUIT ANALYSIS WITH MICROSOFT EXCEL
By: Brian C. Wadell
https://www.maximintegrated.com/en/desi ... /1947.html
Needless to say, I have no clue of any sort what you are asking when you say: "If you start setting up a spreadsheet I'll help you to fill the cells."
"...you would find it already done in excel or ODS on the web,..."
As true as that may be, a link or two, if you have something might save some time. This is mostly all 100% new territory for me, and "the web" is a rather enormous haystack.
Some sort of video tutorial on using spreadsheets for this sort of thing would be helpful, I guess, but this is about all I can find, which is far too advanced, for me anyway.
https://youtu.be/aBbFLsy83eQ
Operational data store,
Office of Dietary Supplements,
Official Document System,
Ozone-Depleting Substances,
The top results
An Online dictionary provides this list of acronyms for ODS:
https://acronyms.thefreedictionary.com/ODS
Missing from that seemingly exhaustive list is OpenDocument Spreadsheet, which being related to Excel, I decided, must be what you were referring to.
Wondering what a spreadsheet has to do with electronic circuits, after some additional poking around, I found skatered about some references, such as this:
APPLICATION NOTE 1947
EXACT CIRCUIT ANALYSIS WITH MICROSOFT EXCEL
By: Brian C. Wadell
https://www.maximintegrated.com/en/desi ... /1947.html
Needless to say, I have no clue of any sort what you are asking when you say: "If you start setting up a spreadsheet I'll help you to fill the cells."
"...you would find it already done in excel or ODS on the web,..."
As true as that may be, a link or two, if you have something might save some time. This is mostly all 100% new territory for me, and "the web" is a rather enormous haystack.
Some sort of video tutorial on using spreadsheets for this sort of thing would be helpful, I guess, but this is about all I can find, which is far too advanced, for me anyway.
https://youtu.be/aBbFLsy83eQ
Re: LTD magnetic vs gamma
This video is interesting, and I think helpful:
https://youtu.be/4rUBrLvSDUY?t=670
About 11:00 into the video he talks about a simple circuit consisting of just an AC supply and an inductor and covers the fact that in such a circuit the current is 90° out of phase with the voltage.
Which he demonstrates on the scope at about 16:00
https://youtu.be/4rUBrLvSDUY?t=1004
A displacer is, by general convention, in an LTD Stirling, also 90° out of phase with the piston.
So, perhaps a direct line from the magnetic piston with a coil generating AC to the displacer "levitating platform" actuated by an inductor coil would do the trick.
https://youtu.be/4rUBrLvSDUY?t=670
About 11:00 into the video he talks about a simple circuit consisting of just an AC supply and an inductor and covers the fact that in such a circuit the current is 90° out of phase with the voltage.
Which he demonstrates on the scope at about 16:00
https://youtu.be/4rUBrLvSDUY?t=1004
A displacer is, by general convention, in an LTD Stirling, also 90° out of phase with the piston.
So, perhaps a direct line from the magnetic piston with a coil generating AC to the displacer "levitating platform" actuated by an inductor coil would do the trick.
Re: LTD magnetic vs gamma
Our collaboration is getting interesting from a totally unexpected point of view, your way of proceeding is teaching me the quirky logic and extraordinary power of the web in problem solving.
APPLICATION NOTE 1947
EXACT CIRCUIT ANALYSIS WITH MICROSOFT EXCEL would help to but I was thinking more at something like
http://www.engineers-excel.com/Apps/ODE ... iption.htm
which follows instant by instant the time evolution of current and voltage, it would allow to change parameters while they evolve, we need only one cycle and a spreadsheet is adequate.
Following https://en.wikipedia.org/wiki/RLC_circu ... from%20RLC.
the values to insert in the spreadsheet are f(x)=V(t)=0, a=R/L, b=1/LC, with initial conditions, y(0)=I=0 and y'(0)=1
Start from frequency f=10Hz, that is LC = (2 *3.14* 10)^2 and then try to understand which R, L, C are practically better values to adopt.
It sounds difficult but it's really necessary to proceed with an incremental understanding, next step we introduce the displacer with my scheme for example, to demonstrate that it's probably very hard to do it in practice, power-wise.
Hopefully I didn't err too much, check as much as possible of what I am saying.
APPLICATION NOTE 1947
EXACT CIRCUIT ANALYSIS WITH MICROSOFT EXCEL would help to but I was thinking more at something like
http://www.engineers-excel.com/Apps/ODE ... iption.htm
which follows instant by instant the time evolution of current and voltage, it would allow to change parameters while they evolve, we need only one cycle and a spreadsheet is adequate.
