Hopefully attached is an image of a sketch of the magnet piston arrangement I was referring to as 'Case 3' in this thread:
http://www.overunity.com/8429/mostly-permanent-magnet-motor-with-minimal-input-power/105/
So it's a view thru the coil & core - as if cut in half... The plain steel armature is attracted when the coil is powered up, the one wrapped with the shorted coil is repelled. The fixed core provides a strong, static B-field for the armatures to act on. Ideally the throw isn't too long - 30-60mm depending on area is probably right.
The 'bias' permanent magnets are optional, and provide better response at low power, and make it all a bit more efficient.
The coil just has to saturate the 3 bits of steel - and it can do that with surprisingly little input power. Please see the thread I'm about to start on "Magnetic Field Equations Predict Overunity"... ;-)
The force you get between 2 magnets is proportional to the area of the facing sides * Bfield^2 / 2 * u0. So core face area matters a lot! You can also put big flat washers between the PMs & The steel on the shaft - to provide surface area on the outside of the coil too. This is often done with solenoids.
Anyway - according to my calcs this will make about 15 Horsepower at 1000rpm for a core diameter of 100mm and a throw of 40mm.
Electrical power required to saturate the iron cores? Perhaps 1000 amp-turns at most. Which we could provide with (far less than) 50 watts of input power...
Happy to go thru the calcs with folk...
Like this one in the video link
http://www.youtube.com/watch?v=tM_HRwqKzFk
Hi tinman. No it's not working on the same principles as the Gap-Power device. The only similarity is that they're both reciprocating engines.
Hi Tim,
thank you for taking the time to post this interesting variation of my design.
Would you not be able to also take advantage of the coils outside field like I demonstrated in my new video?
Are you able to build a prototype?... I could consider building a smaller version of it if that can help.
This is the kind of sharing I've been hoping for. It's been years since I started my Mostly Magnet Motor topic and you're the first to share a variation that could improve on what I have found.
Thanks for sharing
Luc
Hi Luc, yes you would be able to make use of the exterior field too. Both ends of the piston could have an exterior part too - like a washer, although if the coil itself was wrapped in steel the exterior flux would be negligible apart from right at the opening.
I've been working on the basis that the flux in the core of a solenoid is more or less constant throughout it's length - making the calcs easier. It's also by far the strongest flux. So if I can make it work just within the core - then that's at least a good start.
I think it was Wesley Gary who originally came up with the basic idea of using a coil & 2 opposing magnets - back in the 1800s. I saw your latest vid, and I was impressed. I think your design as it stands is a viable OU device - given scaling up and proper engineering.
I'm currently trying to turn my tumbledown barn into a decent workshop. Should be done next month. At which point I'll be getting it together to make prototypes, hopefully. According to my calcs, it would need a core diameter of min 60mm, and a length of 100-200mm to give OU, so a small prototype would probably be a waste of materials.
I'll send you a link to my coil calculator in a PM if you like... Not sure it's ready for the whole world yet ;-)
Here's a rotary version of the same thing, although I think the attraction is reversed due to the change in orientation of the magnets to one another...
The principle is that when the coil is powered, the iron parts of the rotor are repelled by the iron stator strips, while the shorted-coil section is attracted. Again it's a 50% duty engine (2 stroke).
The shorted-coil sections only produce an opposing field when the external magnetic field is changing, so the optimum motor speed will depend on the inductance of the main coil.
The main features:
- single external coil can be a big as you like.
- no brushes & not very difficult to build.
- strong, (but lumpy) power delivery (would need a flywheel). Large common surface-area between rotor & stator, and wide radius gives lots of torque.
Note that Maxwell said the maximum force between 2 ferromagnets is 100 tonnes per square meter. If the rotor surface area is 1m^2 then that's the maximum force it will be producing. It's a lot.
Reminds me of Bob Teal and his "magnipulsion motor":
http://www.free-energy.ws/bob-teal.html
http://www.rexresearch.com/teal/teal.htm
Greetings, Conrad
Hi Conrad :), yeah, quite similar indeed... Magnapulsion sounds a bit better than MagPis too... ;D
I wanted to try to give you guys something a bit more solid to work with, so...
Here are the calclulated specs for a buildable, fairly small version of this device (reciprocating version). I'd strongly suggest you do your own calculations before spending time and money trying to build one, as I could have got this wrong...
I read that it should only take maybe 4,000 Amp Turns to saturate any iron in a core of 1m length. The coil below provides almost 40,000 AT/m at 48W input power. So - I have over-specced the coil by a factor of TEN - so it could probably be smaller and still work well. Note input power is inversely proportional to the size of the coil - so bigger coil = less input power.
Core Cylinder Size: 150mm long, 50mm diameter
Central Fixed Core Length: 30mm
Armature Lengths: 30mm
Throw: 30mm
Coil Outside Diameter: 100mm. 1.5mm wire, 1600 turns, 3.53ohms. 13v = 3.7A = 39,000At/m
Almost 6Kg of copper!
