Effect of Stylus friction on LP

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Hans Polak

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Joined 2005
Mark Tillotson said:
Plastic deformation is really not melting, trust me! If you bend a piece of wire, plastic rod, whatever, permanently then it has yielded and deformed plastically, but it never melted in your hands! There is no "plastic state" involved, plastic deformation just means it deformed irreversibly without fracturing - nothing more, nothing less - this can happen really fast or so slow that the temperature rise of the material is vanishingly small - plastic deformation happens in solids in their normal state when the forces are high enough and there is a mechanism to allow it (if not, the material behaves elastically until fracturing).

To melt a material all the molecules in it gain enough energy to become free to move on their own thereafter without further mechanical energy input. This is random thermal energy. Its a very simple process conceptually.

For mechanical energy to melt a solid typically a high energy shock-wave is required, such as from an explosion-front or hypersonic impact. Or you can apply sufficient friction to impart enough thermal energy to the bulk material.

Plastic deformation involves mechanisms that mainly act over an layers/areas, i.e. only some of the molecules, typically layers that get to slide over each other, allowing the overall shape to change with only a fraction of the material involved directly - the majority is still in the elastic state.

Take a sheet of plastic and cut it with scissors or a knife - this is plastic deformation - but the cut edges show no evidence of melting.

After plastic deformation the material is still in a state of high internal stress, and when the external force is removed creep can lead to some recovery of the deformation, especially in polymers - melting simply removes mechanical stresses.

Most materials capable of plastic deformation will eventually fail on repeated deformation to show a characteristically grainy rough failure surface, indicative of the network of isolated grains within a network of sliding layers, clearly not indicative of liquid state!
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Mark,

Thx for your contribution.
I fully agree with you, that’s why I talked from the beginning about plastic state and rejected the melting used by many like Alexandrovich.
Also see the definition I used in posting #1.
However I changed my description recently to those who didn’t understand this subtle difference between plastic state and fluid state.
That was probably a bad idea. :ROFLMAO:

Hans
 
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Hans Polak

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Chris Hornbeck said:
Thanks for the excellent description of the classical explanation. Perhaps we could all agree that the question revolves around whether or not the above condition applies to playing vinyl records. Could the test revolve around how much and how fast stresses are relieved?

All good fortune,
Chris

ps: Makes me think about the development of armor piercing projectiles for penetrating tanks and APCs and such. The modern approach is somewhat counter-intuitive.
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Hi Chris,

I can only keep pointing to the Bastiaans paper with his excellent work on calculating and measuring in life the recoverable elastic and non recoverable plastic state. The latter resuslting in permanent deformation.

Send me a PM when you want the full PDF

Hans
 
Chris Hornbeck

Chris Hornbeck

Member
Joined 2011
Thanks, I do have the Bastiaans of 10/1967, probably from your earlier paper. He's careful to mention unpredicted non-linearities in observed curves, for example his Fig. 2, and is also careful about applying "linear" scholastic models to an indifferent real world. He even hints at longer-time (more than immediate cooling time) effects. The things that interest us here are just at the edge of knowable, because our models are just at the edge of believable.

Much thanks, as always, and please keep it up,
Chris
 
Hiten

Hiten

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Joined 2010
Would a repeated play of full record (lets say 50 times) and then putting stylus tip immediately on precision digital thermometer work ?
my uneducated guess is stylus material absorbs most of heat and rapidly cools down. And moving vinyl record surface doesnt stay as long to get heat energy transfered to itself (as said earlier 'like quickly moving finger across lit candle')
 
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StevenCrook

StevenCrook

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Hans Polak said:
Since tests proving that LAST preservative manages to reduce IMD by a claimed 10dB are not available
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My big problem with LAST starts with the method of application. A few drops are applied to a microfibre cloth and then the cloth is wiped over the surface of the LP. How does the fluid can get to the parts of the groove that're in contact with the stylus? I could, perhaps, imagine that given enough time it would slowly migrate to cover the entire record surface. But, well, sceptical.

