Inverted Bearing’s ...OIL BATH

Re: Inverted Bearing’s ...OIL BATH

Postby Drew769 » Wed Jan 15, 2020 2:44 pm

Meanwhile in NJ, my ceramic bearing has around 50 hours on it and its performing well. No perceivable noise. I had to pop the platter off to move some things around on the weekend and the bearing looks great so far, and there seems to be no reduction of lube (no new lube needed at this time).
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Re: Inverted Bearing’s ...OIL BATH

Postby Golear » Wed Jan 15, 2020 3:35 pm

I think this will truly be my last post, too. Thanks for the clarification, Votan.

This is what I'm getting at:

The seem to be 5 points of contact between the top and bottom surface. That's where all the action will be. A film of lube will adhere against the two surfaces. What is critical is that the oil/paste form a strong bond with the materials of the bearing (a few molecules thick). And the molecules in the lube are also designed to slide past each other.

There's nothing fundamentally wrong with a paste and nothing fundamental to the bath that will ensure success. You'll just end up using two distinct types of lube. What is important is to find a lube that will adhere to the surface. And a paste lube can do that.

The oil bath can, indeed, work, of course. But personally, I'd investigate air bearings. I had no idea that one can use graphite! That will address the major $ in an air bearing - drilling tiny holes with a laser and ensuring equal pressure out of all the holes.
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Re: Inverted Bearing’s ...OIL BATH

Postby Brf » Wed Jan 15, 2020 4:28 pm

Golear, you got me curious, what are the 5 points of contact?

I count 2 - thrust plate and ball, and platter bushing and bearing shaft.
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Re: Inverted Bearing’s ...OIL BATH

Postby Votan » Wed Jan 15, 2020 6:21 pm

I guess he means the 5 micro-asperities which are the total points in which are in touch the two frictional surfaces in my image on my last post!!!
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Re: Inverted Bearing’s ...OIL BATH

Postby madrac » Wed Jan 15, 2020 8:07 pm

Votan

I like your idea of an inverted oil bath (and replaceable bearing design as well), but obviously requires proper design/engineering as I'm sure you agree as you are continuing to refine this idea.

With 30+ years in the lubricant and additive industry, I do want to make a few comments about your recent post with the surfaces diagram.

The picture / diagram you posted showing the surfaces under lubrication looks to be somewhere between boundary (metal to metal contact) and mixed lubrication (some metal-to-metal contact). In either case, the former is highest wear, the latter some wear...assuming oil alone (no additives). What one needs to achieve is hydrodynamic lubrication, which is where the oil film/flow completely separates the surface. Without sufficient flow and/or pressure (and the correct viscosity for the clearance) to overcome forces from loading, the surfaces will never separate enough to prevent metal to metal contact. If the force/load from the platter on the bearing is greater than atmospheric/hydrostatic pressure, it's highly unlikely the oil will get pushed across the entire surface - it'd would never get past the point where two asperities meet (kind of like a dam). I would expect the oil in the bath would get pushed out after the initial fill when the platter is reinstalled (unless, perhaps, an extremely viscous oil was used). As you stated, there is no such thing as a perfectly smooth surface without any asperities that I am aware of. A molecular layer of plain oil is insufficient to prevent wear.

In the case of modern oils (at least for engines, transmissions, and differentials), these all contain a selection of chemicals (additives). For engine oils, the primary antiwear additive is zinc dithiophosphate (ZDDP). This chemical forms a protective layer on the metal surfaces, which acts as a sacrificial film when in boundary or mixed regimes, and replenishes as the engine operates. Kind of like painting metal or anodizing aluminum. Gear oils typically have sulfur-phosphorus compounds which behave similar to ZDDP. I don't know a lot about greases, but they likely contain additives (like PTFE, as well as the soap complex used as a thickener). Grease is typically an oil (same as in a motor oil) of a certain viscosity (greases, like motor oils, come in a range of viscosities for different applications) with a thickener which keeps it in place. I believe the staying power is indicated by the drop point. This is what keeps the grease in place between the surfaces it is to lubricate. Anyways, oil / thickened grease would also fill those peaks/valleys although likely not replenished as no flow/way to force fresh grease into the contact zone (aside from manually relubing), so it is a possible solution. Many bearings (eg wheel bearings in your car) are lubricated with grease (and likely similar contact zones as the VPI inverted bearing/thrust plate) and operate for thousands and thousands of hours/miles without failure or being relubricated. So, is grease the best solution for the VPI application -- maybe / maybe not. Maybe there are other causes for the premature wear some are showing -- wrong grease, low quality grease, table not completely level, assembly, bearing quality, etc. Maybe the inverted oil bath with the right design to separate the surface is the better solution (but what is the cost to implement).

