conical versus ellipticals

[Ldg]

Decided to post my calcs on temp of stylus and vinyl in parts.

This is part 1, how much heat is generated. Source of heat is friction between groove and stylus.

From yosh's recspecs page citing JVC and other figures:

F = b*VTF

F is total friction force
b is coefficient of friction, 0.22 - 0.55 range
VTF is vertical tracking force

For typical b=0.4 and VTF=1.5gf, F=0.6gf=0.006N

For typical stylus velocity = 33cm/s =0.33m/s (inc rotation)

In one second, heat Q=0.006N*.0.33m=0.002 joules

Heat flow from stylus/groove friction P =0.002 joules per second = 2mW

[Paladin]

lessee if I can get a "hit" on this one. What are the pros and cons of each. Wear and tear of the vinyl? Difference in sound? Snip…

I count 129 conical styluses with 0.6-mil tips at the Cartridge Database and surely more to be discovered in the future. Many elliptical ride higher at 0.7. Back then it was kind of a standard. So anyone wanting to find the Holy Grail, the virgin vinyl, would use a conical.

Some people recommend using conical when records are noisy but don’t say why. Conical tips reach below damage or noise. And the reverse- some say their elliptical styluses makes noisy records. Could it be because someone abused a 0.6 conical tip in grooves which automatically damages anything above? Again, the 0.7 elliptical would read higher in the groove.

Because of more pressure at a concentrated point, conical tips wear the vinyl faster. With a good system, it might take 100 plays or more before the wear is noticed. But the conical leaves so many areas fresh for other tips. I think you’ll tire of a record before the wear is noticed.

Alignments are not nearly as crucial with a conical tip.

An elliptical tip CAN (not WILL as people and marketing say) sound better at the end of a record much like a performance car can go faster then a sports car in hairpin turns. But the road was designed for the sports car or worse. A record is designed to use a conical tip and the elliptical tip gets very little use out of its potential.

Use a conical on 45’s or prepare to cut a new groove.

Concial tips are used on cheap cartridges so classic cartridges with conical tips but great sounding are lumped in the same category.

Conical tips are bargains because people don’t see them.

[Ldg]

Here's part 2 of my calcs on temperature of stylus and vinyl.

Conclusion from part 1 is that typical heat flow rate at stylus/vinyl contact is of the order of 2mW.

Part 2 is a discussion of physics of what happens to the heat generated at the contact area.

At the contact area, diamond and vinyl materials mesh and are essentially a composite material in the region where friction takes place, not necessarily very deep, but essentially one material. Heat is generated by making and tearing apart this composite material, as the stylus traverses the vinyl surface.

Diamond is an exceptionally good conductor of heat. It has a coefficient of thermal conduction in range 900-2000, one of the best materials around. Vinyl is a poor conductor of heat, coefficient of thermal conduction 0.4 - 0.8. This means that approx 99.95% of the heat generated in the contact region is conducted by the diamond, and the tiny remainder 0.05% is conducted by the vinyl.

Before addressing the math calulating contact region temperature in the next part, note that virtually all heat flow is conducted away from this region through the diamond. Whatever the temperaure of the contact region, some 2mW * 0.0005 = 1uW is conducted by the vinyl. This is a very small heat flow !

[Ldg]

Perhaps more of these scanning electron microscope studies from AES would shed more light on this matter.

At the molecular level under SEM there's bound to be some damage arising with each playing, but how deep does this extend ? Not far in real terms.......it's not all about temperature, it's about heat. Ever passed your finger through a candle flame ? ......bet your finger had some molecular damage too !

[rito25]

So conical better but higher wear.
Elliptical not as good but less wear.
That to me says go ellipitical.

[Ldg]

Here's part 3 of my calcs on temperature of stylus and vinyl.

Conclusion from part 1 is that typical heat flow rate at stylus/vinyl contact is of the order of 2mW. Conclusion of part 2 is that whatever the temperaure of the contact region, some 1uW is conducted into the vinyl, and this is effective heating power.

