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One of my favourite websites is TribologyABC.com, source of many useful calculators and much help with the design of bearings. I recently bought the associated book "Advanced Engineering Design" and am steadily ploughing through it.On reading the section on frictional heating in a ball on surface contact I realised that the same calculation could be brought to bear on the chestnut regarding the heating effect of a diamond stylus on vinyl. The appropriate calculator is 5.5 on the website.
If we use appropriate values for the diamond / vinyl interface, making worst case assumptions where values are hard to determine, we can calculate a temperature rise for contact patch of the vinyl surface. The answer comes out to about 10oC. No, that's not a typo, that's 10 degrees celsius or 18 degrees Fahrenheit.
The 24 hour rule is dead. Don't start with the stuff about slow recovery after deformation, it's called stress creep and the recovery time is proportional to the creep strain which in turn is proportional to the stress duration, so the recovery period is of the same order of magnitude as the stress period.
For those who want to check my results, I used the following values:
Thermal conductivity diamond = 1000 W/mK.
Thermal conductivity PVC = 0.16 W/mK
Thermal diffusivity PVC = 1.2 x 10^-7 m^2/s
H (Hardness of interface) = 1 GPa (the hardness of the softer material dominates)
F = 15 N (1.5 g VTF)
V = 0.5 m/s
mu = 0.4 (a reasonable value for PVC/ diamond)
Assumed radius of contact patch = 70 um (deliberately large as the frictional coefficient of polymer materials increases as the contact pressure decreases, in contrast with classic solid bodies where the two are independent. This is why wide tyres work.)
By the way since we are working with a soft polymer Ar is roughly equal to An and it is easy to throw the calculator out of whack by giving values which would make Ar > An (which is impossible). AFAICS this does not affect the accuracy the model.
Mark Kelly
Follow Ups:
I had a hard time keeping milk from comong out my nose when I read somewhere on this forum that the tempurature generated by a stylus against the groove was 4oo plus degrees. I wan't even drinking milk at the time.
instead of the usual old hear-saying and nonsense.
Interesting analysis and I haven't studied it in much detail but it seems to assume perfect cooling of the stylus itself. Is that right? After all, a spot of vinyl is only in contact with the stylus for a very short period of time but the stylus is in contact with the vinyl for 20+ minutes and has to get rid of heat somehow. How hot does the stylus get and how fast? Can you offer a quantitative argument why this effect should be negligible?
The analysis presented models the contact as a sphere and includes the heat distribution within the sphere. It does not assume infinite conduction as that would give zero temperature rise.To accurately model the temperature rise in the contacting stylus we would need to know the thermal conductivity of the cantilever and especially the junction between the cantilever and the stylus. In the absence of better information I would defer to the measurements made by Van den Hul which gave about 40 - 140 oC rise in diamond temperature.
Caffienator has pointed out that I made a mistake in my calculation when I put 15N as the down force instead of 15mN.The change in the predicted result is quite interesting - it reduces the actual contact area by slightly more than it reduces the heat generated, so the hotspot temperature rise increases to 17oC and the average temperature rise decreases to less than 0.1oC.
My thanks to Caffienator for pointing out the error.
I'm putting my $$$ on VDH.
No Guru, No Method, No Teacher
As I pointed out below there is no conflict between this result and Van den Hul's measurements. The diamond gets reasonably hot, the vinyl doesn't.
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No Guru, No Method, No Teacher
Does this mean I no longer need to keep my acrylic platter in the freezer between plays?
No need to chill that platter any more - btw, I took mine out long ago to make room for the Gin. Seems to have done more to enhance listening enjoyment than most other tweaks...
Gin in the freezer? Hmmm... I've only done this with vodka when I intend to drink it neat with caviar, smoked salmon or oysters. It might make sense for a Martini straight up rather than water it down with ice in the shaker. I think I'll give it a try. This might be the best advice I've ever seen here!
Excellent results, but the "usual" rebuttal to that is that, of course, people have HEARD the temperature changes distorting the record, therefore the theoretical results are wrong. Which is a load of BS of course, but it does suggest that an empirical observation is needed to lay this to rest once and for all. I can provide two counterarguments to your analysis, but they're both sort of shaky.The first counterargument is that, as others have mentioned, the actual temperature of the stylus ought to take into account the very small size of the stylus. I would expect the "observed" thermal conductivity to be heavily influenced by the conductivity of the air and of the cantilever material. I do not posess the knowledge to numerically evaluate this though, I'm not a trained materials engineer, and I haven't done a heat transfer problem since college, so I could be blowing that out of my ass.
The second counterargument is that record degredation through repeated playback of records HAS been observed; all of the root causes have not been isolated yet, and temperature-related effects are among the suspects. I was just reading Audio Magazine's review of the Audio Technica LifeSaver the other day, and the numeric test involved playing back a test record 100 times and observing the before/after harmonic distortion. (LifeSaver reduced the THD after 100 plays btw.) LifeSaver is in the same class of treatment as Gruv Glide, as I understand it - it's basically a lubricant that reduces the coefficient of friction and so would have a direct effect on the temperature at the stylus-vinyl interface.