FYI, Grease, like motor oil, undergoes a number of tests to ensure it meets the indicated performance. Lubricant testing can be extremely costly -- for instance, a typical API GF5 oil which one would use in their car in North America, undergoes about USD300,000 worth of testing, assuming first time passes. 4-6 times that for a CK4 oil for HD diesel engines. I believe you live in Greece (beautiful country by the way) so you'd likely use an ACEA oil, usually with one or more European OEM claims...here, your looking at a million plus depending on the claims.
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Re: Inverted Bearing’s ...OIL BATH

Postby Waxxy » Thu Jan 16, 2020 5:38 pm

Votan wrote:
Golear wrote:This zone is charged by the whole weight of the platter with its accessories. In molecular level, the image that shows up (in magnification) the created frictional contact zone is as follows:

Frictinal contact zone in Oil Bath.jpg

From the above image it is obvious that contrary to what is speculated by Golear and Waxxy, the "perfectly" smooth frictional surfaces, not only do not displace the lubricant oil from the contact zone, but instead, when it is stationary (platter not spinning), retain it stored in this critical zone!
Why? As it seems in the picture above (and also has been explained), throughout the frictional zone there are scattered pits and fissures with micro-asperities which are what causes friction when the platter spins. In fact, they all hydraulically communicate with each other, since frictional surfaces are in contact only just at micro-asperities (see pictures above). Add to that the capillary phenomenon as well.
So, once the rotation of the platter begins, the oil is drifting and constantly lubricates the continuously alternating contact points of micro-asperities.


Votan, (edit: I mistakenly addressed this to golear)

The image you included depicts two mated flat surfaces, whereas the VPI bearing uses a sphere against a flat surface. A sphere (without deflection) will have the smallest amount of contact possible, smaller than the imperfections on the sphere. Even with all the imperfections of a man-made sphere, the contact point would not allow "scattered pits and fissures" to come into contact with a thrust plate, unless the thrust plate material was to deflect significantly...which in the case of the VPI bearing / thrust plate, it does. And so... The soft PEEK material deflection would also fill the any pits and fissures on the stainless steel ball.

If the sphere material also deflects, it would certainly flatten and fill the pits and points. I don't imagine there is much sphere deflection though, in the case of stainless steel against PEEK.

The two surfaces are in contact to a far greater extent than the "continuously alternating contact points of micro-asperities" you suggest.

On a side note, my nearly 40 year old Kenwood turntable used a bearing made with a blunt / flat ended shaft against a Teflon (or similar material) thrust pad. It was dead silent.
Last edited by Waxxy on Thu Jan 16, 2020 6:21 pm, edited 1 time in total.
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Re: Inverted Bearing’s ...OIL BATH

Postby Votan » Thu Jan 16, 2020 6:17 pm

madrac wrote: Votan
I like your idea of an inverted oil bath (and replaceable bearing design as well), but obviously requires proper design/engineering as I'm sure you agree as you are continuing to refine this idea.

Thanks! I agree.
madrac wrote:With 30+ years in the lubricant and additive industry, I do want to make a few comments about your recent post with the surfaces diagram.