This is part 3 and looks at temperature rise of vinyl near the contact region.

Vinyl contact region continuously changes as record moves.

Assume contact region has a surface radius of 3um, stylus/vinyl velocity = 0.33m/s.

In one second, area swept by contact region A = 3um * 0.33*10E+6 um = 10E+6 um^2
From part 2, heat flow rate into vinyl from contact region P = 1uW
then heat flux into vinyl groove wall Y = P/A = 1uW/10E+6 um^2 = 10E-12 W per um
1um^2 = 10E-12 m^2
then Y = 1 W per square meter

For vinyl groove skin depth of 0.1um, volume swept by contact region in one second V

V= A * 0.1um = 10E+6 um^2 * 0.1 um = 10E+5 um^3
1 um^3 = 10E-18 m^3
V = 10E-13 m^3
Specific gravity of vinyl is close to 1 g/cm^3 = 10E6 g/m^3
Weight of vinyl occupied by volume W = V * 10E6 g/m^3
W = 10E-7 g = 0.1ug

In one second, heat flow = 1 uJ
Specific heat of vinyl is close to 1J/gK

Then average temperature rise T of vinyl groove wall skin to thickness of 0.1um

T = 1 uJ / 0.1ug = 10 deg K (celsius)

Obviously, convenient typical values were chosen to make the math plain, but these choices seem reasonable. Point is, there is not significant heating of the vinyl groove wall skin, not enough to melt or deform.

[Ldg]

The contention is that it is only on the surface of the groove, where the stylus contacts, that the vinyl melts for an instant, then re-forms. Apparently this phenomena was OBSERVED by Mr Alexandrovich. The tremendous pressure might have more to do with it than theoretical temperature calculations.

ld,
I noticed that your formula for friction seems inadequate. Although 1.5g VTF is reasonable, the actual force is dramatically higher due to the size of the contact area. Was this taken into consideration?

No dispute that this phenomenum happens, in fact it's a normal part of contact physics. Surfaces mesh under pressure, the composite can be low friction, but it happens over very short distances at these pressures, orders of molecules. Not unusual to see much larger contact pressures elsewhere.

Yes, I've fully taken into account the difference between VTF the force (g) that brings about the pressure (g/um^2). Force and pressure are different entities, of course. It was yosh's JVC friction coefficient that opened the door to calculating heat generated by friction. This coefficient is simply validated by observation of skate force.

[analogaudio]

Paladin wrote

"A record is designed to use a conical tip and the elliptical tip gets very little use out of its potential. "

This is not true from the disc mastering viewpoint, the master groove is cut by a sapphire the shape of a chisel and if played back using the same stylus would be free from some types of tracking distortion. The use of a conical playback tip stylus was an economy measure and not because it did the job right. The elliptical playback stylus design was introduced because conical does not get the job done right. Elliptical is not perfect but introduces less tracking distortions than than conical.

Ted

[Paladin]

I didn’t know that albums were not designed for conical tips.

[Thomas_A]

Thanks Luckdog for the calculations. There are now two calculations showing that temperature rise in vinyl is small.

[Thomas_A]

""Role of Scanning Electron Microscope in Disc Recording." George Alexandrovich. AES Preprint 1274, 58th Convention.
Among other subjects we investigated was the method of playing records wet. By applying a thin film of water as the record was rotating and playing the groove with an ordinary stylus, it produced unexpected increase in vinyl deterioration in the area where the stylus was touching the groove. Our SEM pictures unveiled extraordinary ripping of the vinyl surface which I can explain only by the fact that the vinyl is not allowed to liquify momentarily under the pressure of a fast moving stylus because of the cooling action of water in the groove. This phenomenon, I believe, is identical to ice skating where one does not skate on ice but actually on a film of water which comes from the ice being momentarily melted under the pressure of the thin metal blade. If ice is too cold, one cannot skate. Evidence of the fact that vinyl melts can be found in pictures taken of record grooves played at different temperatures. "

I do not know exactly what would happen when the record is played wet. Cooling may be one thing, but I am not sure how much that will affect. Another thing might be a weaker contact between stulys and groove because of liquid passing between the stylus and groove, effectively reducing the contact force and area and significantly reduce friction. The end result may a stylus that is forced to stay in the middle of the groove, not following the high-frequency modulations, leading to reduced HF noise but also, tearing of grooves when stylus is constantly bouncing off and on the modulations.