Calculated output power at 1000RPM: 2,300 Watts (If you could get it to run at 10,000RPM - it'd make 23Kw.)
Input power 48 Watts at 50% duty: 24 Watts
C.O.P.: 96
Note: You could use permanent magnets for the armature parts. As they're only 50mm x 30mm - not too expensive. (Also, you can add steel to a magnet to make it effectively longer - so a 20mm thick magnet + 10mm steel is as good as a 30mm magnet)
Note 2: This is calculated with the armatures remaining fully within the core at all times. You could increase the throw easily by letting them partly exit the core at the extremes of stroke. This means a bigger crank, more torque...
Attached is a pic of a prototype design - based on the above specs - which I hope includes the best bits of both my & Luc's designs. Note: the shaft is attatched to the magnets, but slides through the central core - on a PTFE sleeve. The shaft needs one more set of sliding bearings at the crank end to hold it in position.
- It's to scale - so 150mm long, 50mm diameter, 30mm cores, magnets & throw
- Uses PMs, and has a magnetic shaft like Luc's
- Has a big coil, with central core - where all the action happens, like mine.
I think this is pretty easy to build. It would need an AC or alternating pulsed DC input - and would be 'single stroke'...
For the coil - assuming you have a power supply that can handle a range of voltages & currents - it would be a useful test to start with a smaller diameter, and add layers - to see what the difference it actually makes. So start off with perhaps 1Kg of copper, then 2Kg, 4Kg etc... More copper should mean less input power required for the same output...
Quote from: tim123 on July 27, 2013, 07:45:22 AM
Attached is a pic of a prototype design - based on the above specs - which I hope includes the best bits of both my & Luc's designs.
- It's to scale - so 150mm long, 50mm diameter, 30mm cores, magnets & throw
- Uses PMs, and has a magnetic shaft like Luc's
- Has a big coil, with central core - where all the action happens, like mine.
I think this is pretty easy to build. It would need an AC or alternating pulsed DC input - and would be 'single stroke'...
For the coil - assuming you have a power supply that can handle a range of voltages & currents - it would be a useful test to start with a smaller diameter, and add layers - to see what the difference it actually makes. So start off with perhaps 1Kg of copper, then 2Kg, 4Kg etc... More copper should mean less input power required for the same output...
Thank you Tim for taking the time to make this drawing and all the details.
I do have some 2 inch (51mm) diameter x 1 inch (25.5mm) thick N52 magnets
I also have a spool of 5 or 6 Kg. of 14 AWG (1.6mm) copper wire.
Questions:
Knowing this, if I stuck the magnets on 12mm thick steel cores (since the magnets are so thick), would the thickness of the center core need to change or the overall coil length?
Can the center shaft be magnetic and can I use a thin bronze sleeve bearing in the center core as guide?... or will this cause a short?
I was also thinking... if I use such strong magnets, would the core not have a powerful return stroke (center rest position) when the coil is switched off?... if so, maybe we can use this and maybe the fixed center core can be positioned off center of the coil so we would only need one power stroke and the return will be done by the magnets?... would this not be worthwhile?
Thanks for your help
Luc
Hi Luc,
the dimensions are not crucial. You can change any of them, within reason. I think the maximum effective stroke length is about 2 inches though...
Do your magnets have a hole in the middle? I'm not sure how you'd fix them to the shaft if not.
I'm not sure what you mean by 'if I stuck the magnets on 12mm thick steel cores'...? Assuming your magnets do have holes - you'd just need to get a shaft to fit through them, and a means to secure them to it.
Yes the shaft could be magnetic - i.e. mild steel. Yes, i think a brass sleeve should be ok, ptfe would be better but theres no danger of shorting.
This design has to be powered with alternating current (pref. pulsed alternating DC) - there would be no auto-return stroke because the magnets will stick HARD to the central core when the power is off. It has to be actively powered in both directions - unlike the non-pm design. The benefit of that is that it produces more power per revolution...
By the way - I would probably make this using two (or more) coils - so the central core can be fixed between them.
Important note:- long coils have strong forces between layers (due to the voltage difference) - and it's better to break them up into multiple shorter coils... See the book on solenoids for more details...
The central core could be almost any size - a longer one will develop a bigger, longer field, but as long as it's not too thin - it will work. I'd guess anything over 10mm should give decent results. It would ideally be made of laminated steel, but it'll still work with just a lump of mild. It'd just get hotter faster.
Quote from: tim123 on July 27, 2013, 10:09:46 AM
Hi Luc,
the dimensions are not crucial. You can change any of them, within reason. I think the maximum effective stroke length is about 2 inches though...
Do your magnets have a hole in the middle? I'm not sure how you'd fix them to the shaft if not.
