Magnetically suspended flywheel !!!

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hello and congratulations for this excellent forum.

Although I haven't made my turntable myself (I own the Swiss made 'a.a.s Gabriel' magnetically suspended t/t, same principals as the Verdier but heavier), I regard myself some sort of DIYer since I have made many modifications regarding the arm (Clearaudio Souther linear tracking TQi) and the t/t itself.

You can see some of these mods below:

http://aca.gr/paper02.htm
http://aca.gr/paper12.htm
http://aca.gr/paper14.htm

_________________________________________

Lately, I have an extreme dream to add to the 20 Kg platter, a very heavy flywheel of 32Kg rotating weight, doubling or tripling the rotational inertia this t/t platter already has!

Adding this, I am thinking to apply the same suspension philosophy, by inserting 2 large repelling ring magnets, (as the 'Gabriel' and the 'Verdier' platters have), below the main flywheel body, which by the way I want to rotate with a 140 RPM more or less rotational speed.

Making a search about magnets, I want to give you first some info, asking you if it would be better using Neodymium or rare earths magnets which seem to be stronger. Here is the info and please put your comments about possible pros and cons:


A. HERE IS THE INFO I GOT from a t/t manufacturer:
***************************************

Magnets used in big woofers are nearly always made of plain ferrite, and their strength relative to size is very poor, but they are relatively cheap. The dimensions you suggest they may be as little as £40 or so. They can also demagnetise when used in this configuration, so beware.

In the case of my turntable we used a very high power rare earth magnets, which are ultra, stable but cost me a whopping £2000/pair. to lift the 40 kgs they are smaller than your spec and only 8mm thick. It is also important to have them magnetized in the correct pattern, otherwise they can "cog" as they rotate.

It is cheapest if you can use a "stock size " magnet, which may be made in small production. I would expect to be able to supply you one of the better quality magnets close to your dimensions for around £500/pair if you want to do the job right first time.

I will also say that you should machine magnet back plates, and they will affect the repelling force significantly. Fitted them is a special job and can be VERY DANGEROUS. I think that if the two magnets in my turntable were to come into contact when in their back plates their would take around 300 kg, yes 300 Kg !!! If you got you fingers in the way, you would lose them!! BE VERY VERY VERY careful. You have been warned!

To have them made, I would need to know the required lift, air gap, and limitations on size, and also your budget. Sorry but that's the way it is. Or just experiment with the woofer magnets you suggest. Be careful though as they will be very brittle.


B HERE IS THE INFO I GOT from "EA Magnetics INC."
***************************************

Neo-35, Nickel Plated Ring
5.90"OD x 2.36"ID x 0.984"Thk.
Magnetized through the thickness
2 pieces @ $ 192.75 each


Here are some answers to questions I have asked them (about materials, dimensions etc.), after they gave me the above price quotation:

1. If we go thinner, the straight will go down. We are already working with the best material available. The thinnest we could go is 25 mm. to meet the lift requirement of 32Kg.

2. All of the Neo material is an-isotropic. This simply means that it is oriented during the manufacturing process, and must be magnetized in the same direction. All of the strongest materials are an-isotropic. As far as the magnetization goes, we were planning on magnetizing them straight through the thickness with one pole on the top, and one pole on the bottom. The magnets will repel each other and rotate smoothly. However, with type of magnetization, one magnet will not drive, or rote the other magnet with magnetic force.

3. The magnetization will last for very long time. There is no date on this, but some have been tested for over 10 years so far.


So, to conclude:

1. Please tell me Pros and Cons regarding this idea of adding a 32 Kg. Flywheel to a 20 Kg platter?

2. What kind of ring magnets (top and bottom) should I use for this huge 32 Kg repelling action I will need?

3. Where can I get them from?

4. Any other 'secret' you would wish to share.


Thanks in advance - Best Regards
 
Flywheel

Hi Chistos,
Your Gabriel looks very impressive, both from engineering and aestetical point of view. Seems like you managed to keep this level during tweeking/upgrading...
The first question regarding your flywheel: why so heavy? Such a mass rotating at 140 RPM must be perfectly balanced both statically and dynamically - next to impossible without special balancing machine. You have to make a flywheel rather high/thick to keep a desired mass, so dynamic balancing and lateral forces equilibrum became an issue. Not a simple task, and if you fail, additional layer of vibrations will be added to the main platter. Will the expected sonic improvement worth a mess? I remember one guy reported better results after he get rid of the flywheel on his TNT turntable...
Regards,
Michael
 
diyAudio Senior Member
Joined 2002
FLYWHEEL CRAZE...

Hi,

Michael,

I remember one guy reported better results after he get rid of the flywheel on his TNT turntable...

Wasn't that refering to the TNTs' "Electronic Fywheel"?
I assume you're talking about that particular VPI TT.

Christos,

I will gladly look into the detail of that beautifull TT, in the meantime let me tell you that I'm no big fan of having magnetically suspended platter systems.

