11.5Kg high rotation flywheel, for a 20Kg platter, both magnetically levitated!

Not the kind of mild (ceramic?) magnets Hanspeter Gabriel of aas gabriel - Switzerland and Verdier - France use in their designs.

Christos

Can't see it making any difference what kind of magnets are used, a magnetic field is a magnetic field.

There is!!!

Neodymium magnets have a very strong and concentrated field along the N-S axis and this is what I use for levitating my DIY custom flywheel. Cartridge with a Neodymium magnet underneath is simply lost if approaches the platter's spindle!!!

Ceramic (or other) magnets exhibit a broader magnetic field distribution, which does not affect the cartridge anywhere found itself on the surface of the record.

Total levitation force might be the same but the first is produced by a concentrated field in the centre and the other by a wider distribution field.

BTW, I don't want to sound paternalistic but please, read the paper carefully and make any comment after you digest it a little bit...

Cheers

Christos Skaloumbakas

President of the
Audiophile Club of Athens
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Thank you so much for sharing this. I looked over the paper and will not pretend to understand a wit of it And I will not barrage you with "but... but..." questions.

Just thank you for sharing your project with us.

- GregB

Insert Witty Signature Line Here

It would have been nice to have had the paper and website available in black text on white background as an option. Your delightfully busy blue background with white text had me reaching for the largest text button and I still couldn't read it without difficulty.

So perhaps you will be paternal and forgive me if I ask: Why a massive flywheel driving the platter by the equivelent of a couple of horse hairs should offer any benefit except more mass to fend off micro-seisms in the support structure? Which could just as easily have been added as unmoving mass. You admit yourself that it takes a day to get up to full speed. Is the flimsy drive connection even able to "see" the increased rotating mass of the flywheel?

Nime

Everyone has the right to be wrong.

Thanks for your remarks.

You certainly got the point but this is exactly what I am doing:

Since I don't want to 'see' the motor, I have only one belt connecting the motor with the flywheel.

BUT, because I want the platter to 'see & FEEL' the flywheel (I mention that twice in the paper...) I connect them with 5 belts.

So, what I am trying to do is to have platter and flywheel almost act as one body (you can feel it with your hand if you try to block the rotation putting your finger to the perimeter of the platter - you certainly feel that you almost cannot do it even a bit to reduce its speed and the cartridge surely loves that - that's where the dynamics come from!)

On the other hand, I almost took the motor out of the game (it is just maintaining the speed, through its flimsy 'horse hair' as you say, because I do not want its noise etc. (Even the best quality DC motors and p.su's have noise and speed instabilities and inaccuracies and everything...) Nothing can beat a 375rpm 11.6Kg rotating flywheel + a 33rpm 20Kg rotating platter.

Cheers

Christos Skaloumbakas

President of the
Audiophile Club of Athens
__________________
Web: http://aca.gr
Forums: http://aca.gr/forum/index.php
My system: http://aca.gr/pop_skal.htm

Super Magnets and where to get them Gaussboys, the FAQ is worth a look.

Via metafilter

Roy

quote:

---

Originally posted by skaloumbakas:
There is!!!

_Neodymium_ magnets have a very strong and concentrated field along the N-S axis and this is what I use for levitating my DIY custom flywheel. Cartridge with a Neodymium magnet underneath is simply lost if approaches the platter's spindle!!!

_Ceramic_ (or other) magnets exhibit a broader magnetic field distribution, which does not affect the cartridge anywhere found itself on the surface of the record.
Total levitation force might be the same but the first is produced by a concentrated field in the centre and the other by a wider distribution field.

---

Sorry Christos, but a magnetic field drops off (decays) at a rate of 1/r**2. All magnets exhibit the same rate of decay and same magnetic field dispersion if there are no outside influences. NIB (Neodymium) magnets may have a larger/stronger magnetic field per unit area than other magnets of a similar size and shape, however, the magnetic field lines are the same, the only difference is the strength of the magnetic field created. The N-S pole orientation of any magnet (including the Earth, which is a very large dipole magnet) produces the strongest magnetic field effect along this polar axis.

