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Old 4th December 2010, 07:28 PM   #231
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No point calculating you need to build in adjustability, either in the number of magnets you can use or the distance they can be spaced from the opposing magnet. you'll never get the ride height and damping correct by estimating or calculating, it has to be tuned by eye and ear.
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Old 8th December 2010, 08:25 AM   #232
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Quote:
Originally Posted by Vinyl-Addict View Post
I just completed my magnetic bearing using opposing ring magnets. It took me awhile to find the right strength and magnets that would fit my upper & lower bearing housings. I built my turntable with my own inverted bearing design that worked very well to support the 36 pound platter. I initially used a tungsten carbide thrust plate but I always wanted to relieve the immense force it had to undertake to support the high mass platter. Anyway, that was over a year ago and after searching on & off I finally found a pair of magnets that fit both my criteria.
After building a test fixture and measuring clearance, I was satisfied that machining the pockets and bonding the magnets would be the final test to see if the magnets would perform as I hoped they would.
I initially assembled the lower & upper bearing housings which was a challenge because of the 100 pounds of opposing force generated by the magnets. I had to machine a Delrin sleeve to extend the length of the inverted bearing shaft, after that I assembled both housings and placed the platter on top.
I did this on a granite surface plate so I could place a dial indicator on the platter to measure deviation. The total measured deviation from perfection was 0.1mm, hardly anything to be concerned with.
I then put it to the true test and actually played record after record. What an improvement! Ultra quiet and smooth as silk, well worth all the effort. Below is an image of the lower bearing housing that shows one of the ring magnets bonded to the lower housing. The magnet is nickel plated. Another image shows the complete turntable.


Click the image to open in full size.

Click the image to open in full size.
Links are not available anymore.
Could you please reup plz?
Thanks in advance.
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Old 31st January 2011, 10:12 AM   #233
yaccbr is offline yaccbr  Brazil
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Ok, the center shaft on a magnetic bearing design is to solve the imposibility of a estable floating platter without any mechanical self-centering device...

But and this solution?

Click the image to open in full size.


Used on the "Mercure Turntable": Mercury Turntable


Could it be used instead?

(sorry for my poor english)
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Old 31st January 2011, 06:32 PM   #234
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That would never be stable, to be stable would require huge tension in the belt, and that= high side loading on the pulleys and that = noise.
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Old 1st October 2011, 10:54 AM   #235
dady is offline dady  Argentina
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HI Dear, some one year ago we interchange some ideas related to bearing magnetic suspension, i have a RX1500 micro seiki with aluminium platter and vacumm pump. Unluckely it's not with air suspension and for that reason i start to investigate, I could solution the problem and i made a new axle in stainless antimagnetic copying the orginal axle with so close tolerances, and i prolonged i to the botton for acoplate one 5cm neodymiun magnet and make a coup for the other one scrweed to the bearing original one, i rise the weight of the plater in 20kg and balanced it and the result was amazing, the turntable work very good. The engine now is a little stressed at the starting but once it turn, nothing can't stop it. If you want the pics and the plans, I did it with a machiner in Argentina, they are a close friends because i lived there for 47 years.
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Old 16th October 2011, 05:48 AM   #236
Leolo is offline Leolo  Canada
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A source of small, cheap neodymium magnets, with force charts: Rare Earth Neodymium Magnets: Build Your Custom Magnet Sets Here

80 2.5x7 cylindrical magnets would generate 94 kg of force and cost 20 CAD. Magnet strength diminishes as a square of the distance. But a turntable only needson the order of a 1-3 mm.
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Old 20th April 2012, 02:08 PM   #237
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hello I began this post after reading it because I had been experimenting with levitation tray on my turntable.
I had given up because it was difficult for me to find the right magnets and the experiment would become very expensive to test various types of magnets.
So, after reading this post, I would therefore like to revisit the issue.
The acrylic plate of my platinum weighs + / - 8.5 kg and is 80mm thick ...
the diameter of the bearing is 40mm at its base, so I had thought of two ring magnets D60mm xd 40mm x 5mm ep, one fixed (the base) and the other inserted into the tray so obtain a distance of 1mm between the two, I thought adjusting the insertion depth of the magnet to reach the plateau at the correct distance of 1mm.
The problem with this kind of dimension is not common in this type of magnet, and I do not know how to grade (too repulsive or too little, I only have 20mm of adjustment range in the acrylic shelf (depth of ebcastrement ..)
Or do the alternative "ynwoan" and make two hard pmma or other dimensions of the ring magnets that I search and add several small magnets inside the cylinder style D8mm 5mm ep?
But the problem lies: what rank and choose how many magnets?? I think eventually achieve the two rings and drill holes as much as possible, then insert the magnets if the repulsion is too strong, I removed to obtain the correct distance (1mm) and then I realized my rings Definitive Media ...
By cons if it is not strong enough problem because I can not play on the outside diameter, so the number of holes ...
Have you any idea?
(I attached some pictures of the plateau and the axis) ( sorry for my bad english...google translate)
Attached Images
File Type: jpg DSC00528.JPG (46.7 KB, 126 views)
File Type: jpg DSC00522.JPG (29.1 KB, 133 views)

Last edited by Sourdingue; 20th April 2012 at 02:10 PM. Reason: modif language
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Old 24th April 2012, 06:42 PM   #238
dady is offline dady  Argentina
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Some year ago I modify a Thorens with magnetic platter for avoid the rumble noise, I found a very annoying problem, the tonearm was influenced for the magnetic field and the whole work went to the garbich. The problem is there are no efficient measures to do that. Right now the solution became of make a prolongation of the axle further the space of the bush in the botton further the ball under the turntable. More magnetic power, more distance you have to take. I use anti-magnetic stainless steel and I have to make a gunmetal coup for put the magnet in the screwed in the botton part of the axle's bush , The magnets are two: one in the coup and one attached to the botton of the axle of 50mm diameter for 20mm of tall each. The gap between the magnets is close to 0,1mm with the weight of 24kg. I made a mold of plaster the inner part of the platter and then with this mold I constructed another to be able to put lead melted which finally was stuck within the plate. I had to reinforce the springs of the suspension system but the result was an amazing turntable.
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Old 19th November 2012, 09:14 AM   #239
dady is offline dady  Argentina
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This are the parts I assembled for modify the Micro Seiki RX1500 VG
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Old 19th November 2012, 09:20 AM   #240
dady is offline dady  Argentina
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Default The Magnetic platter

Quote:
Originally Posted by dady View Post
This are the parts I assembled for modify the Micro Seiki RX1500 VG
The cup behind the axle contain the 5cm neodym magnet and the other is possible to see in the axle. Is possible to see the original axle (steel) and the new one (nonmagnetic stainless steel)
Attached Images
File Type: jpg 2012-11-08 18.47.29.jpg (100.0 KB, 95 views)
File Type: jpg 2012-11-08 18.44.27.jpg (95.5 KB, 71 views)
File Type: jpg 2012-11-08 18.44.37.jpg (95.6 KB, 69 views)
File Type: jpg 2012-11-08 18.44.55.jpg (100.7 KB, 62 views)
File Type: jpg 2012-11-08 18.45.08.jpg (100.1 KB, 50 views)
File Type: jpg 2012-11-08 18.45.57.jpg (98.0 KB, 46 views)
File Type: jpg 2012-11-08 18.48.06.jpg (93.3 KB, 49 views)
File Type: jpg 2012-11-08 18.49.04.jpg (94.9 KB, 59 views)
File Type: jpg 2012-11-08 18.49.59.jpg (99.9 KB, 59 views)
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