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Author Topic: Tim's Magnet-Piston Engine Design  (Read 31536 times)

tim123

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Tim's Magnet-Piston Engine Design
« on: July 26, 2013, 01:38:01 PM »
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...


tinman

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Re: Tim's Magnet-Piston Engine Design
« Reply #1 on: July 26, 2013, 03:35:28 PM »
Like this one in the video link
http://www.youtube.com/watch?v=tM_HRwqKzFk

tim123

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Re: Tim's Magnet-Piston Engine Design
« Reply #2 on: July 26, 2013, 03:50:34 PM »
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.

gotoluc

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Re: Tim's Magnet-Piston Engine Design
« Reply #3 on: July 26, 2013, 04:02:24 PM »
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

tim123

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Re: Tim's Magnet-Piston Engine Design
« Reply #4 on: July 26, 2013, 05:07:02 PM »
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 ;-)

tim123

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Re: Tim's Magnet-Piston Engine Design
« Reply #5 on: July 26, 2013, 07:33:31 PM »
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.

conradelektro

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Re: Tim's Magnet-Piston Engine Design
« Reply #6 on: July 26, 2013, 08:40:37 PM »
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



tim123

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Re: Tim's Magnet-Piston Engine Design
« Reply #7 on: July 26, 2013, 08:59:22 PM »
Hi Conrad :), yeah, quite similar indeed... Magnapulsion sounds a bit better than MagPis too...  ;D

tim123

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Re: Tim's Magnet-Piston Engine Design
« Reply #8 on: July 27, 2013, 09:40:56 AM »
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...

tim123

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Re: Tim's Magnet-Piston Engine Design
« Reply #9 on: July 27, 2013, 01:45:22 PM »
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...

gotoluc

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Re: Tim's Magnet-Piston Engine Design
« Reply #10 on: July 27, 2013, 03:26:46 PM »
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

tim123

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Re: Tim's Magnet-Piston Engine Design
« Reply #11 on: July 27, 2013, 04:09:46 PM »
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.


gotoluc

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Re: Tim's Magnet-Piston Engine Design
« Reply #12 on: July 28, 2013, 05:29:31 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

tim123

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Re: Tim's Magnet-Piston Engine Design
« Reply #13 on: July 28, 2013, 10:27:21 AM »
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...

gyulasun

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Re: Tim's Magnet-Piston Engine Design
« Reply #14 on: July 28, 2013, 02:51:57 PM »
Hi Tim,

You wrote:

Quote
You'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

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 (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 ) 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  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