Following https://en.wikipedia.org/wiki/RLC_circu ... from%20RLC.
- Untitled2.png (8.72 KiB) Viewed 5422 times
Start from frequency f=10Hz, that is LC = (2 *3.14* 10)^2 and then try to understand which R, L, C are practically better values to adopt.
It sounds difficult but it's really necessary to proceed with an incremental understanding, next step we introduce the displacer with my scheme for example, to demonstrate that it's probably very hard to do it in practice, power-wise.
Hopefully I didn't err too much, check as much as possible of what I am saying.
Re: LTD magnetic vs gamma
There is a thread
viewtopic.php?t=711
that discusses the reason for the 90° phase angle in a Stirling engine with piston and displacer.
I think I was mostly wrong suggesting that the inductor would provide that.
The current in the inductor would be associated with the magnetic field controlling the movement of the displacer, which in a Stirling engine, would need to lead ahead in advance of the piston by 90°
In a circuit with only an AC supply and an inductor, the current lags behind the.voltage. the opposite of what is wanted.
A condenser would be opposite, providing current at the right time, but a condenser is not an inductor.
My guess is, what is needed is an LRC circuit where the condenser dominates to provide a current that leads voltage and the inductor is all but non existent, just enough of a loop of wire to produce a field sufficient to float the displacer but not alter the phase shift provided by the condenser.
Or, getting a bit wild
Perhaps a 4 cylinder Stirling engine could have circuits where cylinder #1 provides the lift for the displacer associated with the #4 cylinder and so forth.
Possibly the phase angle will change with RPM.
In general, the higher the RPM, the more the displacer movement should be in advance of the piston. Infact, at start, it might not be bad to have the piston slightly in advance of the displacer for easy starting.
I should also mention that IMO in an engine with a fast moving "free" displacer the "ideal" phase angle would be much less than 90° at normal operating speed.
Also, advance the engine enough, or reverse it, and you have the makings of a Stirling cryo-cooler.
Anyway, I picked up a roll of aluminium window screen last night to try out the 4 sectional levitating regenerative displacer concept.
Edit:
Or, come to think about it, I have something of an obsession with operating Stirling engines in reverse on ice.
In that case, I think the phase angle is reversed as well, for a little LTD engine
https://youtu.be/lFhUkzHRbWo
In that experiment the engine ran for 32 hours on a cup of ice, but I had a little problem getting enough ambient heat down into the engine. That's the reason for the big aluminum "heat sink", which in this case is working in reverse as a way to draw additional heat down to the engine
A displacer that acts as a kind of induction heater right inside the engine might be just the ticket.
viewtopic.php?t=711
that discusses the reason for the 90° phase angle in a Stirling engine with piston and displacer.
I think I was mostly wrong suggesting that the inductor would provide that.
The current in the inductor would be associated with the magnetic field controlling the movement of the displacer, which in a Stirling engine, would need to lead ahead in advance of the piston by 90°
In a circuit with only an AC supply and an inductor, the current lags behind the.voltage. the opposite of what is wanted.
A condenser would be opposite, providing current at the right time, but a condenser is not an inductor.
My guess is, what is needed is an LRC circuit where the condenser dominates to provide a current that leads voltage and the inductor is all but non existent, just enough of a loop of wire to produce a field sufficient to float the displacer but not alter the phase shift provided by the condenser.
Or, getting a bit wild
Perhaps a 4 cylinder Stirling engine could have circuits where cylinder #1 provides the lift for the displacer associated with the #4 cylinder and so forth.
Possibly the phase angle will change with RPM.
In general, the higher the RPM, the more the displacer movement should be in advance of the piston. Infact, at start, it might not be bad to have the piston slightly in advance of the displacer for easy starting.
I should also mention that IMO in an engine with a fast moving "free" displacer the "ideal" phase angle would be much less than 90° at normal operating speed.
Also, advance the engine enough, or reverse it, and you have the makings of a Stirling cryo-cooler.
Anyway, I picked up a roll of aluminium window screen last night to try out the 4 sectional levitating regenerative displacer concept.
Edit:
Or, come to think about it, I have something of an obsession with operating Stirling engines in reverse on ice.