I'll comment further soon.

Cheers and congratulations on your lovely audio website,;)
 
Machined in one pass ...

Originally posted by livemusic ... Such a mass rotating at 140 RPM must be perfectly balanced both statically and dynamically - next to impossible without special balancing machine ...
Agreed,

In fact, having to turn the platter at 45 sometimes, the 140 will become 200 rpm, so this may be a problem. This is why I am thinking it over and over again and just yesterday I have discovered this interesting forum to get some ideas.

The rotating part should be machined 'in one pass' and the axis should be about 20mm. in diameter - thick enough and not very long to avoid lateral forces, but still I think I will need a very accurate and calibrated lathe to do the job...

Anyway, let's wait for some other ideas...

Thanks
 
Re: Not an answer, but a question.

Originally posted by EC8010 This is the second DIY turntable from Greece that has appeared recently on this forum. Is there a reason for this? Are LPs particularly cheap in Greece?
Mine is not a DIY, I just made some tweaks on it...

Yes, you can find cheap vinyl records here in Greece as well as expensive but this has nothing to do with DIY or not.

By the way...

Another question occured to me:

Where would it be better to put the flywheel ?

close to the platter,
close to the motor or...
away from both
?

Cheers
 
Get me a drums kick...

Hello again, after 6 months I opened this topic...

I wish to report that my heavy weight-high rotation magnetically suspended flywheel for my Swiss hand-made aas gabriel t/t and its magnetically suspended 20Kg platter is ready and spinning...

In this Audio... Paper, there are about 35 pictures to enlarge and most of the technicalities of the flywheel design are described. I am also taking the chance to review my whole analogue set-up. So, I am covering the following subjects:
  • The current state of the analogue set-up
    The description of the t/t elements
    The flywheel project
    The finished analogue system set-up - Accessories
Listening comments and concluding notes will follow in a couple of weeks, after the break-in period, I hope they are ready before Christmas...

An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.



I simply just want to say that I wouldn't go back for anything in the world!!!

I get a big smile in my face when I still hear people talking about 'dynamic impact', 'stereo separation' and 'silence between notes', digital is supposed to beat analogue...


Enjoy the music
PS: I will try to get a drums set in my room and compare! (Better be a good one...) ;)
 
Hi Christos,
Thank you for sharing you unique experience! May be the most challenging tweak ever implemented! Very interesting and well documented report indeed.
Seems "the more mass the better" is unquestionable statement in TT world. Added rotation moment may have a major sonic effect, as you proved. And additional flywheel is definitely the way to "lift-up" existing TT, though hard to implement and rather expensive one. But considering a new design, I'd rather go for one piece super heavy platter with hybrid bearing: conventional ball bearing with reduced by magnets axial load. Verdier already did something similar, to best of my knowlege.
Regards,
Michael
 
diyAudio Senior Member
Joined 2002
Hi,

Has anyone considered, or tried, electro-magnets rather than permanent magnets. Wouldn't they have the advantage of allowing the amount of float to be adjusted?

Actually, from an engineering POV this would be much better as permanent magnets don't mimmick a "permanent field" at all, they are a "permanent field" when power is applied.

Just make sure you maintain contact with the central bearing or you have yourself a flying saucer.

Make that at least 10 lbs of contact pressure for energy release.

Cheers,;)
 
In this case ...

Thanks for your inputs and the flattering comments...

Originally posted by livemusic

...But considering a new design, I'd rather go for one-piece super heavy platter with hybrid bearing: conventional ball bearing with reduced by magnets axial load. Verdier already did something similar, to best of my knowledge...
Michael,

You are right it is better, mass to be in one piece rather than 2, connected via any kind of thread(s). (Only problem I see is that you have the motor still directly connected to the platter)

But here, in my extreme case, we are talking about a 78Kg-33.33RPM rotating equivalent mass platter (if you wished to make it in one piece that is...), which I very much doubt if you can elevate it with any kind of magnet.

You will obviously need, as you indicate, to have an additional bearing, but IMHO bearings always introduce friction, believe me (How much of the 78Kg can you elevate with a magnet???). There is no way a friction bearing to be equalled with a magnet repulsion bearing what so ever.

TL Acoustics reported to me that the biggest improvement they got from their t/t design was the swift from the ball bearing, they have been using before, to Neodymium magnet bearing! But we are talking for a 9.5Kg platter NOT a 78Kg platter...

Also to my knowledge Verdier uses a completely magnet elevated platter (unless he has introduced a new model) as Hanspeter Gabriel does as well (only thing, aas gabriel platter is heavier: 20Kg).

To conclude, IMHO, for such mass we are talking here, high rotation high mass, totally magnet elevated f-w, is the way to go. But you have to have good engineering to not create additional problems as you presume and placement of the flywheel in such cases should be on separate shelve (independent rack is even better, see Forsell ‘reference’) from the platter's.

BTW, you don't need a special balancing machine, just a good calibrated lathe and good hands...