I'm not sure what you mean by 'if I stuck the magnets on 12mm thick steel cores'...? Assuming your magnets do have holes - you'd just need to get a shaft to fit through them, and a means to secure them to it.
Yes the shaft could be magnetic - i.e. mild steel. Yes, i think a brass sleeve should be ok, ptfe would be better but theres no danger of shorting.
This design has to be powered with alternating current (pref. pulsed alternating DC) - there would be no auto-return stroke because the magnets will stick HARD to the central core when the power is off. It has to be actively powered in both directions - unlike the non-pm design. The benefit of that is that it produces more power per revolution...
By the way - I would probably make this using two (or more) coils - so the central core can be fixed between them.
Important note:- long coils have strong forces between layers (due to the voltage difference) - and it's better to break them up into multiple shorter coils... See the book on solenoids for more details...
The central core could be almost any size - a longer one will develop a bigger, longer field, but as long as it's not too thin - it will work. I'd guess anything over 10mm should give decent results. It would ideally be made of laminated steel, but it'll still work with just a lump of mild. It'd just get hotter faster.
Hi Tim, thanks for the reply
No, my magnets do not have a hole in them. What I was thinking is, if I use 12mm thick steel cores and weld them to the central shaft, then I could magnetically stick the magnets to the cores and add epoxy between then for extra hold. I can also epoxy another 12mm disk on the outside of one of the magnets if I want to attach a connecting rod or something to it.
I think this should be strong enough for basic pull tests.
Sorry, I forgot that if one of the repelling magnets would get close to the center core it would stick to it. So I agree, it needs AC to work.
I don't follow you about adding more coils so the central coil can be between them? ???
Thanks
Luc
Hi Luc, I'm pretty sure epoxy will not be up to the job... If your magnets were 1.5T, the max force on each could be up to 170Kg. The max force from the piston as a whole would be just over 200Kg.
Without a hole - the only way I can think of would be to fit the magnets in a pipe. With the central core in there too, but with a means to attach it so it doesn't move, but the pipe / piston can. The pipe would have to have slots cut in to allow it to move past the core...
K&J says the max force for 2" x 1" N52s would be 257lb
http://www.kjmagnetics.com/calculator.asp
(I just checked my force projections for these magnets against theirs - and my calcs look right)
I was thinking that if you made the main coil in two short sections - i.e. 75mm length, then it may be easier to fit the central core between them. It has to be firmly attached - as it's subject to the 100+Kg forces too... so you could make it like a '+' shape (viewed from the side) so it would fit between the two coils, and inside them a bit...
Hi Tim,
You wrote:
QuoteYou're right, and I've not included inductance & loss calcs because:
- I'm not sure how to do that
- the shorted coil could be replaced with a PM. I have no idea how many turns it would need at this stage...
Instead I've just multiplied the required ampturns by 10 - on the basis that if i plan to give it 10x more than it should require - then that should cover most eventualities. So where 800AT should saturate the core, I've gone for 8000AT... Note, It still goes OU if I increase the assumed power in by 100x, or even 1000x - just at a bigger size...
Well, the inductance of the coils is to be figured out first. Your example coil above has these data:
ID=50 mm, N=1600 turns, wire dia=1.5 mm (I used 1.48/1.5 uninsulated/insulated in the software, link below), coil length 150 mm, Rdc=3.53 Ohm
From this link, this gives about 56.3 mH inductance, its OD comes out as 98 mm, its Rdc=3.78 Ohm:
http://coil32.narod.ru/calc/multi_layer-en.html (http://coil32.narod.ru/calc/multi_layer-en.html)
Your earlier coil example for Case 3 setup has these data:
ID=100 mm, N=2178 turns, wire dia 3 mm (2.98/3), coil length=200 mm Rdc=3.23 Ohm
This coil calculates to have about 383.7 mH inductance, its calculated OD is 298 mmm and its Rdc=3.42 Ohm.
Now you have to calculate the so-called L/R time constant for the coil, it gives 0.0563/3.6=15.6 msec for the first coil and 0.3837/3.3=116.27 msec for the second coil (I used 'averaged' R values from your own and my link calculators).
Now you may wish to study this post here: http://www.overunity.com/8411/steorn-demo-live-stream-in-dublin-december-15th-10-am/msg360397/topicseen/#msg360397 (http://www.overunity.com/8411/steorn-demo-live-stream-in-dublin-december-15th-10-am/msg360397/topicseen/#msg360397) (notice: there is typo in the text under the LEGEND: Tau=L/R and not R/L) OR any other link (like this: http://www.electronics-tutorials.ws/inductor/LR-circuits.html (http://www.electronics-tutorials.ws/inductor/LR-circuits.html) ) on how the electric current increases in a coil from the switch-on moment to as long as the 5*(L/R) second elapses , after which the current becomes steady state and defined as the voltage across the coil divided by the DC resistance. Here I assume you switch a DC voltage source onto the coil but for AC currents similar considerations can be made.