In that case, I think the phase angle is reversed as well, for a little LTD engine
https://youtu.be/lFhUkzHRbWo
In that experiment the engine ran for 32 hours on a cup of ice, but I had a little problem getting enough ambient heat down into the engine. That's the reason for the big aluminum "heat sink", which in this case is working in reverse as a way to draw additional heat down to the engine
A displacer that acts as a kind of induction heater right inside the engine might be just the ticket.
Re: LTD magnetic vs gamma
yes volume expansion and displacer need to be roughly in quadrature, doesn't matter which way. In a standard engine the direction of rotation is automatically consistent with the sign of the phase difference, in the electrical case it boils down to the phase of the two current, the generator and the displacer magnet.
it's early to think about it though since it doesn't involve any dissipation, we'll always find an isentropic way to get the phase right.
Now what we need to understand is how to move the displacer efficiently and cheaply with a current.
it's early to think about it though since it doesn't involve any dissipation, we'll always find an isentropic way to get the phase right.
Now what we need to understand is how to move the displacer efficiently and cheaply with a current.
Re: LTD magnetic vs gamma
An additional potential problem that comes to mind is, in a "levitating platform" powered by an AC current, the changing magnetic field produces a repulsive force or "lift" regardless of the direction of current flow, or regardless of whether the magnetic field is increasing or decreasing. Or am I wrong?
So, if the piston acts as a linear AC source, producing current in one direction as it goes up, and the other as it goes down, the displacer may just continue to float rather than rising and falling. Or am I mistaken?
In the various "levitating platform" examples above, the platform continues to levitate as long as the AC current is applied.
So, if the piston acts as a linear AC source, producing current in one direction as it goes up, and the other as it goes down, the displacer may just continue to float rather than rising and falling. Or am I mistaken?
In the various "levitating platform" examples above, the platform continues to levitate as long as the AC current is applied.
Re: LTD magnetic vs gamma
you are right, just repulsive, if it's efficient we'll find a way to get it down again at every cycle. Gravity? Two circuit one at the top and one at the bottom for the two current polarities, with diodes? You suggested a sucking solenoid but one could use permanent magnets instead which give rise to reversible forces
Re: LTD magnetic vs gamma
I had been thinking that one circuit with two inductor coils in parallel(?) perhaps on either side of the displacer as you say, with diodes to divert the oscillating current through one coil or the other, as there should, I think, be two pulses from the piston for each cycle
It would seem the "problem" is certainly not insurmountable.
It would seem the "problem" is certainly not insurmountable.
Re: LTD magnetic vs gamma
I had to strain my brain a bit, but came up with this depiction of combined circuitry and mechanical aperatus
I made no real attempt to depict any exact arrangement or positioning of the components. The displacer might better be suspended vertically, the piston parallel to the displacer rather than horizontal etc. Many different configurations are possible.
I used a heat lamp to depict a heat source, mostly to avoid difficulties, such as having a candle flame burning up the insulation on the coils or some such.
The upper side of the displacer is darkened to help absorb light, could be solar powered.
The piston, on the right, is, of course, magnetic, and generates an AC current in the circuit as it reciprocates through the windings surrounding the cylinder.
The rest of the circuitry is simple and should need no explanation: capacitor, diodes, inductor coils to direct an alternating magnetic field to move the displacer back and forth, which, of course, results in alternating heating and cooling - expansion and contraction of air in the displacer chamber that results in the magnetic piston moving through the coil to generate the AC.
Edit:
On second thought, that probably won't work. For the same reason as before. Though the current is "alternating", it is still passing through both coils, which are pushing against the displacer simultaneously from opposite sides. They cancel each other out.
Edit: or would it?
On second second (or third) thought, maybe it would work.
I made no real attempt to depict any exact arrangement or positioning of the components. The displacer might better be suspended vertically, the piston parallel to the displacer rather than horizontal etc. Many different configurations are possible.
I used a heat lamp to depict a heat source, mostly to avoid difficulties, such as having a candle flame burning up the insulation on the coils or some such.
The upper side of the displacer is darkened to help absorb light, could be solar powered.
The piston, on the right, is, of course, magnetic, and generates an AC current in the circuit as it reciprocates through the windings surrounding the cylinder.
The rest of the circuitry is simple and should need no explanation: capacitor, diodes, inductor coils to direct an alternating magnetic field to move the displacer back and forth, which, of course, results in alternating heating and cooling - expansion and contraction of air in the displacer chamber that results in the magnetic piston moving through the coil to generate the AC.