Originally posted by innernerd

Has anyone considered, or tried, electro-magnets rather than permanent magnets. Wouldn't they have the advantage of allowing the amount of float to be adjusted?
One advantage of using f-w is to completely isolate the pulsing of the motor to the platter’s rotation. Or, to put it in other words, to make the analogue even more analogue without the periodical (falls in the acoustic spectrum) noise of a motor...

That means, using an electro-magnet for repulsion, you introduce - you digitise so to speak, the rotation of the flywheel...


Regards
 
I have a dream...

Hi,
Hybrid bearing does not have to be based on magnets use. Pressured air cushion is easier to implement (especially if you already have an air bearing arm:) ).
My vision is pictured below. Air is supplied into the cavity between the upper platter with the attached ring and piston/ball bearing housing. Radial gap of 0.1 mm between them would be sufficient to keep air flow low. About 20 psi air supply will be enough to support 50 kg platter nearly "airborne", leaving 2-5 kg of the bearing axial load, just to sink platter vibrations and to provide perfectly rigid base for the record. The flywheel heavy brass (?) ring of the larger than record diameter is attached underneath the main platter. Two motors are used: one of direct drive type (old DD TT?) hidden under the platter, is supposed to accelerate and slow down the platter; it is swithed off when the speed reaches about 32 RPM. The second motor/belt provides constant rotational speed.
Just a dream, but one day, who knows..
 

Attachments

  • ultima.jpg
    ultima.jpg
    32.1 KB · Views: 930
Splendid!!

Splendid Michael!!

I wish you have more dreams of this sort - who knows - may be somebody will turn it to real ;)

My dream came true after a couple of years and your design (more complicated!) will need more I think... :D

Never the less, as far as the 50 Kg platter, mine also I do not believe it is more than that.
78Kg is the theoretical but as you understand, due to thread connection and not being all in one piece, you loose some energy. But, as I said, platter not being connected directly to a motor is a plus IMHO.

I wonder, why even this small 2 - 5 Kg on the bearing is needed? Compressed air gives any kind of vibrations or what?

Keep up with the good work (dream...)
 
Why stifness is important?

skaloumbakas said:

I wonder, why even this small 2 - 5 Kg on the bearing is needed? Compressed air gives any kind of vibrations or what?

Hi Christos,
Two resons for it:
1. "Pure" air bearing requires very tight production tolerances, the requirement, next to impossible to meet "on the kitchen table". The hybrid one can tolerate 0.1 mm - not a big deal. No vibration is induced by air if simple surge tank is used. High pressure, small gap air bearing is very stiff - excellent stuff indeed, exept one thing - see para 2.
2. Cart induces enormous amount of vibration when tracking the groove (one can listen to music with sthetoscope, placed near poorly damped tonearm, when amplifier is off). These vibrations will be partly absorbed/damped, partly bounced back to stylus, distorting the sound signal. The more induced vibrations will be absorbed, the less distortion you get. More compliant material using for the platter have better damping properties. From the other hand, compliant material does not provide enough support for the record - micro movements cause even worse distortions (that's why soft mat gives boomy bass).
Therefore, the platter has to be made of rather stiff material, having limited damping. Consequently, the sound wave should be allowed to propagate certain distance, ideally close to quater of the wavelength, to be effectively absorbed. Think about 100 Hz sound wave, having the wavelength of several meters, and you get the idea. Such platter is not a dream anymore, it's a nightmare.
So, though the compromise is unavoidable, let's give way for vibrations. The rigid pinpoint contact provides perfect path for vibrations, just like electrical jumper for grounding. One-ball bearing, like audiophile spikes, is working this way. The minimum axial load should be applied to the bearind, if you want induced vibrations to be sunken by downlaid components (plinth, shelf and so on).
Just plain physics.
 
Best for threads to turn this monster?

Fair enough...

Now I am in the phase of trying to establish what would be the best for my 'heavy case', regarding the material to use for threads - belts.

I have tried the following so far:
  • Dental floss (very good but makes some physical noise).
    Fishing string (lasts for ever but slips).
    Rubber O' Ring cords, cut in appropriate lengths and glued at the ends with special glue (the 1.5mm OD thickness is excellent but after some hours of turning, it breaks apart at the connection point).
    Didn't try silk threads because I think they are slipping.
I put a link to http://aca.gr/paper37.htm just in case some of you want to recall what I am talking about.

What is your experience regarding the above please?

Thanks and Merry Christmas to all...
 
I'm second for mylar tape. Well regarded manufacturers of DIY-style TT (Teres & Redpoint) came to conclusion mylar type is the best. 1/2" tape should give you enogh friction, providing all three rotating axles are perfectly aligned and you are not inducing excessive bending moment (lateral force) to your motor axle - should be checked against manufacturer spec.
BTW, I wonder how do you control the belt's tension? To say least, once three components are placed, the tension could vary with the time, temperature and so on.
Regards,
Michael
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.