This means that without the time constant consideration, taking especially the second coil example, the expected 3.9 A current (for your coil with Rdc=3.25 Ohm value) from a 12.7V DC voltage source could not be reached if you wish to run the engine at an RPM of say 960. Why?
920 RPM is 960/60=16 stroke per second for your piston setup i.e. 16 Hz, it is 1/16=62.5 msec, so the ON time for the coil would be as long as 62.5 ms (albeit this needs some refinements). However during this time, the current in the coil would not be able to reach the steady state value of 3.9 Amper but 1.6 Amper. See the formula in the d) part of the Example No 1 (almost at the bottom) in this link http://www.electronics-tutorials.ws/inductor/LR-circuits.html (http://www.electronics-tutorials.ws/inductor/LR-circuits.html) to calculate instantaneous coil current, using 62.5 ms for time t in the exponent. To force 3.9 A current under 62,5 msec time into this coil, you would have to use about 37V DC supply voltage.
Possibly, using several smaller value coil sections in parallel could help here (it should be tested) and it would be useful also to ease the strong mechanical forces that may occur within a single long coil as you mentioned above.
Regarding the estimation of shorted coil losses, I cannot address that topic, unfortunately, only practical measurements would give acceptable answers.
Greetings, Gyula
Hi Tim,
I see, so you think the coil will produce enough flux in the core that the magnets 350lb pull force to the cores would be cancelled and it would only be the epoxy holding the magnet. If so, I would agree that it would not be safe.
I now understand about the two coils. I think this would help get more coil flux to the center core.
Since it's getting more complicated with the magnets. What I would like to do at this point is make a mini version of your idea using the same coil I used in my last video. If with the same power it can pull more than 250g and hopefully much more! then I would be encourage to consider drilling holes in the center of my 2 inch magnets.
I hope you don't feel I don't trust your design. I'm just more of a physical experimenter and this will boost my confidence.
I'll get back to you with the test results
Thanks for your help
Luc
Hi Tim,
I took the day off of my houseboat building to build a mini version of your design variation using the same coil I used in my last video.
I used two 1/2 inch N45 cube magnets on the outside of each core.
Unfortunately, I could not measure any extra pull force compared to my design using the same two magnets on each end of a solid core of about the same mass as your 3 cores.
I'll now wait till you build your own to see how your results turn out.
Thanks for sharing and your time.
Luc
Hi Luc, sorry, I don't understand, could you perhaps take a photo of your setup? Or a diagram?
I made a typo with the 960 rpm (wrote 920) but in the calculation I again used 960 so no mistake in result I hope:
Quote...
920 RPM is 960/60=16 stroke per second for your piston setup i.e. 16 Hz, it is 1/16=62.5 msec, ...
Tim,
Regarding your setup in post Reply #9 ( http://www.overunity.com/13673/tims-magnet-piston-engine-design/msg366379/#msg366379 ) I would suggest a saturation test first for the central iron core as follows:
Before fixing the central core, a 10 to 40 turns of single layer test coil could be wound around it on its outside surface, (wire diameter is not important) and then insert this core+coil into the big coil as shown in the drawing.
An inductance meter (L meter) is to be connected to the single layer coil to see its self inductance. Then a DC supply voltage is to be connected to the big coil with the calculated current needed to saturate the iron core. Saturation is seen on the L meter as a drop in inductance for the test coil. Say as an example the test coil has 200 uH inductance when there is no input current in the big coil and it drops to at least a 10-15 uH value when the 3-4 Amper input current is ON for the big coil.
Gyula
Quote from: tim123 on July 29, 2013, 03:08:05 AM
Hi Luc, sorry, I don't understand, could you perhaps take a photo of your setup? Or a diagram?
Hi Tim,
I live on a sailboat in the summer as I don't have a home... and my lab is in a friends basement. So today I'm back at my boat and won't be going to the lab.
What I built yesterday is exactly the diagram you made for me on the previous page. However, in a much smaller scale so it can fit inside the coil opening I used in my last video. This way I could compare your design pull (using the same power) to my results.
The coil opening is a little more than 1/2 inch x 5/8 inch and the coil is 1 inch and 1/4 long. So a center core was made to fit snug in the center of the coil and two moving cores were made which were attached to a 1/8 inch round shaft that goes through the center core. The 3 cores are about 1/4 inch thick, so we have 1/4 inch movement in each direction.
I powered your design (without magnets) and got no movement. I then attached two opposing 1/2 inch cube N45 magnets (one on each core side) and got movement when the coil is powered.
Your design pull (before cores magnetically contact) was 60 grams which is double the result of my first test (with no outside cores) in my video demo using only two 1/2 inch cube magnets. However, I then realize I cannot compare your results to mine as my center core was 4 inches long and much of the two 1/2 inch cube magnet flux would be much lower, so less pull should be the result.
