Hi,

Please study this link and then you can answer your question:

Tutoring, Physics, Physics Tutoring, Magnetism and Matter, Bar Magnet, Gauss's Law, Magnetization and Magnetic Intensity, Permanent Magnets and Electromagnets - Tutorvista.com

rgds, Gyula

Thank you for the link but it doesn't answer my question. In other words, could you point me at the obvious mistake? Thanks

ABC

No idea is stupid or dumb. It may not work just the way you want it to, but it could lead to something that does. All my ideas work great on paper, then I build them.
So, I recommend building it. There is no substitute for putting your ideas to the test. Even if it doesn't work you will have learned far more than just thinking about it. I've learned more from building complete failures than anything else.
Let us know how it turns out.

Cheers,

Ted

Ok, let me rephrase my question
Does it look good at least on paper?

ABC

Looks great in theory, but practically it will be difficult. Magnets are unruly and non linear. That bismuth shield will get sticky and switching will not be smooth or easy. Nothing will work quite like you think it will.
You will be required to have the patience of a saint to get everything balanced and working right (something I sorely lack), and even then you are going to have a hard time recovering all your switching costs. A magnet traveling back and forth for a short distance produces a surprisingly small amount of power.
Otherwise it looks like a winner.

Cheers,

Ted

Reply to ABC:

Hi ABC,

Bismuth is useful in levitation experiments because it is a diamagnetic material, which means that it will create a magnetic field in opposition to an external magnetic field such as a magnet. Therefore, inserting the bismuth plate at point #1 in your diagram will induce a magnetic field which repels the south poles away from the bismuth plate.

It looks like you want the like poles to come closer together when either plate is inserted, and to accomplish that you should use a ferrous metal plate or strip. To see this effect, simply hold two like poled magnet surfaces close enough together so that you feel the repulsion, and then place a ferrous metal strip or plate between them. The like poles will then both be attracted to the plate, even when directly aligned in a normally repulsive manner. To get the reciprocating motion that you want, you of course don't want the magnet ends to actually contact either of the 2 plates. I suggest that you try a simple experiment such as depicted in my crude drawing below. The blued portions are 1/2 inch diameter ceramic magnets such as purchased at Radio Shack (part # 64-1883), and the magnets are stacked together as shown with the end poles in the same manner as shown in your diagram. The outer stacks are held in position by the brown rectangular guide blocks. The central stack is located inside a short length of 1/2 inch pipe (copper is fine, and you get a close but free fit of the magnets), which has been capped at the ends. The green lines represent non-magnetic coil springs. You can see that currently the coil spring at the left end is expanded, and that is because a window (light gray area) in the ferrous metal strip (dark gray) is aligned with the magnets, allowing repulsion. The right end also has a window, but it is in the non-aligned (closed) position at this time. This causes the north poles of both the reciprocating magnet, and the right end stationary magnet, to be attracted toward the ferrous strip, and the right end coil spring becomes compressed. When the ferrous strip assembly is pulled in the direction of the arrow, the window at the right end comes into alignment with the magnets, and the left end window closes. The right end coil spring, and the repulsion effect, pushes the central magnet stack to the left, and attraction toward the ferrous strip at the left end continues the motion until the left coil spring is fully compressed.


You can cut a slot, the length of the copper pipe, to watch the reciprocating motion, or you can use clear plastic pipe. If your spacings are laid out so that you always have either attraction or repulsion in effect, and if the magnets are aligned nicely, then this will definitely work. You can construct the experiment without the springs and it will still work, but the magnets will take a beating as they strike the end caps, and this will reduce magnetism and make a lot of clatter. In addition to the springs, a felt pad can be used at both ends of the reciprocating magnet stack to allow further cushioning and quieter operation. Even though this will work, it is not by any means a perpetual device unless you perpetually move the windows in and out of alignment. If you can devise a way to do that automatically, by harnessing the motion of the reciprocating magnet stack, then by all means go for it. To accomplish that, while also producing useful work, will prove quite difficult, to say the least.

Anyways, good luck to you,

Rick

Hi ABC,

Just have seen Rick excellent answer and all I add is as follows.

When considering magnetic flux interaction with any material, it all boils down to the material's magnetic permeability. Air is considered as having a permeability of 1 (bad flux conductor, just think of air gaps in magnetic circuits) and all of the non-magnetic metals have a permeability of around 1. Bismuth has just under 1, hence it is called diamagnetic, it very slightly repels flux. This turns out from the link when you read about Faraday's bismuth test.
So applying this info, when you insert a bismuth plate at place 1 in your drawing, all what should happen is the middle magnet might get shifted say 0.01mm or less to the right (not to the left!). It would take to insert a soft iron plate of appropiate thickness (or any ferromagnetic material with high permeability) for the middle magnet to move to the left.

You may wish to read on a similar concept (i.e. inserting permeable material between two repel magnets or simply inserting permeable material into a magnetic circuit to fill the air gap) here:
Ecklin Stationary Armature Generator

Regards,
Gyula

Thank you

This is the most important discovery about magnetic generators. Now I (probably) even know how McFarland coil worked.

IT"S ALL ABOUT RE-SHAPING MAGNETIC FIELD LINES!

Thanks for the answer and for the link. However, my understanding was (probably wrong) that since bismuth repels magnetic flux, it would also cancel magnetic field to a degree. Therefore, the middle magnet should start moving toward the plate, no?..

ABC

No I do not think the bismuth plate cancels the flux to the slightest degree.
I think it can only very slightly repel it.
Permanent magnets are able to attract permeable materials (like iron, nickel) by creating an unlike pole in the facing (nearest) volume of the material.
Now if a material i.e. bismuth behaves in the presence of magnetic flux like a weak like pole magnet then can we speak about attraction? And you have the left hand side repel force from the first magnet on the left too to consider in the "movement".

It is true I have never tested your setup with bismuth but this is how I think.

rgds, Gyula

Well... according to this picture form the link above, it should negate the flux...


ABC

The picture proves the flux lines do not go through the diamagnetic material but pass next to it because air in this case conduct flux better than bismuth.

Putting it otherwise fluxlines are slightly repelled by bismuth and seek for nearest routes to join together. Bismuth does not cancel nor negate any flux.

still ? Instead of riding on words, why don't you do some tests with bismuth?

rgds, Gyula

You are correct, the lines will try to connect (or interfere in this case of the same poles). This is why I thought of putting magnets inside a bismuth tube with "windows" cut at each opposite magnet and alongside the middle (to attach some sort of mechanical switching assembly). This would solve to problem of magnetic lines "escaping" and also the problem of solving friction (the magnet in the middle should be suspended inside the tube).

As to building one, I'm a little short on $$

ABC

ABC[/quote]
Yes, using bismuth for the central tube could levitate the magnet stack inside it without friction. During the reciprocating motions, however, the levitation effect will become less stable, and even less stable when you attempt to attach a mechanical linkage to perform work.

As to the money problem, you could build an experimental model as depicted in my post #7 diagram for $10 or less. The magnets come in 5-packs @ $1.99 per pack, and the remainder of the materials you can probably salvage for free from odds and ends around your home, or buy at very little cost.

Rick