Hans, good luck with your tests, and thanks for taking the time to try it at all.
 
Ixnay

Ixnay

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Joined 2020
Hmm. The LAST record preservative that I bought is in a brown bottle with an eye dropper. Its consistency reminds of an alcohol based fluid. When applying to a record, it evaporates instantly, faster than alcohol. I load up the yellow short bristled brush applicator and hope to get around the record in time for the full surface to be covered.
 
StevenCrook

StevenCrook

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@ejp OK, applicator, but the instructions describe it as 'velvet' so I think my point remains, I don't see how the fluid gets into the groove to the stylus contact area. Particularly if it's the consistency of molasses. If it's as Ixnay describes the alcohol would act as a surfactant and allow it to spread, but then you've got to be quick before the alcohol evaporates. I'm old enough to remember Permastat, so cautious...
 
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kimon

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I just noticed this thread but I don't have the time read all the posts. I recalled an interview of Mitchell ("Mitch") A. Cotter to a greek magazine in the early '80s, that really impressed me.
Cotter stated that at the contact point of stylus and vinyl pressure is so high that allows to the stylus tip to penetrate the surface layer of the vinyl disc (around 3800 Angstrem- if my memory serves me well) and in fact to read the layer underneath. He considered this beneficial for S/N, because the cutting procedure in reality is ripping the material of the disc and, if the tip was sliding on the surface (as classic physics says), noise would be terrible.
He believed that stylus wear and disc wear was the result of supersonic resonance of the needle. An effective damping method was the increase of the tracking force. He said that he usually played his discs with a 3-4 grams tracking force.
 
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ejp

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dadaelectronics.com.au
Well molasses is putting it a bit strong but it has some viscosity. The real point is the rotating application. Not just a wipe. You are basically claiming, from incorrect premises and a position of no experience with the product, that it doesn’t work. My experience is otherwise, and specifically I don’t see anything about the application process, having done it many times, that would prevent it from reaching everywhere.
 
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Ixnay

Ixnay

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Joined 2020
I am fortunate to have a manual record holder with a handle that allows me to manually clean records without having to touch them. The point here is that I can also apply LAST to the record using the supplied applicator after cleaning in a way that I can slowly rotate the vinyl as the applicator sweeps with the grooves on the surface. Even then, I must watch closely, just how much product is being dispersed onto the vinyl surface. It can take more than one sweep to get the entire surface wet, but of course, not too wet. Once done, I don't repeat the process as I do not play albums 100 times and probably have access to the music in other ways.
As far as viscosity, I would compare it to alcohol, and sure enough it evaporates as quickly if not more so.
 
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Hans Polak

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Joined 2005
I have revised posting #1, because the coefficient of friction that I assumed to be 0.1, turned out to be 0.3 according to a paper from Robert P. Pardee that Bill Shurvinton made me aware of.
I also added some attention to mis-tracking, where the stylus is losing contact with the groove possibly causing permanent damage when landing back into the groove because of the huge acceleration force.
An image showing this damage is also added to #1.

Hans
 
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Mark Tillotson

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Joined 2018
lcsaszar said:
Is there any high resulution infrared camera/microscope that can measure the stylus tip temperature?
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The problem is sensitivity - a very small area emits very little IR radiation.
Hiten said:
Would a repeated play of full record (lets say 50 times) and then putting stylus tip immediately on precision digital thermometer work ?
my uneducated guess is stylus material absorbs most of heat and rapidly cools down.
Click to expand...
Yes, very rapidly for something that small. The diffusion equation relates rate of change to be inverse-square of dimensions, so half the size is 4 times more rapid.

I reckon a mathematical model is the best approach - after all we use it for heat sinks, engines, the interior of the sun, all very successfully given enough care in the design of the model. I'm sure someone's done this sometime...
 
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gpapag

gpapag

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lcsaszar said:
Is there any high resulution infrared camera/microscope that can measure the stylus tip temperature?
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With red dot the essential specs to look for.
Red underlined (more than) adequate values.
This is from a $30k unit.
George
 

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