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Old 5th April 2004, 02:38 PM   #1
MannyE is offline MannyE  United States
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Default Turntable "floating platter" attempts

Hi folks!

I' have been playing around with this idea for a few days now and I want to start trying out prototypes this weekend.

If anyone has already attempted this, I would be grateful for any feedback.

I want to attempt a "floating platter". My first ideas were to literally float it in a high viscosity fluid and spin it via magnets in a sub-platter. But I quickly realized it would be slammed into the bottom of the container by the magnets.

Repelling magnetic bearings are too much hassle, and I saw the very complicated setup of the French TT that uses mag-lev.

I may have to settle for a simple elimination of the belt and go with a magnetic sub-platter the couples to the main platter. At least that way I will be able to eliminate any transfer of motor noise.

If anyone has an idea on how to float the platter in liquid, I would be intrested in trying it out.
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Old 5th April 2004, 03:14 PM   #2
MannyE is offline MannyE  United States
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and yes, I did go through the big TT thread, but the oil bath TT designs all employed a bearing...which is what I want to eliminate.
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Old 5th April 2004, 05:05 PM   #3
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Hi Manny,

For several years I am thinking of an air-bearing table. A few nozzles at the surround will get it turning. I am thinking of an eddy-current brake to control the speed then. But it is still an idea

Cheers
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Old 5th April 2004, 07:42 PM   #4
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Hi Manny and Pjotr
Back in the 70´s i made a floating platter tt by using a belt driven subplatter formed as a circular tub. Filled this with Citroen vegetable hydraulic oil and put a lightweight aluminium/cork floating platter inside. The upper platter had radial fins dipping down into the oil which made it follow the stream so to speak. I had a hard time keeping it centered to avoid wow. My aim was to eliminate feedback which worked, but compared to tt´s with a realy rigid coupling between platter bearing and arm bearing the floating tt was lousy at picking up small detail and dynamics. It was fun thou. Dont use a floting platter tt if Yové got a cat!
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Old 5th April 2004, 08:02 PM   #5
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Quote:
Originally posted by ingvar ahlberg

... but compared to tt´s with a realy rigid coupling between platter bearing and arm bearing the floating tt was lousy at picking up small detail and dynamics. It was fun thou. [/B]
Hi Ingvar,

That is one of my main concerns. I am thinking of a really heavy platter made of marmor or a sandwich of 10mm steel plates with damping material in between (easier to machine). The air bearing is just for supporting the weight, it will still have a centre pin for centring the whole platter. I have seen combinations of air bearings together with a vacuum "bearing" that were really “stiff”.

Cheers
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Old 5th April 2004, 08:30 PM   #6
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Allright, sounds fun, i´ve been fiddling with the idea of a pneumatic circularmotion valve to drive the platter. Maybee combine the two? Problem with pneumatics is to get rid of noice from escape air.
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Old 5th April 2004, 09:33 PM   #7
MannyE is offline MannyE  United States
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The air bearing idea has been covered exstensively in the turntable mega-thread (31 pages and going!)

There is a lot of great reading in there. Even the air bearing has that fatal centering pin which will connect the platter to the outside world, so to speak.

However, I have been going over this for some time, and I really can'y see a way to keep it simple and at the same time completely eliminate any connection of the platter to anything but fluid...SO! Here's what I am thinking to do.

Build a "platter assembly" that consists of the platter in an oil bath with either the centering pin or the "ring" rudder and centering pin. (you can find these in the mega thread).

THEN... make the sub-platter motor assembly and use magnets to turn the platter! I think this will work and since the platter is supported, eliminate the wow and flutter problems from wave motion without having a physical bond to the motor.... I can get to work now!
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Old 6th April 2004, 11:31 AM   #8
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Hi all

I use a Well Tempered turntable and have been thinking about how
to use a heavy platter with the teflon-pad/silicon oil bearing of the Well Tempered.
Haven't red the turntable mega-thread, but probably will now.
Anyway, what if I use the teflon-pad bearing and support the platter with
an air bearing or magnetic ditto?

Just a thought, have to think more about this one

cheers
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Old 6th April 2004, 10:27 PM   #9
DeonC is offline DeonC  South Africa
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Default Re. air-bearing and centering

Hi Manny and Pjotr

I remember a TT that was designed to float on mercury. I added an addition to the design that added a iol bath around the mercury bath to keep mercury fumes in. That design had a proposition to use a belt around the circumference, but with four bearings placed at equidistant points around the platter. If the belt is wound around the bearings it only touches the platter at four points around the circumference. That was designed to centre the platter without the use of a centre spindle. That leads me to my idea.

How about this for an idea:
1. use an air-bearing to float the platter, but don't use a centre spindle at all
2. put the platter in a 'well', with air-bearing nozzles similar to that used to float the platter around the circumference of the inside of the 'well'. That way air-bearing will not just be below the platter in order to float it, but also around it to keep it centered.

You can take this idea further and add vanes in the side of the platter, and then use the side nozzles to drive it.

For a brake you can use something similar to what Technics used in their SP10. They simply put a metal ribbon around the platter. The ribbon was fastened to the side and had a tightening mechanism. When the platter needed to be stopped, the mechanism contracted tightening around the platter. It is a very simple mechanism. In the idea above you don't have a centre spindle\bearing, so that can't be damaged by a system like this either

I hope my explanations are clear. I can see the idea clearly in my head, but trying put it in words is not so easy. I will try to add an image (this is my first time) to try and explain the concept.

Ok, if the image loads, then you will see the platter in the 'well' with nozzles all around for the floating and centering. Please note that this is a very crude illustration, but it is only meant to try and better convey my idea.

Enjoy,
Deon
Attached Images
File Type: gif totally suspended platter.gif (2.6 KB, 1121 views)
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Old 6th April 2004, 10:42 PM   #10
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Hi,

Deon,

The floating platter idea has a major drawback; the energy can't get away except through the stylus mechanism of the cartridge.

That is, unfortunately, the last point of exit for any energy you'd want.

It's also one of the reasons this idea was dirched, the other being the poisonous nature of mercury.

BTW, airbearing TTs suffer from the same energy drain problem.
The only viable solution I can put forward is to still use a bearing but with only a small load on it as opposed to the full weight of the more classic approaches.

Cheers,
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