Magnetically suspended flywheel !!!

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#21
Hi,

should be checked against manufacturer spec.
Click to expand...

Yes, some of the Maxxon DC motors seem to be notoriously fragile in that department.

BTW, I wonder how do you control the belt's tension?
Click to expand...

IMHO the easiest way is to have a heavy motor pod that you can move forwards and backwards.
Sometimes a sliding rail with a locking nut is used for this.

Cheers, 😉
 
#22
Rubber O' ring belt a clear winner?

Thanks,

Tape drive: I have tested the 1/4 " reel to reel, if this is what you mean, and failed to grasp (slips all the way...). Torque needed to rotate the flywheel is extremely high (the 10mm OD motor capstan 'sees' a 45mm. OD flywheel drive!). In fact I had been using tape with my previous configuration - and there are some sonic advantages - but now this is a complete different story.
BTW, if you noticed within the paper, I am referring to that and in fact the first configuration of the flywheel drives was machined for tape to be used, but failed - see paper (under 'Flywheel construction')

Belt tensioning: I am referring also to that in the paper (under 'Energy absorption - drainage')...
  • For motor to f-w belt tensioning, I use the swivel of the tripod used to be placed on (the motor spindle is off-center to the motor heavy housing, so by rotating the tripod base, the motor capstan moves away or close to the f-w.

    For f-w to platter belt tensioning (and alignment), body + rot. bell of the flywheel is 27.5 Kg heavy, so I can slightly move it on its shelve, as the previous gentleman suggested.
As far as the drive type is concerned, it seems that the 1.5mm OD rubber O' ring cord is a clear winner (in both places) as far sonics, as well as speed and energy transmission. (Flywheel to platter bond...)

I just wondered, if any of you can suggest any tensioning figure regarding this material (I am using 10-13% stretch). The problem is that the 3 things are far apart one from the other and there is some violin string effect. On the other hand, I wouldn't go too far with stretching, to keep the rubber cord from not permanently deformed...

Also if anybody knows any real strong glue for cord ends connection... and how about using it because at the connection area, due to the glue, the diameter gets a little larger and I don't like that ... and I cannot manage my fingers to have the 2 ends glued and perfectly aligned at the same time...

Regards
 
#23
Hi,

As far as the drive type is concerned, it seems that the 1.5mm OD rubber O' ring cord is a clear winner (in both places) as far sonics, as well as speed and energy transmission. (Flywheel to platter bond...)
Click to expand...

Well, well....guess I did something right after all....
The technical reasonigns are in the archive here....

Way to go and merry X-mass,

If you need to pick my brain, do a google on Nothingham Analogue, we're engineering soulmates...

Cheers,😉
 
#24
Re: Rubber O' ring belt a clear winner?

skaloumbakas said:

Also if anybody knows any real strong glue for cord ends connection...
Click to expand...

I suppose you may find a manufacturer to make you silicone rubber O-ring of desired dimentions in Greece. I ordered once a ring seal of 350 mm diameter and rather complicated crossection for one project (I'm in jet-engine engineering) from the local Israel manufacturer not for huge amount of money. You pay 95% for casting form and than you can order 20-50 pieces within same sum.
 
#27
Very surprised indeed...

Hi,

I am very surprised, I found in a thread (http://www.diyaudio.com/forums/showthread.php?s=&threadid=4578), dice45 to write about the Verdier platter:
Magnetic platter bearing: used by the Platine Verdier. If the Verdier platter is slowly turned by hand, height variations of the platter surface become observable. Goodbye stable VTA. Goodbye constant force situation for the platter bearing. And the platter has to be very high in order to minimize bearing influence on MC cartridges. I am not happy with that....
Click to expand...
and in the second page of the same thread:
Magnetic bearing: go and watch a Platine Verdier (without axial ball bearing of course), or better, have a linear dial gauge measuring the height variations while the motor drives the platter. A friend of mine did so and then he reported he wanted to find out whether height variations could be caused by the varying magnetic field of the ring magnets.
He told me, he had the impression of a mild form of cogging. From that day, i stopped to take magnetic bearing into consideration.
Click to expand...

As I mention in my flywheel project report (magnetic field section), I certainly didn't have any of this experience with my aas gabriel platter and this also holds true for my magnetically levitated flywheel, as well as with the magnetically levitated platter of TL Acoustics turntable design.

They all rotate stable, (without even the slightest vertical vibration!!!!) and dead quietly, exhibiting no rumble what so ever, far below any other bearing conception available and CERTAINLY NO COGGING!!!

I am very surprised indeed!!!!
 
#28
Hi,

Magnetic bearing: go and watch a Platine Verdier (without axial ball bearing of course),
Click to expand...

Without axial bearing are the key words: too much magnetic lift.

Anyway, I think this applies to the models described way before actual production.

The "Platine Verdier" was part of a series of articles in the French audiomag "L'Audiophile" where the idea originally was to give sufficient lift of the platter so it floated without making contact with the bottom of the bearing.

Not such a good idea as it turned out...For the same reasons the mercury floated platter by an another frenchman was flawed BTW.

Cheers, 😉
 
#30
Hello all,

Height variations on a magnetic suspended platter are due to false alignment of the repeling magnets. If the two magnets are not PERFECTLY centered, the magnetic field between them will not be constant resulting in height variations during platter rotation. Horror!:bigeyes:

K


MIN FONAZEIS XRHSTO, ERXETAI, EINAI STO DROMO!
 
#31
Hello all,

Height variations on a magnetic suspended platter are due to false alignment of the repeling magnets. If the two magnets are not PERFECTLY centered, the magnetic field between them will not be constant resulting in height variations during platter rotation. Horror!:bigeyes:

K


MIN FONAZEIS XRHSTO, ERXETAI, EINAI STO DROMO!
 
#32
Hello all,

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).
Click to expand...



"Traditional" ball bearings are ROTATIONAL pinpoint contacts with friction generating noise and we should not think of them like audiophile spikes. Ball bearings may provide perfect path for vibrations to be sunken by downlaid components, but are also the perfect path for outside generated vibrations to "hit" the cartridge's stylus.


K
 
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