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 Luc, sorry, I don't understand, could you perhaps take a photo of your setup? Or a diagram?

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.

"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

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...

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:

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.   

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 

Yes it makes sense now.

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.

-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

...
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...