I am sincerely pleased that finally some documented views are being presented (with the exception Brf’s interventions here so far), for discussion and/or disagreement-confrontation, by a person who is very adept at the subject. My engineering studies contained courses from Tribology as well, but I confess I don't have your 30 + years experience!
madrac wrote: . A molecular layer of plain oil is insufficient to prevent wear.
In the case of modern oils (at least for engines, transmissions, and differentials), these all contain a selection of chemicals (additives). For engine oils, the primary antiwear additive is zinc dithiophosphate (ZDDP). This chemical forms a protective layer on the metal surfaces, which acts as a sacrificial film when in boundary or mixed regimes, and replenishes as the engine operates. Kind of like painting metal or anodizing aluminum. I don't know a lot about greases, but they likely contain additives (like PTFE, as well as the soap complex used as a thickener).

It goes without saying that both the proposed idea here, as well as the audiophiles users of lubricant oil in their TTs, are supposed to use the best possible oil, usually Mobil 1, which I believe contains the appropriate additives.
In any case, with your experience, why don't you recommend here the most suitable oil/grease for this very case?
madrac wrote: The picture / diagram you posted showing the surfaces under lubrication looks to be somewhere between boundary (metal to metal contact) and mixed lubrication (some metal-to-metal contact). In either case, the former is highest wear, the latter some wear...assuming oil alone (no additives). What one needs to achieve is hydrodynamic lubrication, which is where the oil film/flow completely separates the surface.
Maybe the inverted oil bath with the right design to separate the surface is the better solution (but what is the cost to implement). .

Here is an image that represents comparatively the cases of lubrication you describe according to the charging of the bearing and the applied (or not) overpressure onto the frictional zone:
Top Image: No lubrication at all
Second from the top: Hydrodynamic lubrication
Third from the top: Mixed lubrication
Forth from the top: Boundary lubrication (our case)
Types of Lubrication.jpg
Types of Lubrication.jpg (38.17 KiB) Viewed 983 times

You can see that in all cases (excluding the “No lubing at all”) provision is made for the use of additives
Hydrodynamic lubrication: In case of inverted bearing TTs, hypothetically this could be done almost like in “Air Bearing” TTs, namely by applying very high hydrodynamic oil pressure inside the bearing chamber could be created an up-thrust to the platter overcoming all of its weight B, or alternatively most of it , eliminating charging in the frictional contact zone, or at least, dramatically reducing it.
This could be achieved through the circulation of the oil through an external (to the TT) high pressure electric pump and a suitable oil pipe network, a part of which should be external, the rest of it should be inside the TT, passing through its inverted bearing shaft and discharging inside the bearing chamber..
This last solution seems ideal from the friction point of view, because of very low or zero platter’s weight to bearing, thus extremely low fiction (equals only to the viscosity friction of the fluid) .
But I do not know this technique to have applied to some TT in production. Probably, this is because of:
• Its very high cost (relevant to those of Air bearing TTs) , or/and
• Technical problems, such as the very complex oil pipe network with a noisy external high pressure pumps and
• A very noisy flow of oil into the bearing chamber, which dramatically should affect TT’s sonics.
But if that’s so, why not to go directly for an Air Bearing TT?
madrac wrote: Without sufficient flow and/or pressure (and the correct viscosity for the clearance) to overcome forces from loading, the surfaces will never separate enough to prevent metal to metal contact. ).

This paragraph of yours, as it is worded in the order of your text, assumes lubricant oil without additives. With this condition, I agree with your conclusions. But as above I stated the oil that will be used will be the best ever with the appropriate additives, with which the quality and efficiency of the lubrication is significantly improved, as in your declare in your statement above: "This Chemical (additives) forms a protective layer on the metal surfaces, which acts as a sacrificial film when in boundary or mixed regimes, and replenishes as the engine operates "
madrac wrote: If the force/load from the platter on the bearing is greater than atmospheric/hydrostatic pressure, it's highly unlikely the oil will get pushed across the entire surface - it would never get past the point where two asperities meet (kind of like a dam). I would expect the oil in the bath would get pushed out after the initial fill when the platter is reinstalled (unless, perhaps, an extremely viscous oil was used). As you stated, there is no such thing as a perfectly smooth surface without any asperities that I am aware of.