So then I removed your core design out of the coil and cut a 1 inch long core to fit the coil, this way the magnet flux to core volume would be a little more comparable. I attached the two 1/2 inch cube magnets to each end and powered the coil and got the same 60 gram pull force.
So unfortunately I cannot see the advantage, unless you are considering when your center core magnetically locks to the moving core, then it would have more pull force at that point. However, you then need to supply power to remove it, so I'm not considering that as a power gain. Is that wrong?
I hope you better understand the tests.
Thanks
Luc
Hi Luc, thanks for taking the time to explain. Interesting results.
I've been thinking about this whole approach, and I think I've realised that it can't go OU, the reason being Faraday's law, which I learned about recently, and now I get it...
This design is a motor / generator. As the magnets move to & from the center of the coil - it'll induce a voltage in the coil in opposition - so it'll take more power... This has to apply to a plain solenoid too. Live and learn eh!
However, the rotary version - I'm not so sure about...
Given a simpler version, without the coiled sections - i.e. just the plain steel, repelling sections - In that case, the magnetic field doesn't move relative to the center of the coil, but I'm not sure if moving the rotor relative to the stator would still cause the coil to see a change in field.
I'm going to have to think about it some more.
Gyula, thanks for all the info on the previous page - I'm going to read it thoroughly, and include it in my calculator. Your suggestion on testing the saturation point of the core is a really good one. Thanks.
Quote from: tim123 on July 29, 2013, 11:45:47 AM
Hi Luc, thanks for taking the time to explain. Interesting results.
I've been thinking about this whole approach, and I think I've realised that it can't go OU, the reason being Faraday's law, which I learned about recently, and now I get it...
This design is a motor / generator. As the magnets move to & from the center of the coil - it'll induce a voltage in the coil in opposition - so it'll take more power... This has to apply to a plain solenoid too. Live and learn eh!
However, the rotary version - I'm not so sure about...
Given a simpler version, without the coiled sections - i.e. just the plain steel, repelling sections - In that case, the magnetic field doesn't move relative to the center of the coil, but I'm not sure if moving the rotor relative to the stator would still cause the coil to see a change in field.
I'm going to have to think about it some more.
Gyula, thanks for all the info on the previous page - I'm going to read it thoroughly, and include it in my calculator. Your suggestion on testing the saturation point of the core is a really good one. Thanks.
"This design is a motor / generator. As the magnets move to & from the center of the coil - it'll induce a voltage in the coil in opposition - so it'll take more power... This has to apply to a plain solenoid too. Live and learn eh!"
Exactly. That law is what makes it merely an "energy conversion device". In order for higher efficiency, you must separate the generator from the motor.
Liberty
Quote from: tim123 on July 29, 2013, 11:45:47 AM
Hi Luc, thanks for taking the time to explain. Interesting results.
I've been thinking about this whole approach, and I think I've realised that it can't go OU, the reason being Faraday's law, which I learned about recently, and now I get it...
This design is a motor / generator. As the magnets move to & from the center of the coil - it'll induce a voltage in the coil in opposition - so it'll take more power... This has to apply to a plain solenoid too. Live and learn eh!
However, the rotary version - I'm not so sure about...
Given a simpler version, without the coiled sections - i.e. just the plain steel, repelling sections - In that case, the magnetic field doesn't move relative to the center of the coil, but I'm not sure if moving the rotor relative to the stator would still cause the coil to see a change in field.
I'm going to have to think about it some more.
Gyula, thanks for all the info on the previous page - I'm going to read it thoroughly, and include it in my calculator. Your suggestion on testing the saturation point of the core is a really good one. Thanks.
Hi Tim,
yes, I agree! ... it has a generator effect and if you remember I said that at the end of my video.
I will be experimenting with trying to find ways to reduce the generator effect.
One way could be with high voltage capacitive discharge, as voltage travels very fast in a coil and once the coil is disconnected it has no generator effect to speak of, compared to being continuously connected to a low impedance source like a battery or power supply.
I think this is what Ed Gray was doing but he had some kind of a circuit that we don't seem to have all the details on.
Keep up the research
Luc
Gyula, just wanted to thank you again for explaining that so well. I've added inductance, time-constant & transient-time to my calculator, and a lot of things I didn't get before now make sense. :-)
Liberty - Thanks for contributing. This is suggesting to me that any motor that's also a generator is - by it's nature - under-unity. I was just wondering if part of the key was to separate the two. Perhaps only a pure motor or generator has the possibility of OU...
Guys, can I ask you to help one more time?
Going back to the rotary version... That one is, I think, a pure motor. Remove the coil sections - so it's just repulsion between the iron rotor, and iron stator, then when the coil is powered, the two repel.
