Should have written "I know how to calculate the temperature elevation", for my first sentence above. Q is in joules, a unit of energy. Thus Q. would be equal to the kinetic energy generated by friction between stylus and groove, a function also of velocity, because neither the stylus tip nor the groove can dissipate energy any other way, except as heat. (But that's the rub; some energy is probably dissipated in "stretching" the groove walls, too.) Being in biology has nothing to do with this; I never studied physics except in college, so I hope the above is correct. |
The comment about a human being able to survive for 45 minutes at over 400 degrees fahrenheit has very little to do with wooden tonearms, as well as being untruthful. I suspect that in a sealed chamber, at that temperature, the first real breath and a human body would know that death is very close.
I believe the comment about the level of heat generated at the stylus/ vinyl interface during replay was made in counter to someone else's comment suggesting that movement within a wooden tonearm due to atmospheric variations would be sufficient as to make an accurate and stable cartridge setup with a wood-wanded tonearm, impossible, or even difficult, which is just not true. Someone laid out some figures about movement in wood without telling the whole story. First, different woods move different amounts. Second, wood movement occurs radially at a much higher rate than it does in a longitudinal direction. Making a tonearm wand that stays true to it's axis can be accomplished easily enough if care is taken. Change in length of a wooden tonearm wand is pretty much a non issue given the short length of the wand, the fact that it is stabilized, and that wood just does not move that much longitudinally.
Also, that significant heat is generated at the stylus is not really a problem. Who knows though.. maybe the next significant advances in cartridge technology will come with nano-liquid cooled cantilevers ;) |
Swampman, by the way, I am in the sauna at the club frequently for periods of ten minutes or more. The thermometer in the sauna reads more than 210 degrees F most days. No prob-prob-problems here. |
You are going to have to make many assumptions to do this calculation. First the heat Q being dumped into the diamond stylus is at the same time being dissipated by the stylus assembly to its surroundings. This will involve the temp. difference between the diamond and its surroundings, geometry of system, heat conduction coefficient, heat capacity, etc. Probably best to determine the equilibrium temp empirically. Heat dissipation calculation involves a nasty partial differential eqn. Then there is the vinyl: it is moving, constantly exposing new room temp. vinyl.
The heat dumped into the stylus will equal its dissipation at its equilibrium temp.
Presumably the rest will be dumped into the vinyl. Temperature will depend on heat capacity of the vinyl and how fast it is conducted away (that nasty heat conduction eqn. again).
Now the heat generated Q as the result of friction, as has been already mentioned, depends on the pressure, coefficient of friction and velocity. Now the linear velocity is changing do to the change in radius of the record as it plays. Then there is the stylus velocity due to the music. Now this velocity is frequency dependent (increases linearly with frequency).
So, assumptions need to be made to calculate a ballpark figure: like an average stylus velocity. I would assume that the dissipation of heat from the stylus is small and can be ignored. With that we can assume that all the heat generated is dumped into the vinyl. Heat conduction in the vinyl is probably small enough that one can assume that for an instant all the heat is contained in a small volume (but how small?). That would have to be addressed since heat capacity calculations require a mass to calculate a temp. .
So, this simple little calculation turns out to be a bit of a sticky wicket. |
Geoff, I have to side with the others; I think you'd be looking like a baked potato after even 10 min at 445 degrees F.
Probably the best way to determine the temperature developed at the stylus contact point in the vinyl would be to point a laser-based temperature sensor at the contact spot, during play. One interesting thing that fell out of this particular discourse is that most likely the outer grooves heat up more than the inner grooves during play, because the angular velocity of the stylus tip, and therefore the kinetic energy that has to be dissipated, is greatest at the outside edge of the LP surface. But on the other hand, the groove undulations may be less tortuous at the outer grooves, thereby reducing friction compared to inner.
Anyway, I agree with Ilikmangos, as one might imagine. |
Lewis, I didn't say 445 degrees, I said 425 degrees. I'll take every degree I can get. Lol You guys ain't thinking about this the right way. Humidity is the thing that kills you. You can stand very high temperatures if the humidity is near zero. As I said I've been in the sauna at the gym when the air temp is over 212 degrees, I.e., boiling. Hel-loo! |
Listen up, this just in...
"Who knows. But I read in Guinness Book of World Records that the US Air Force did experiments back in the 60's where they subjected naked men (briefly) to 400 degrees F, and heavily-clothed men to 500 degrees F with no ill effects."
Cheers, GK |
If I were suddenly thrust into 425 degrees, I'd grasp for anything in panic.....
even The Teleportation Tweak. What else is there to lose... :) |
Geoff- if you look at the graph in the appendix of that paper, you will see that the temperature vs humidity effect is acconted for and when you extrapolate back to 0% relative humidity you can see that the maximum 45 minute tolerable temp is a tad over 160 degrees. And I'd be hard pressed to believe that they would subject the officers to something they had not tested on the enlisted men first. Remember that an internal temp of 165 degrees is well done for a piece of meat, which of course is what we are. To say nothing about heat stroke, which is classified as a medical emergency and occurs when your core temperature exceeds 105 degrees. Sorry, I ain't buyin. |
Swamp, you made a few very good points
Geoff, how can you maintain that raw humor basted @212 degrees? :) |
Isochronism, if you walk into the sauna at 220 degrees directly from the Steam Room next door at say 140 degrees it actually feels like room temperature in the sauna, at least for the first few seconds. Hint: it's the humidity. I be been in the sauna at 220 for up to twenty minutes, no ppppproblem. |