The physical shape of the magnet (washer/donut shaped, coin shaped, cylinder shaped, ball shaped) is what can alter the magnetic field created, but only marginally. Again, this holds true for all magnets.

The "shape" of a magnetic field can also be altered by the presence of other magnetic fields (either naturally occuring or created by electrical currents) and different materials with different magnetic properties.

If you have a technical paper on the distribution of magnetic fields from NIB magnets that illustrates/discusses a magnetic field characteristic to these magnets, I would be most interested in a copy.

Cheers

Geofiz,

I am very glad from your remarks

Maybe I was not clear to you (still...)

In order to lift a certain object (20Kg for example) with a couple of magnets, there are 2 different approaches.

You can either choose a large but weak (so to speak) ring magnets or choose smaller but stronger ones to achieve the same lifting total capacity.
(I am talking about ring magnets because you have the rotating axis of the platter to pass through...)

The first solution is not so convenient, as far as the construction stage, (it gives you less design options to play with), BUT since they are larger (have more repelling surface) and weaker, the magnetic force to any certain point on the platter (record) per surface unit is LESS (more but weaker magnetic lines pass through a greater surface). In other words the magnetic field is more evenly distributed!

The second solution gives you the same repelling action but the magnetic lines are passing through a smaller area - obviously towards the centre - because the magnets are smaller this time, (smaller OD - BUT stronger), meaning that there is a certain danger area on the platter for your precious coil cartridge to be... Extensive tests with different shapes and strengths and thickness and OD's and ID's must perform not to get caught in a difficult situation…

Tests and many peculiarities of Neodymium magnets regarding the magnetic field distribution and strength of various sizes and shapes and Grades cannot be found in textbooks (I see you are a Geophysicist - I am a Mining Eng myself with a MSC in Petr. Eng. from Imperial College - London) but knowledge can be achieved by playing with them and testing (mind your fingers though!!!) and getting in touch with various magnet manufacturers I NEVER SAID THAT THE FLYWHEEL PROJECT WAS AN EASY ONE...

And to be honest with you - there is a way that platters can be lifted with Neodymium magnets as well ('TL Acoustics' - Hellas), if you choose the correct Grade, shape, number etc. of them and the correct distance between the record and the top magnet - I will leave you thing about it, but I will not come back on this.

Enjoy the music
PS: I once had an LP12 with full options at the time – days to remember...

Christos Skaloumbakas

President of the
Audiophile Club of Athens
__________________
Web: http://aca.gr
Forums: http://aca.gr/forum/index.php
My system: http://aca.gr/pop_skal.htm

quote:

---

Originally posted by skaloumbakas:
Not the kind of mild (ceramic?) magnets _Hanspeter Gabriel_ of __aas gabriel__ - Switzerland and _Verdier_ - France use in their designs.

Christos

---

well, with the Verdier, there is a tracking force difference around one rotation of about +- .3p on certain cartridges like Ortofon SPU according to position, this is definitely too much. Also, if you dispense the string, you can "feel" a preference for one position of the platter.

kind regards,
Hartmut from Munich,
former Verdier owner
now owner of Pluto 10A turntable

Dear Hartmut

Thank you for sharing this info.

This certainly doesn't apply for aas gabriel .

Even with the minimum friction the gabriel platter exhibits (9 minutes to stop from 33.33RPM without belts attached), whenever you place the platter in relation to the bottom magnet it stays THERE STILL, without any preference what so ever.

Also, I have not experienced any tracking force difference around one rotation but then I am using a parallel tracking arm and I am not sure what exactly do you mean.

On the other hand I have heard strange things about Verdier that when it rotates, it vertically vibrates (slightly...) along the platter axis. IS THIS TRUE??

Also, could you tell us what is the suspended weight of the Verdier's platter and the time needed to stop from 33.33 without the string attached? (I want to understand its friction)

Thanks

Christos Skaloumbakas

President of the
Audiophile Club of Athens
__________________
Web: http://aca.gr
Forums: http://aca.gr/forum/index.php
My system: http://aca.gr/pop_skal.htm

[This message was edited by skaloumbakas on SATURDAY 10 January 2004 at 03:19.]