If the rotary version had a perm-magnetic rotor & stator - it wouldn't work as a generator - because the apparent flux to the coil would be constant. I think.
If the rotor was a PM, and the stator was iron, it would work as a generator, due to the iron stator being magnetised & demagnetised as the PMs rotate. However, in this design both are magnetised / demagnetised at the same time...
There's no movement of the flux axially in the coil, the question is does the rotation of the rotor inside the core, away from the stator bars somehow cause a generator effect in the coil? I'm struggling to see how it could.
New diagram attached for clarity :-)
So - can anyone tell me - If the coil's powered up, and the rotor is turned - does it cause any change in inductance / flux - does it cause any faraday-law generator effect - in the coil?
Hi Tim,
So far I have not had a look at the rotary version thoroughly because it was not fully clear for me for the first glance... Now that you redrew it, it is still not clear... Would you clarify first:
1) finally there is or there is not any permanent magnet anywhere in it?
2) there is or there is not a shorted coil ?
In fact where are coil(s) in the new setup? (I know there is the big coil all around the whole rotor and stator.)
As an addition, could you include the other coi(s) in the diagram (if there is any)?
This is not clear, I would like to understand your text from above post:
QuoteRemove the coil sections - so it's just repulsion between the iron rotor, and iron stator, then when the coil is powered, the two repel.
So what repels each other when the coils are removed?
One more thing: the magnetic poles of the big coil are utilized or its saturating effect on the rotor (or stator) core is utilized?
Thanks, Gyula
Hi Gyula,
1) No - there are no PMs in it, just the iron.
2) No - no shorted coil
There is only the 1 big coil around the outside.
The way it works is: When the coil is powered, the iron in the core becomes magnetised. The rotor and stator both repel each other because they are the same polarity. The rotor and stator both effectively become bar-magnets which run the length of the coil, of the same polarity - thus repel. (If you put 2 nails in a coil & power it up - they repel each other)
Pretty simple. When the power is switched off, they no longer repel (as much - there would be some residual magnetisation).
The big coil is therefore being used to saturate the iron.
So the power is switched on, just as the rotor goes past it's alignment with the stator. And switched off just as it leaves the stator - and is in alignment with the air gap.
I hope that makes sense.
Yes it makes sense now.
QuoteThere's no movement of the flux axially in the coil, the question is does the rotation of the rotor inside the core, away from the stator bars somehow cause a generator effect in the coil? I'm struggling to see how it could.
-If the coil's powered up, and the rotor is turned - does it cause any change in inductance / flux - does it cause any faraday-law generator effect - in the coil?
Yes, I think it can cause a generator effect while there is input current i.e. Lenz law must be valid but this must be much much lower than in a conventional generator. Because the rotor becomes a moving magnet during the ON time of the main coil and when the rotor shaft is loaded in these moments, a reaction effect should manifest back towards the primary source i.e. input current.
I also think that using an L meter across the main coil to monitor its inductance while manually turning the rotor, you could see a change in inductance (albeit a small change I believe) whenever the rotor comes out from the covering hence the 'shielding' effect of the stator plates. I mean the stator plates hide the rotor from the coil when the stator and rotor just fully facing each other and as you rotate away the rotor from this position more and more 'iron' area appear inside the coil. This needs to be tested of course but that is how I think. Again, this effect is also a small one, far from causing as much drag as Lenz does in a conventional setup.
I think both the shape of the rotor and the stator should be optimized to get the biggest repel force between them.
rgds Gyula
Hi Gyula. Thanks for your input. I think you're probably right. It is something I think I'll have to test.
I would have thought that the rotor & stator I'd drawn were pretty much optimised already, so I'm intrigued as to what you might have in mind..?
Update... I've done a basic test. Air core inductor. 2 bits of iron for the stators, 1 fatter bit for the rotor. With the rotor in alignment with the stator ('shielded') 5.80mH, with the rotor at right-angles to the stator 5.85mH - so yes it does make a difference, but only a small one...
It definitely looks like an idea worth pursuing to me at the moment. Any advice etc. gladly received. :-)
Quote from: tim123 on July 30, 2013, 10:50:18 AM
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I would have thought that the rotor & stator I'd drawn were pretty much optimised already, so I'm intrigued as to what you might have in mind..?
Update... I've done a basic test. Air core inductor. 2 bits of iron for the stators, 1 fatter bit for the rotor. With the rotor in alignment with the stator ('shielded') 5.80mH, with the rotor at right-angles to the stator 5.85mH - so yes it does make a difference, but only a small one...
It definitely looks like an idea worth pursuing to me at the moment. Any advice etc. gladly received. :-)
Well, just thinking of the repel force from the motor shaft direction: a mainly radially directed force is consumed by the sides of the shaft ball bearings unfortunately and the more tangentially you can direct the repel forces the more rotary torque the shaft can take up. This can best be achived by 'slanted' facing areas on both the stator and the rotor.