In this point I disagree with you!
As it has been mentioned in my previous post, in the lubrication process of the proposed inverted bearing oil bath, first we put a few drops of oil in its well to overlap the ball’s top (oil bath) and then we place the platter, the thrust pad of which creates the contact zone with the immersed ball bearing. From the above image it is obvious that contrary to what you speculate, the "perfectly" smooth frictional surfaces, not only do not displace the lubricant oil from the contact zone, but instead, when it is stationary (platter not spinning), retain it stored in this critical zone!
As well, the point where two micro-asperities meet, is exactly as you describe it: A POINT! But NOT a dam! Even if a micro-asperity is pointing to a larger more flat micro-area, once again it's a POINT. Inside the frictional contact zone there are too many such "points" but they do not cut off the communicational hydraulic continuity of all contact zone areas. It's almost like the next picture that represents a famous cavern of my Country.
Caves with aspirities.jpg
Caves with aspirities.jpg (50.19 KiB) Viewed 983 times

Micro-asperities contact points are not elongated walls that create isolated cells that do not communicate hydraulically with the external environment of oil bath.
But even if somewhere some isolated cells occur, each cell will be full of trapped oil, as the platter is placed and its thrust pad will be pressed onto the ball bearing. As also with the platter's infinitesvery first move to rotate, any pre-existing isolation at some point will cease to exist, as it will change any pre-created dams. As the continuous alteration of the surface relief due to rotation, it allows only any momentary isolated cells.
madrac wrote: Anyways, oil / thickened grease would also fill those peaks/valleys although likely not replenished as no flow/way to force fresh grease into the contact zone (aside from manually relubing), so it is a possible solution.

This (no replenished) however, is an important and critical disadvantage of grease versus lubricating oil.
With grease, which remains stuck in frictional contact zone, it overheats due friction and after a while it chemically decomposed, losing its lubricating properties. With grease no recirculation potential, nor for replenishment of the displaced one due to centrifugation, so nor cooling of overheated frictional zone.
madrac wrote: Many bearings (eg wheel bearings in your car) are lubricated with grease (and likely similar contact zones as the VPI inverted bearing/thrust plate) and operate for thousands and thousands of hours/miles without failure or being relubricated. So, is grease the best solution for the VPI application -- maybe / maybe not. Maybe there are other causes for the premature wear some are showing -- wrong grease, low quality grease, table not completely level, assembly, bearing quality, etc.

Most, if not all bearings on a car are of the type "rotating bearings" for horizontal axes, which operate with the principles of rolling friction that is clearly much less than the sliding friction of TT inverted Bearing.
axles bearing.jpg
axles bearing.jpg (7.77 KiB) Viewed 983 times

Also in the rotating bearings, the points of rolling friction of the balls constantly alternate as they are rolled, while many of those bearings are of closed type, so the grease remains trapped, constantly lubricating, cooling and cooled and not displaced from the lubrication points. Thus the much lower wear of rolling bearings.
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Re: Inverted Bearing’s ...OIL BATH

Postby Votan » Thu Jan 16, 2020 6:50 pm

Waxxy wrote:The image you included depicts two mated flat surfaces, whereas the VPI bearing uses a sphere against a flat surface. A sphere (without deflection) will have the smallest amount of contact possible, smaller than the imperfections on the sphere. Even with all the imperfections of a man-made sphere, the contact point would not allow "scattered pits and fissures" to come into contact with a thrust plate, unless the thrust plate material was to deflect significantly...which in the case of the VPI bearing / thrust plate, it does. And so... The soft PEEK material deflection would also fill the any pits and fissures on the stainless steel ball.

If the sphere material also deflects, it would certainly flatten and fill the pits and points. I don't imagine there is much sphere deflection though, in the case of stainless steel against PEEK.

The two surfaces are in contact to a far greater extent than the "continuously alternating contact points of micro-asperities" you suggest.

On a side note, my nearly 40 year old Kenwood turntable used a bearing made with a blunt / flat ended shaft against a Teflon (or similar material) thrust pad. It was dead silent.

