zero cost magnetic isolation

wow ...quite sophisticated

 

Mosfet's right on the money: Google for 'Earnshaw's Theorem' .

Stable levitation with fixed magnets (and no other external forces) is impossible.

 

I think that's understood. Its more a question of what minimal external force needs to be applied and how to make a stable and effective DIY platform.

 

That's far more difficult. The repulsion varies as dist^1/3, so even small drifts 'off centre' (of the magnet config provided) can lead to rather larger 'centering' forces being required than might be obvious. I doubt there's any solution short of F.E. analysis

 

http://home.earthlink.net/~lenyr/levmag.htm

this guy doesn't think so

 

I did post a link to the Gadget Shop back on page one. One way to circumvent Earnshaw's Theorem and achieve true levitation is to use electromagnets with microprocessor control of the magnetic fields. I have seen toys which do just this, to suspend small objects, sold in places like the Gadget Shop. I've also seen devices with more powerful electromagnets capable of levitating bottles of wine (for shop displays). Perhaps it would be too difficult to build something from scratch, but it could be done.

 

That's diamagnetism - not quite the same thing at all; Earnshaw still holds.

Besides which - to make the combo work with a CD player or similar in the way would require some seriously impressive magnets.. of an order that would buy a lifetimes enjoyment of live music at your home. Sod 'hifi'...

 

Felix, the point isn't to achieve true levitation, it's to try and achieve a degree of isolation, such as with the magnets with a hole and a rod. There are commercial products which achieve this, such as the Magix units that Clearaudio do. I don't think it needs to be perfect levitation to be worthwhile.

 

That's quite true enough. But even if 'perfect levitation' were possible I'm not sure it's actually desirable. You'd effectively have an undamped spring-mass system that would tend to 'ring'. There'd always be a commensurate amount of damping required.

If this comes from the restraint systems necessary to enable magnetic levitation that's no bad thing. I'd just prefer it to be intentional, not accidental

 

Total cod's......

its just no one has worked out how to do it ....

you have just got to think back to mosfets great grand father wispering in wilbur and orvills ear ....


Why not make a positve contribution to the thread...and if you can do that what exactly is the point of your comments ?

The magnet don't need to be huge ....6 x 10mm dia neodymiums are holding up my 99cdp at this moment ....admittedly with less than 2mm gap ...but the effect is easy to hear.

To achieve the unsuported isolation, I imagine you would need some sort of shaped magnet to provide the cup shaped magnetic field.....infact the ring magnet shown in uncle ants pic might just hold the clue.

 

deleted as wrong post

 

To be fair Pete, that Yamamoto magnetic thing uses the Teflon rod in between to apply the external side ways force needed to stop the top sliding sideways.

 

I seem to be being taken out of context ...

I've no problem with external forces .....as long as they don't destroy the one thing your trying to achieve.

I have no knowledge of how the to achieve a self supporting platform ...

my own effort uses three rods to keep the top plate from sliding off ....

all I can say is that you can hear the effect it has ..so its worth pursuing the design further.

has anyone tried dik's idea ?

 

Oh its definitely worth pursuing. Re externalforces, I think Felix and you may actually be in agreement here. As he says it could well be that a true self supporting platform may actually be worse.

One thing I am wondering ... I know nix about magnets ... is there some measure of magnetic strength that can be used to calculate what weight two opposing magnets will bear before being forced together?

 

sorry felix may have read your reply the wrong way ....

just tried a ring of nine [ 120mm radius] with a ring of nine opposing ....using mdf sheet with insets cut for each magnet. A sheet of 2mm perspex over the top ...very pretty but didn't work .....

the 4mm total of perspex is keeping the magnets too far a part.

I've now tried the magnets screwed to the perspex....nice bounce but wont take the weight ?

As to strength ....magnetic field strength .. in teslas ? but not certain how to convert that to kg

 

ok reverted back to the original mode ....ie rod up through the center of the magnets one opposing the other ....

with the cdp in place this provides a 1mm gap between magnets and allows a slight bounce .....using the stethescope isolation is cutting the high freqs from getting into the cdp [if the shelf the unit sits on is tapped]. I think this is as far as this version goes !

though a quick and dirty effort.... it works rather well and proves the principle is viable. I've already ordered some 25mm disc magnets !

 

Where are you getting the mganets from Pete?

 

ebay item number ...110132327223

but I'd suggest getting larger dia ones ...

I got ones with holes so I could use them else where if the idea was a failure....

 

Pete,

Those magnets are a claimed 3kg strength. No one has come forward with any equation to measure how much two opposed would hold (obviously minus the small lateral friction!). Do you think a pair of those is anywhere near holding up 6kg?

I have moved off BBs on oak to pure ebony, temporarily (maybe).

Ian

 

Forces

Ok,

I'll answer my own question, or rather Kevin of Emovendo magnets, US will;

The repel force between two magnets is approximately 2/3 of the pull force.

So, three pairs of the 100Kg jobbies should support a nice tripod equipment stand full. Just cut round wooden support legs, glue the magnets to the cut off parts and cut a ptfe/water pipe sleeve sealed at the bottom to guide the legs and fill with silicon to damp it.

Or repeat between layers using lighter magnets for complete isolation.

Ian

Just remember, don't go anywhere near it with a pacemaker. Inviting a visitor to swap a record over on such a rack could end in disaster.