So this means the facing areas should be slanted such a way that the forces between them are mainly in a tangentially direction to the rotor 'outside circle'. If you need a simple drawing I will make one later.
Gyula
PS, Yes the change in inductance is small, even though in a real setup you envision the facing areas will be higher, causing a bit higher change: still small... :D
Thanks Gyula, that makes sense. What you're saying is that with the current arrangement - when powered on, most of the force is directed back towards the shaft...
I've been thinking about a re-arrangement of this design - to give more surface-area, and perhaps that solves this problem too. I'll do a drawing...
Ok. New design "Fin motor" - Drawing attached. In this version, the iron rotor & stator faces are arranged at 90 degrees to the last one. This is similar to one of those variable capacitors which have 2 sets of plates, one of which rotates.
In this design, the surface area is greatly increased between rotor & stator. I think, in this case, the rotor & stator will attract - because of the change in orientation... So when the coil is powered, the rotor 'fins' are attracted to the stator 'fins' - and I would imagine, would pull pretty hard. When it's de-powered, the residual magnetism will cause some drag, unless the coil is powered to the opposite polarity - just enough to demagnetise the iron - at the end of the power-stroke.
There should be virtually zero generator-effect as the rotor's movement hardly changes the inductance of the coil at all. So at full power, it should only take a little more electrical power than that required to saturate the core. Perhaps. From the coil's point of view, it's core is 're-arranging itself', it is symetrical though - there's no obvious moving flux as in a standard motor.
The forces should be largely tangential to the rotor - as the rotor fin is attracted between the stator fins. It would need to be well aligned though - if it weren't, and one set of magnets were closer, there would be strong pulsing forces along the shaft which wouldn't be good for the bearings or efficiency.
If every one of the fins, when saturated, acts like a magnet, then this motor should have a pretty high power density - it would be easy to have a really large surface area. As all the magnet faces are packed in together, with just one surrounding coil it's a lot simpler too.
What do you think guys? Am I on to something, or just missing something as usual? :)
Tim
PS - Soz if drawing not brilliant. I noticed I should have erased the circle around the rotor....
Hi Tim,
Well, your 'fin' motor really increses the surface area of both the rotor and stator and forces surely increase.
Question is: which direction?
I am afraid forces would cancel each other? I mean your rotor shape and stator shape have symmetry and the big coil wrappes them up fully from the outside, magnetizing them in a symmetrical way ? In your previous drawing the assymetry was insured by the fact that the rotor could fully leave the stator, in this setup it cannot. Perhaps omitting half of the rotor may already cause an assymetry to let forces act into a direction. I speculate here of course, this needs more consideration.
One more thing on your fin motor: the rotor iron core is embedded quasi fully into the stator, hence the flux from the big coil cannot easily penetrate and reach the rotor, to magnetize it?
I managed to dig out a drawing I made to Luc at another forum long time ago that shows facing slanted surfaces to increase shaft torque, see it attached. It shows the principle only, it must be adapted to your earlier drawing. IT was meant to increase the torque of a pulse motor where the permanent magnets are on the rotor and coils are the stators but in most of the cases these components are positioned radially with respect to the shaft, giving a reduced torque inherently.
rgds, Gyula
Hi Gyula, as the rotor fin enters the stator, the power goes on. It's attracted to the stator fins it's in contact with - the other set are an air gap away, and attracting the other half of the rotor. So the asymmetry is ensured by the timing.
The rotor does fully leave the stator - the fins go from being fully overlapped, to not overlapped at all.
My understanding is that the flux goes through the entire contents of the core, and it's not possible to shield it. The flux can't saturate the stator, and not the rotor too - even if they're together. Besides, even if it only saturated the stator - then the stator would still attract the rotor.
Thanks for the diagram, I didn't really understand what you meant until you posted it. It's not ideal though. I think in the 'fin motor' design the force is literally tangential to the radius... :)
Inefficiencies will always be inherent to moving mass in order to produce energy. A magnetic field is a 'virtual mass' in that it exerts the effect of a mass myriads of times it's own weight.
Since the dawn of man's recognition of the energy potential exhibited by the quantum world....he has chased after it. Largely via the relatively clumsy (by comparison) vehicles of our domain. Take massive electrical generators and internal combustion engines as examples. The energy required to accelerate and decelerate mass is a cost that those in the 'field' are increasingly weary of paying. Of course, they seem to think nothing of passing those costs (and much, much more) on to you. The fact that man has proven increasingly capable of employing the virtual to effect the 'real'....exposes our own 'virtual' state.
Case in point:
http://www.youtube.com/watch?v=LX7q--QLz1k (http://www.youtube.com/watch?v=LX7q--QLz1k)
Of course, when you think about it, all is "real". It is simply a matter of balance of"power" and Righteous Authority....
Then, what isn't possible?