- IMG_20210418_074027802.jpg (121.87 KiB) Viewed 5358 times
On second thought, that probably won't work. For the same reason as before. Though the current is "alternating", it is still passing through both coils, which are pushing against the displacer simultaneously from opposite sides. They cancel each other out.
Edit: or would it?
On second second (or third) thought, maybe it would work.
Re: LTD magnetic vs gamma
My reasoning as to why it might work is this. (Not concerning myself with exact timing or which side is being heated or other details like number of turns on coils etc.)
The piston goes, say, to the right. The diodes cause the current to flow counter-clockwise in the upper loop. But the charge on both legs of the upper loop are equal and opposite. Also the inductor has back EMF, a kind of "resistance" that delays flow, as a result of the oppositional forces, current flows into the capacitor instead, charging the capacitor.
About the same time the other side of the capacitor is discharging through the lower induction coil, pushing the displacer up, which moves air in the chamber down -cooling the air, causing it to contract, drawing the piston in, which repeats the whole process on the opposite sides.
Likely this could all be taking place at a rather high frequency, and the delay caused by the back EMF in the inductors may only be on the order of milliseconds, but as the magnetic piston is controlling, the oscillations should keep in step.
I'm a bit concerned that if this actually worked, as more HEAT is added, with virtually nowhere to go, other than to add more voltage to the circuit, since little would be lost, in theory, anyway, some load should be in the circuit that could be switched on.
There could, in theory, also, be some voltage spikes ("Flyback") that could fry the diodes, so maybe some resistors across the inductors. That last is not my idea and I don't really understand the mechanism involved, how a resistor prevents this exactly, but I'm basing the possible need for some resistors on this video:
https://youtu.be/d-E12DlzGGc
But then I'm also wondering if such a sudden discharge of energy in the circuit is not exactly what we want. At the right time, it might allow use of a much smaller initial current to be generated by the piston that builds up, then discharges suddenly to kick the displacer to the opposite side.
Actually, he says diode not resistor. So... Flyback is in the opposite direction of the current? Maybe it wouldn't be a problem, or maybe more of a problem than I thought. I'm obviously no expert on circuits, but this seems like a beginning anyway.
The piston goes, say, to the right. The diodes cause the current to flow counter-clockwise in the upper loop. But the charge on both legs of the upper loop are equal and opposite. Also the inductor has back EMF, a kind of "resistance" that delays flow, as a result of the oppositional forces, current flows into the capacitor instead, charging the capacitor.
About the same time the other side of the capacitor is discharging through the lower induction coil, pushing the displacer up, which moves air in the chamber down -cooling the air, causing it to contract, drawing the piston in, which repeats the whole process on the opposite sides.
Likely this could all be taking place at a rather high frequency, and the delay caused by the back EMF in the inductors may only be on the order of milliseconds, but as the magnetic piston is controlling, the oscillations should keep in step.
I'm a bit concerned that if this actually worked, as more HEAT is added, with virtually nowhere to go, other than to add more voltage to the circuit, since little would be lost, in theory, anyway, some load should be in the circuit that could be switched on.
There could, in theory, also, be some voltage spikes ("Flyback") that could fry the diodes, so maybe some resistors across the inductors. That last is not my idea and I don't really understand the mechanism involved, how a resistor prevents this exactly, but I'm basing the possible need for some resistors on this video:
https://youtu.be/d-E12DlzGGc
But then I'm also wondering if such a sudden discharge of energy in the circuit is not exactly what we want. At the right time, it might allow use of a much smaller initial current to be generated by the piston that builds up, then discharges suddenly to kick the displacer to the opposite side.
Actually, he says diode not resistor. So... Flyback is in the opposite direction of the current? Maybe it wouldn't be a problem, or maybe more of a problem than I thought. I'm obviously no expert on circuits, but this seems like a beginning anyway.
Re: LTD magnetic vs gamma
I'm thinking of picking up one or more of those shake-up rechargeable flashlights. They already have a simple linear alternator, coil, magnet, circuitry, housing etc, and demonstrably can be operated by a small homemade Stirling engine, and see if the output is anywhere near enough to budge a bit of aluminum foil or anything at all.
https://youtu.be/f9Cs3daKT6o
One problem is: the quality and price of the half dozen or so available shake up flashlights varies considerably. And price is not necessarily an indicator for these purposes, as being completely waterproof to 200 feet is of no concern here, it might just make it harder to take apart.
Or, I may just send away for some spools of magnet wire and magnets and such, but, as the flashlights are already sized as far as magnet, coil and other components to at least work together, it might make things a little easier.
