hi guys, whilst dithering about thinking about what to do next, phono stage (yes) 6s4s pp amp (yes at some point) and various other meandering thoughts on what to persue and what not to, i had an idea for a magnetic suspension system for a plinth. i believe pro-ject have done one but other than that i could only find reference to magnetically suspended bearings and schreoder type arms. the idea is to use 2 large ring magnets and 2 small neodymium magnets per suspension unit in a 'turret'.
each will have a ring magnet at the bottom with a pillar going up through the middle of it, then a neodymium magnet on the top of said pillar. 4 of these will be on a tubular aluminium frame (one in each corner) with the motor attatched to it, spiked into a large slate slab. the top plate will have large ring magnets on the underside with the pole opposed to the ones on the frame to float the the top plate. there will be holes for the pillars to go up through so it drops over and floats above the underframe. there will be hollow turrets on the top plate that the suspension pillars go up into, with a small neodymium magnet in the top, oriented so they attract to the one in the top of the pillars. these are there so that they 'centre' the top plate above the turrets.
i dont know if these will be needed tbh, i added them to my drawings to correct for any pull between motor and platter. it'll be a belt drive this time as an idler would give a path for vibrations to get directly from the motor to the platter and defeat the object. a dd again would be pointless as isolating the arm from the platter would slightly change the vta and offset every time there was movement in the upper section.
any comments? i dont know too much about the effects a magnetic field would have on the cart and wiring, do folks reckon this is worth persuing?
a magnetic suspension system
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andrew Ivimey
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#2
Lovely idea and it need not necessarily affect the cartridge - how strong would the field need to be to keep the turntable assembly 'floating'?
OTOH, it is prob. too difficult to achieve without it affecting the cartridge and that would sound v.unpleasant.
might give a nice 'airy' character to the sound.
OTOH, it is prob. too difficult to achieve without it affecting the cartridge and that would sound v.unpleasant.
might give a nice 'airy' character to the sound.
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Mike H
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#3
You may find it completely impossible to do that way, read this:
http://en.wikipedia.org/wiki/Magnetic_levitation
http://en.wikipedia.org/wiki/Magnetic_levitation
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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cressy
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#4
cheers for the link mike, on reading it it appears that the problem would be lateral stability rather than actually floating it. the small magnet at the top i put in to try to counter that effect as the 2 magnets attracting each other will centre themselves might do it, but it appears that it might not be enough. hmmmm
im more concerned about the effects of the magnets on the cart. i had a look at the magnetic field using paper and iron filings last night and the small magnets i have seem to have an effective 'radius' of about 5 inches across. a short arm (rb250 mayware formula 4) should be ok as the cart would be outside this radius apart from at rest. the problem is the front right hand pillar. the ring magnets will have a larger but less concentrated field (ferrite instead of neodymium) the plinth itsself will be as large as i can make it given the space constraints. i'll still try this i think as it wont cost very much to try!
im more concerned about the effects of the magnets on the cart. i had a look at the magnetic field using paper and iron filings last night and the small magnets i have seem to have an effective 'radius' of about 5 inches across. a short arm (rb250 mayware formula 4) should be ok as the cart would be outside this radius apart from at rest. the problem is the front right hand pillar. the ring magnets will have a larger but less concentrated field (ferrite instead of neodymium) the plinth itsself will be as large as i can make it given the space constraints. i'll still try this i think as it wont cost very much to try!
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Mike H
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#5
The way I understand it, and vague memory of playing about with magnets in science classes etc., the instability problem is where two magnets repel each other OK, but then keep wanting to "slide off sideways", there's nothing to keep equilibrium on a central line.
You had the idea of tubes within tubes, only way I can see of doing it is if the inner was a steel rod, a ring magnet around its base, it's then 'North' or whatever. Then a same sort of ring magnet somewhere up in the tube, the rings repel and the tube is pushed up the rod. Also because the rod is magnetic as well the upper ring tries to push the rod away but equally all around, so suspends itself centrally without touching. That would be an equilibrium.
What bothers me is if it's such a great idea why can't you buy a commercially ready-made one.
You had the idea of tubes within tubes, only way I can see of doing it is if the inner was a steel rod, a ring magnet around its base, it's then 'North' or whatever. Then a same sort of ring magnet somewhere up in the tube, the rings repel and the tube is pushed up the rod. Also because the rod is magnetic as well the upper ring tries to push the rod away but equally all around, so suspends itself centrally without touching. That would be an equilibrium.
What bothers me is if it's such a great idea why can't you buy a commercially ready-made one.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