Compare car wheels that loose contact when going too fast on a wet road.

[missan]

Some months ago I did a DSC analysis of a piece from a Decca record.
I found the Glass Transition to be just below 70degC.
As vinyl is a amorphous thermoplastic I believe if this temp is reached there will be a plastic deformation of the vinyl that is permanent.

Following this thread I am totally convinced that the transition in the vinyl is taking place in a very thin layer and is of no importance regarding deformation. If there should be any resamblance with ice skating I believe that the temp above the record´s surface must be closer to Tg temp. The surface pressure when playing will not normally make the vinyl too stressed, it´s still well within the elastic area.
missan
Edit: better spelling

[rayr0683]

Hello All,

I know that the grooves reach temperatures of about 350 degrees farenheit, but never have noticed and sound degradation on any albums that I play, or have played on a consistant basis. I wonder if this is being taken too seriously. It is very important to clean the stylus after every played side of an lp, from accumulated, and caked on gunk, from the heat, and other debris within grooves. It gets baked onto the stylus. However, when reading the studies that have been done with LAST ARCHIVAL RECORD PRESERVATIVE, after a good cleaning with a vacuum record cleaning machine, and also cleaning, and possibly using LAST Stylus preservative, the records that were played many many times, I forget the exact number of times, showed virtually no wear. So, proper cleaning, and the use of LAST products can keep your vinyl as new as possible. I do this myself, and have never noticed any problems. I myself dont use a microscope, but the LAST studies did. Ray

Some months ago I did a DSC analysis of a piece from a Decca record.
I found the Glass Transition to be just below 70degC.
As vinyl is a amorphous thermoplastic I believe if this temp is reached there will be a plastic deformation of the vinyl that is permanent.

Following this thread I am totally convinced that the transition in the vinyl is taking place in a very thin layer and is of no importance regarding deformation. If there should be any resamblance with ice skating I believe that the temp above the record´s surface must be closer to Tg temp. The surface pressure when playing will not normally make the vinyl more stressed than it´s still well within the elastic area.
missan

[Ldg]

Some months ago I did a DSC analysis of a piece from a Decca record.
I found the Glass Transition to be just below 70degC.
As vinyl is a amorphous thermoplastic I believe if this temp is reached there will be a plastic deformation of the vinyl that is permanent.

Following this thread I am totally convinced that the transition in the vinyl is taking place in a very thin layer and is of no importance regarding deformation. If there should be any resamblance with ice skating I believe that the temp above the record´s surface must be closer to Tg temp. The surface pressure when playing will not normally make the vinyl too stressed, it´s still well within the elastic area.
missan
Edit: better spelling

I agree, Missan. Even allowing for 'worst case' friction coefficient, high VTF, slowest velocity and smallest contact radius, temperature rise in the first 100nm skin of groove wall is below 20 deg C, well below glass temp even at high ambients.

Interesting that factors VTF, friction co-efficient, and contact area radius (inversely) influence temp rise linearly, and there's not a clear advantage between spherical or eliptical. Line contact has an advantage if increased line height offsets increased friction coefficient, but it all seems small and not significant.

I know that the grooves reach temperatures of about 350 degrees farenheit, but never have noticed and sound degradation on any albums that I play, or have played on a consistant basis.

That's because of what Missan describes. There's not enough heat associated, doesn't even significantly heat or deform 100nm groove skin.