Or not?
https://youtu.be/17RGJGtUdRM
In general, reviews suggest none of these shake flashlights are worth the money, even the "best".
https://youtu.be/4y76fwLeRIE
Nevertheless, I don't know of any particularly better way to proceed. Any additional guidance or advice would be welcome. I'm also just curious.
My son came around with one of these he gave me, that I used camping for years and years and it worked quite well, I thought, but don't remember what, if any brand it may have been.
https://youtu.be/f9Cs3daKT6o
One problem is: the quality and price of the half dozen or so available shake up flashlights varies considerably. And price is not necessarily an indicator for these purposes, as being completely waterproof to 200 feet is of no concern here, it might just make it harder to take apart.
Or, I may just send away for some spools of magnet wire and magnets and such, but, as the flashlights are already sized as far as magnet, coil and other components to at least work together, it might make things a little easier.
Or not?
https://youtu.be/17RGJGtUdRM
In general, reviews suggest none of these shake flashlights are worth the money, even the "best".
https://youtu.be/4y76fwLeRIE
Nevertheless, I don't know of any particularly better way to proceed. Any additional guidance or advice would be welcome. I'm also just curious.
My son came around with one of these he gave me, that I used camping for years and years and it worked quite well, I thought, but don't remember what, if any brand it may have been.
Re: LTD magnetic vs gamma
This is not, as far as I can tell, an example of inductive repulsion, but the text of the video does say that the coil is used to repel the magnet on the pendulum (rather than attract it).
Anyway, it also states that the pendulum will continue swinging for three months on two AA batteries.
IMO, a well balanced, suspended, pendulum type displacer should take little more power, which could likely be supplied by even the smallest Stirling engine.
While waiting for the flashlights to arrive, I've been conducting searches for "inductive repulsion pendulum" and similar terms, trying to find something similar to this but using inductive levitation type force. This is as near to that as I've found so far.
https://youtu.be/5tFGIQrKgBc
Anyway, it also states that the pendulum will continue swinging for three months on two AA batteries.
IMO, a well balanced, suspended, pendulum type displacer should take little more power, which could likely be supplied by even the smallest Stirling engine.
While waiting for the flashlights to arrive, I've been conducting searches for "inductive repulsion pendulum" and similar terms, trying to find something similar to this but using inductive levitation type force. This is as near to that as I've found so far.
https://youtu.be/5tFGIQrKgBc
Re: LTD magnetic vs gamma
what I proposed on day one is to measure the power to operate the displacer, quite separately from setting up the whole engine, precisely because that's the key to size everything else and the bit which is difficult to compute
Re: LTD magnetic vs gamma
The size of a displacer is proportional to the engine it goes in. It could be virtually any size whatsoever. Different types of engines require different types and weights etc. of displacer.
In my way of thinking to say "the" displacer is like saying THE tire.
Are we talking a tire for a tricycle, a wheelbarrow, or a tractor trailer truck.
I'm not at all familiar with spreadsheets or the math to be able to compute anything one way or the other.
I know a bit about generators, coils and magnets, so given a coil and magnet and a detectable output, whatever it's able to move, if anything, that thing, whatever it is, can serve as well as anything else as a displacer.
A formula, such as you posted earlier:
- Untitled2.png (8.72 KiB) Viewed 5325 times
I have a few small LTD engines with displacers I could take out and weigh and measure if that would help, but I have my doubts about such an engine being able to overcome the back EMF of any kind of generator powerful enough to lift a displacer, there are likely too many loses in power conversion from mechanical to electrical to magnetic, back to electrical back to magnetic back to mechanical.
I think for any chance for something to work it would likely necessitate a complete redesign of a customized engine to minimize the power necessary to move the displacer.
A pendulum type displacer IMO, is probably what would require minimal power, but such engines are fairly uncommon. I don't know of any for sale anywhere, but it is perhaps one of the easiest engines to build. But again, the displacer could be virtually any size. For me it is easier to just take a coil, put a magnet through it and see how big a sheet of aluminum or whatever it can move. That will be the displacer.
To me it makes sense to find something that works, that I can see working, and build the engine around that.
Then if somebody wants to scale that up, some calculations would no doubt come in handy.
I don't mean to be argumentative or anything, but as much as I might like to, I don't know when I'd have the time to download and figure out some spreadsheet program or other, but I do already have a workbench and a hacksaw and soldering gun and such.