I'd figure the best way to confirm or disprove this is to measure the temperature of the stylus optically. Given the temperature increases thrown around (200 F at least), that ought to stick out like a sore thumb on any sort of temperature-sensing infrared camera. Just point it right at the stylus, and as close to it as you can get.
The price of thermal imaging is plummeting - you can buy a Raytek / Fluke thermal imager for what we once paid for one days hire of a thermal image analysis system, but it's still more than I can afford.Anyone out there with access to one of the new systems?
and he had a $10,000 infared camera with him that he used in his classes. We tried to use it on our house on a 25 degree day, in order to detect high heat loss areas. If your discussion had come up last weekend, we would have tested my turntable and cartridge interface.I will e-mail him, and ask that he try aiming the camera at his cartridge while playing a record. The only problem is that he may not be completely set up right now, as he was asking me about a new cartridge when he saw my turntable. I gave him some information about a new cartridge and where to purchase it, but I have no idea how soon that will be. If and when he plays his first LP, what should I tell him to look for while playing the record?? What type of readings do you want from this observation? Go easy on me, as I only have a BA in Microbiology 36 years ago that I never used.
He showed me the usual magic of momentarily placing your hand on the wall, then observing the heated hand print through the infared camera. Cool toy for $10,000!
Usually these things have a minimal spot for actual measurement of about 1mm but will capture relative temperature shifts on much smaller scales. The theoretical resolution limit is very small, of the order of ten um. Ask him what the resolution of his equipment is and we should be able to come up with recommendations for good images.I would be happy to post the images on my website once they are obtained, I am trying to build a collection of descriptions of the known limits to analogue performance.
of when he will have the time to do any of this. Not being a vinyl crazy like us and all this being long distance now will certainly drag this out. I kick myself that this didn't come up last weekend with this camera in my house! This individual also travels continually, as his actual job is to teach people how to use these cameras in their business or research. bill.
before the stylus is placed down on the record??
from his new 1 hour special on Comedy Central. long time fan....
nt
I started to watch that show but gave up on it. After a while his stuff is either too weird or it's just clever but not funny. To me anyway.
I always assumed that it is plastic deformation due to the high pressures involved....not any heating of the vinyl itself. Just pushing the vinyl out of the way.
IOW it bounces back quite quickly. Not in 24 hours.
Vinyl as used in records is used above its glass / rubber transition point so it acts as a rubber. It's very difficult to push a rubber beyond its compressive yield stress because it acts basically like a condensed fluid.When I get time I will try to get together more information on elastic/plastic deformation and creep strain behaviour in vinyl.
I think what you're saying is that vinyl as used in records is within its elastic region of the stress-strain curve, right? I agree - I think if it were anywhere near the yield, another material would have been selected a long time ago.Creep generally requires sustained exposure to temperature while loaded, as opposed to transient loading. In this case, what's posited is that the transient loading is accompanied by frictional heating. I don't believe in this situation the frictional heating could itself be contributing to heat-induced deformation - especially since the event is so transient.
I'll look forward to seeing more on this subject - it's been an interesting and enjoyable discussion.
As far as I'm concerned, the 24 hour rule has always been dead and you've just buried it.I'm still waiting for someone to come up with the fabled articles and photos that started this whole ridiculous concept. The proponents of the 24 hour rule, when confronted about the validity of their claim, usually reply by trying to shift the burden of proof to those who do not believe it.
So, does anyone who believes the 24 hour nonsense have any data which will discount Mr. Kelly's?
Well, I have always tried to adhere to the 24-hour rule because I read the articles and they made sense to me at the time. However, the 24-hour rule never hampered my listening because I always recorded my favorite records to reel-to-reel, cassette, DAT and now, CDR. Recording vinyl to another format has always been a major part of my hobby, so the 24-hour rule was never a problem.> So, does anyone who believes the 24 hour nonsense have any data which will discount Mr. Kelly's?
Well, all I can tell you is that as a result of my recording hobby, whenever I miscued and had to repeat the beginning of a recording, the peak signals were always about 0.5-dB lower on the second pass. When I discovered this, I felt the 24-hour rule was vindicated.
Of course, it is possible that any measurable difference may have been due to something happening other than deformation, whether thermally or mechanically induced, of the vinyl, such as heating or otherwise disturbing anything from the stylus through the cartridge and on down the signal path.Also, if the notion of actually moving vinyl is to be believed, movement of vinyl would enlarge grooves, would it not? Which would result in higher signal levels, would it not?
Vinyl is very tough stuff - it's hard to believe it can't take more than one pass of a record stylus every 24 hours without damage. Of course, the one thing I can say in support of the 24 hour rule is that we should all be listening to more different music!
well, higher tracking distortion levels yes, but I think it would tend to straighten out the groove by wearing away the most vicious excursions first.