To what extent is the validity of existence for the many states of matter? Consciousness?
Magnetic fields can move mountains....but the relative mountains that initiate them need not play such a 'heavy' role in their production....and the work they do.
TS
Hi Tim,
Here is a link to a picture which shows a socalled butterfly variable capacitor 'rotor' I assume you think of as your rotor in a possible shape: http://img.youtube.com/vi/wuLKX0j7mV8/0.jpg I uploaded it too below.
If yes, then let's place this rotor into the center line of a big solenoid as you drew in your drawing above. Let's not have a stator fin part yet.
Let's try to agree that how the big coil would magnetize this rotor as a whole? I think the individual plates will become very thin magnet plates, one pole on the closer surface we can see fullface (the 1st plate on the left end of the shaft) and the other pole is on the other side of this 1st plate i.e. the plates would become magnetized by their thickness direction. And so on for all the 12 plates. I do not think that any one plate would be magnetized diametrically.
What do you think? (if you did not think of your rotor shape like shown in the picture, please describe the differences)
Thanks, Gyula
Hi Gyula, yes that's exactly the shape I had in mind.
I agree - the magnetic fins would be magnetised thru their thickness, but that will result in the rotor & stator being strongly attracted. Just like a stack of magnets will line up.
This is also like a Reluctance motor - the rotor & stator will come together to minimise the flux-path length. So either way I think it should work. :)
Hi Tim,
You may be right, I possibly mixed up this rotor shape with Butch LaFonte's perpendicular magnetics and his tests with washers placed between two facing (NS) magnets. Obviously, in your latest setup the NS field orientation is shaft-wise while in Butch setup with the washers it is radial-wise hence the washers repel each other.
Butch's tests are in this link: http://98.130.116.247/shared/manager.asp?d=files\ButchLaFonte\Perpendicular%20Magnetics\Video_clips\ (http://98.130.116.247/shared/manager.asp?d=files%5CButchLaFonte%5CPerpendicular%20Magnetics%5CVideo_clips%5C) and I mean this video: BalanceTip1.mov (best if you download).
I have a question on your stator shape and drew a rough sketch. Will the stator have the wall thickness at all or it is just not erased in your original drawing fin-motor.gif (like the circle around the rotor)? I believe this is important because as I sketched it reminds me a kind of Faraday cage i.e. blocks magnetic fields to penetrate the inside volume... What do you think? (This is why I mentioned the stator screening the rotor the other day.) Somewhere the stator ought to be cut into two parts, just due to assembling issues with the rotor and the cut may or may not solve field blocking? Or you think this is not an issue at all, regardless of the stator 'cage' shape (the continuous wall thikness)?
rgds, Gyula
Hi Gyula, I have wondered about the wall thickness for the stator. I think the wall is a problem - not because it will block the field - but because any rotor/stator faces running axially will repel - so an outer wall will reduce efficiency. Ideally only the radial faces would exist. However, that does make it more difficult to build. Thinner fins = less axial faces vs radial...
The rotor & stator have to be strong - it's an engineering challenge. I'll give it some thought...
- The stator fins could be made of steel sheet, cut to the shape shown previously, with tufnol tube spacers between - to provide the spacing for the rotor fins. They would all have to be bolted together - down the length of the coil - and into the casing (non-magnetic bolts). Would lose considerable diameter this way though.
- Could use brass spacers, and machine them to key into the stator plates. Would lose less diameter that way...
- Stator could be made of brass tube, with steel fins braised in place.
- Could make each stator segment a separate coil. So the stator fins would be the bobbin ends. Easy to bolt together from the outside then...
So there are a few options I can think of immediately... I'll have to have think about it some more with a glass o vino... ;)
Dont worry about the area. You can focus on the circumference where the torque is strongest. That way the fins do not need to be so big, but narrower and stiffer. This will wash away the problems with magnetic stress that is pulling and pushing on the fins. Only 10 - 15% of the radius is neccessary to have fins. The magnetic flux will find its path through a more narrow path where flux density will be much greater plus that you have focused the torque as far from the shaft as possible. More power and better rigidity. Less inductance also means more power at higher rpm.
Vidar
Hi Vidar, thanks for your input. 10-15% of radius sounds reasonable. I am concerned about stresses on the fins (and axially along the shaft too)...
I guess - if less inductance is better - then only the fins should be made of magnetic material - and the shaft & supporting structures should be non-magnetic... I suppose less iron in the core = less inductance means less input power required, and lower transient time, hence higher frequency...
Thinking about it, I guess there's no benefit in in magnetising / demagnetising bits of the rotor which aren't facing the stator - it'll just result in lost power, eddy currents, heating etc.
:-)
Tim
PS: I've started a new thread for this design - as we're not actually discussing the piston design any more...
http://www.overunity.com/13692/core-rearrangement-fin-motor-open-tech-ou/