Waxy, in your older post in this topic you had again claimed that "The weight of any platter on top of such a bearing would be focused down to a point where The lubrication would be" squeezed out "and no oil could ever find its way back between τhe two mated surfaces ... It's impossible.
The oil/grease in a turntable bearing is strictly used to fill the gap between the shaft and sleeve and lubricate that portion of the bearing from side load friction. "

On that point I asked you: "If so, would you dare to spin your TT for some tens or hundreds of hours (with intermediate stops of course) completely dry without a trace of lube on its ball bearing?”
But I did not get an answer so far!
The issues you pose also apply to inverted bearingσ with grease, but I don't see you were bothered so far about them.
In any case, if you have anything better to suggest, I'd be happy to discuss it.
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Re: Inverted Bearing’s ...OIL BATH

Postby Waxxy » Thu Jan 16, 2020 10:25 pm

Votan wrote:
Waxxy wrote:The image you included depicts two mated flat surfaces, whereas the VPI bearing uses a sphere against a flat surface. A sphere (without deflection) will have the smallest amount of contact possible, smaller than the imperfections on the sphere. Even with all the imperfections of a man-made sphere, the contact point would not allow "scattered pits and fissures" to come into contact with a thrust plate, unless the thrust plate material was to deflect significantly...which in the case of the VPI bearing / thrust plate, it does. And so... The soft PEEK material deflection would also fill the any pits and fissures on the stainless steel ball.

If the sphere material also deflects, it would certainly flatten and fill the pits and points. I don't imagine there is much sphere deflection though, in the case of stainless steel against PEEK.

The two surfaces are in contact to a far greater extent than the "continuously alternating contact points of micro-asperities" you suggest.

On a side note, my nearly 40 year old Kenwood turntable used a bearing made with a blunt / flat ended shaft against a Teflon (or similar material) thrust pad. It was dead silent.

Waxy, in your older post in this topic you had again claimed that "The weight of any platter on top of such a bearing would be focused down to a point where The lubrication would be" squeezed out "and no oil could ever find its way back between τhe two mated surfaces ... It's impossible.
The oil/grease in a turntable bearing is strictly used to fill the gap between the shaft and sleeve and lubricate that portion of the bearing from side load friction. "

On that point I asked you: "If so, would you dare to spin your TT for some tens or hundreds of hours (with intermediate stops of course) completely dry without a trace of lube on its ball bearing?”
But I did not get an answer so far!
The issues you pose also apply to inverted bearingσ with grease, but I don't see you were bothered so far about them.
In any case, if you have anything better to suggest, I'd be happy to discuss it.


Votan,

Yes I would have no problem spinning my turntable without lube on the ball because the peek thrust pad is sufficient to minimize friction and noise. Just as I quoted Harry, and you mistakenly assumed he had produced a special bearing...it was stock, the soft thrust pad is sufficient. In fact, I'm sure most of the complaints in this forum come from folks who are visibly observing scouring on the bearing, but could not hear any negative issues beforehand...Vienna being a perfect example. Raving about the Sound of his turntable with the Votan tweak, yet a few days later claiming his turntable is unusable because of bearing damage.

And I have already mentioned that I think a soft thrust pad is the way to go...two ultra firm surfaces (ceramic, gemstone) will have more friction potential that cannot be solved with any lubricant.

Now perhaps you can respond to my statement...that the soft surface of the PEEK material would fill the gaps between the surfaces and the idea of "continuously alternating contact points of micro-asperities" is ludicrous. Even if both surfaces were ultra hard ceramic, they would quickly be polished down during weighted rotation leaving a very polished and smooth surface.
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Re: Inverted Bearing’s ...OIL BATH

Postby Mr_Putty » Fri Jan 17, 2020 3:29 am

Not intending to disrupt the discussion, but some may want to look at “researchgate.net”. There are lots of technical papers about friction and bearing lubrication. Some explore graphene oxide, while others talk about glass fibers imbedded in a plastic bearing surface that is in contact with metal. There is mention that when a slick plastic shows a circular scoring wear pattern it is because there is formation of new (undesirable) compounds of the plastic. My brief reading conclusion (in the papers) is the importance of the proper mix of materials and lubricant relative to the force exerted on the materials in the bearing. The most interesting idea was that strands of graphene (not oil or additives) had been attached to one of the bearing surfaces. And, a bit like a shag carpet, the strands kept the bearing surfaces apart. :arrow: :arrow:
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