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nt
IBSmiester
Open Your Ears....
Very interesting analysis. Of course, the 10 deg C rise is only that due to friction, and if accurate, is actually quite large when you consider the brevity of contact of the stylus tip and the surface of the groove.To get the total picture of temperature rise one needs also to include the heat conducted to the vinyl by the stylus tip (and I think Van den Hul's numbers may have been the tip temperature). The tip doesn't have much place to sink the heat from friction (the cantilever is so thin and light it might provide a little cooling but not much), so it likely does get warm during play.
However, even if one were to add this to the temperature rise due to friction, it's hard to imagine any significant heating of the LP as a whole, since any heat in the groove surface would very quickly be sunk into the LP itself.
Read the analysis again, it includes transfer effects from the diamond.
That is an interesting calculator - it's interesting to note the changes in outcomes as input variables are changed.Is 1.5 grams really 15 Newtons? I get about 0.015N by my reckoning. Of course, I live in a backward country where we still use pounds and ounces, so I'll let those in progressive locales weigh in on that one. Oddly, though, changing this variable seems to affect dT(bulk) but not dT(flash).
Since the effective velocity changes quite a bit as the stylus progresses, it's interesting to note that the temperature rise would be much greater at the outermost track than the inner. Seems like if temperature was the culprit in suspected 24hr or wear effects, outer tracks would be the first to go.
As for the transfer effects, I wasn't talking about conduction out of the interface (which it appears the model may include), but heat input to the surface from a diamond once it has warmed - clearly not included as it would require more information than the calculator uses.
You are of course correct, 1.5 grams is 15 mN not 15 N. I typed in the wrong value.Interestingly this increases the hotspot temperature rise as it reduces the actual contact area. The average temperature rise goes down however.
Oh, and I meant to say I agree - the 24 hour rule appears to be a well-intentioned but scientifically unfounded concept.The glass transition temperature of vinyl is somewhere around 80 deg C, so unless you keep your listening room around 70 C (about 160 F), the heat from playing won't take you anywhere the point at which the grooves will be permanently deformed.
I think even considering viscoelastic behavior, if any, there's no risk, since any deformation will be so transient as to have returned to nominal nearly immediately after the stylus tip passes.
Van Den Hul states on his website:"But the most important thing is record wear. I measured temperatures using a thermistor with a thin wire around the tip. A conical tip went up to about 140 deg C, but my one was 60 deg. I would like to come down further, but this was the lowest possible value."
I suspect his thermister is actually influencing his results.
Personally, I side with Mark's calculations.
JRags
"Always Searching for Perfection"
Diamond has the highest thermal conductivity of any known material and it is always in contact with the heat source so it is logical that the local temperature of the diamond will be higher than the local temperature of the PVC.Diamond also has one of the highest melting points of any known material so I don't think we need to worry about 160 oC.
Henry
nt
But my friends following the 24 hour rule are listening to a lot more variety of music.In a research lab, we took a thermal photograph of a record, then played it. There was absolutely no change whatsoever. We measured surface temperature as well. Same thing. As soon as the friction warms the vinyl the heat source is removed, so there is no melting.
That had to be the strangest urban method of all, that the diamond would fuse contaminants to the vinyl wall If that were true, your diamond would never build up dust!
Records don't feel at all warm after playing. Any warming is followed by immediate cooling. Even if it takes the vinyl a while to return to its previous form because one claims it is not very elastic, an immediate second playing will track a slightly different groove at the same original temeprature. This will not do any damage, but may delay slightly the return to the original shape. However, my tests supported by CD-R recordings, show no difference in playing the same section of a record ten times in one hour, and this indicates the groove returns to its original shape, if it ever got very far, very quickly.
Dave
Later Gator,
Crank up your talking machine, grab a jar of your favorite "kick-back", sit down, relax, and let the good times roll.The early bird may get the worm, but the second mouse gets the cheese.
> That had to be the strangest urban method of all, that the diamond would fuse contaminants
> to the vinyl wall If that were true, your diamond would never build up dust!You know, I had never thought of that. It makes sense, though. The stylus can't get real hot or the dust bunny would burst into flames.
I think they still recommend flint and a knife for fire starting.If I showed up at a campout with a turntable I think they would have me committed!
;-)
Hope you have a great weekend! I am still building 2006 plinth number 4.
Also thanks very much for the discs. I'll get Going Home out to you soon.
but I couldn't (then) recall the term "bunny", tx for that.Back then 480 °F was being banndied about ... see the post I responded to, the OP many be interested in the extended quotation that post contains ... and now we're talking less than 20 °F!
No Guru, No Method, No Teacher
- http://db.audioasylum.com/cgi/m.mpl?forum=vinyl&n=580978&highlight=burn+bjh&session= (Open in New Window)
nt
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