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View Full Version : Why don't CD's get hot?



Nikuk
03-20-2005, 11:03 PM
So, friction is the enemy of all things that want to move... right? if a CD is spinning around at high RPMs... why doesnt it get hot enough to melt? Especially when it's already being preheated by a laser...

JimJ
03-20-2005, 11:06 PM
You'd need some serious speed to build up enough air resistance on the leading edge of the disc to heat it significantly...

I do notice that CD's are warmed slightly if I've been playing them for several hours on end - but then again, the entire player is warmed as well.

swaptrex
03-20-2005, 11:07 PM
they do get pretty hot though.

monte_carlo97
03-20-2005, 11:07 PM
There is very little friction on a cd so that is builds up engouh air resistance to turn that energy into heat.

Nikuk
03-20-2005, 11:12 PM
what about the resonance of the cd?

Echo42987
03-20-2005, 11:14 PM
The cd's have some kind of coating on them as well. Thats why you can't scratch them. Because when you do the next time you put it in that part of the disc will melt, therefore creating the disc to skip

Strecker25
03-20-2005, 11:15 PM
i overheated a pc once and melted the housing of the laser to its worm gear

that ******





wait no it was sweet

Nikuk
03-20-2005, 11:21 PM
The cd's have some kind of coating on them as well. Thats why you can't scratch them. Because when you do the next time you put it in that part of the disc will melt, therefore creating the disc to skip


so its not that difficult you say?

formlua5150
03-22-2005, 02:44 AM
The cd's have some kind of coating on them as well. Thats why you can't scratch them. Because when you do the next time you put it in that part of the disc will melt, therefore creating the disc to skip

Really? I've scratched plenty of cds

cjjackson85
03-22-2005, 02:46 AM
IIRC, they are cooled from within by liquid nitrogen. ;)

VOA_NIGHTMARE
03-22-2005, 03:13 AM
I can tell you though in my experiance. In my car now how my cd player is, I had one cd player that would get very very hot, i think it didnt help because of it being winter at the time and stuff but its right by the vents. And once I got driving for about 1 hr or so the cd player would get so hot and the disk that it wouldnt play, and if it did it was a wierd noise and all distorted. But it got so hot that when I would eject a cd, I couldnt grab it, and I am a cook, and I grab hot stuff all the time. So my hands can handle alot more heat than most people. I thought it was weird.

Nikuk
03-22-2005, 09:51 AM
IIRC, they are cooled from within by liquid nitrogen. ;)


see, now that I could understand. But, wouldn't it make the disc too brittle?

hoss
03-22-2005, 09:54 AM
well yeah it would make them brittle if they used regular nitrogen... but not if you use monohydorxenated de ionized sulfate free nitrogyn. duh.

Nikuk
03-22-2005, 09:59 AM
****! thats right! hoss, you're still the man. :thumbupw:

monte_carlo97
03-22-2005, 12:10 PM
well yeah it would make them brittle if they used regular nitrogen... but not if you use monohydorxenated de ionized sulfate free nitrogyn. duh.
oh god. you know too much for your own good.

squeak9798
03-22-2005, 12:19 PM
CD's?!?! Who uses CD's :confused:

8-track is where it's at

nismboy6986
03-22-2005, 12:19 PM
if i'm not mistaken a cd only turns at 250 rpm on the outside and 500 rpm on the little round thing on the iside and no i don't understand that. and thats not fast enough to create that much friction anyway since the only thing that actually touches the cd when its spinning is the hub. and the laser is a relative low power laser that can only really damage your eyesight. isn't the reason why you can't scratch a cd is because theres a bunch of lil microscopic flat and low spots that the laser measure as 0's and 1's hence why cd information is digital.

Black_Jesus
03-22-2005, 12:21 PM
if i'm not mistaken a cd only turns at 250 rpm on the outside and 500 rpm on the little round thing on the iside and no i don't understand that. and thats not fast enough to create that much friction anyway since the only thing that actually touches the cd when its spinning is the hub. and the laser is a relative low power laser that can only really damage your eyesight. isn't the reason why you can't scratch a cd is because theres a bunch of lil microscopic flat and low spots that the laser measure as 0's and 1's hence why cd information is digital.your mistaken :) badly lol

nismboy6986
03-22-2005, 12:35 PM
so i fast does a cd turn?

req
03-22-2005, 12:37 PM
your mistaken :) badly lol

maybe about the RPM's, and kind of misinformed about the 'high and low' spots.

there are LOW spots that the lazer will burn. this is why its called 'burning"... we cant burn 'high spots' LOL :)

but the disc will break apart before it melts. its getting cooled by the air that its spinning against (of what amount of air that is :p:) ive seen tests where they put a disc on high RPMs to see at what point they break. and it wasnt much. but not nearly fast enough to melt. and dont forget, they arent being forced against lots of molecules of air eaither - because they are spinning on a flat plane, and that TINY edge would need to be in contact with alot more molecules of air faster to get that hot.

i dunno. thats my 2c

Black_Jesus
03-22-2005, 12:43 PM
so i fast does a cd turn?~10,000 rpm. but depending on the drive it can be a little faster or a lot slower

req
03-22-2005, 12:45 PM
thats what i thought, but i didnt recall exact numbers so i didnt throw them out.

FYI - a harddrive spins at 5400, 7200, or 10,000 (or faster, depending ons scsi or whatnot)

Black_Jesus
03-22-2005, 12:49 PM
mmm scsi...

im still running good ol ide *slaps maxtor*

nismboy6986
03-22-2005, 01:13 PM
i think you are thinking about computer drives. i'm talking about a regular cd player. and you mist interpreted what i said. i ment the unrecorded cd would be flat but the recording laser would burn a bunch of microscopic pits in the cd and the playback laser would measure the difference between the flat spots and the pits and would consider the flat spots to be the 1's and the pits to be the 0's or vice versa.

UndercoverPunk
03-22-2005, 01:20 PM
My CD's never get hot, I spray a constant feed of R-12 into the case of the player. I go through a 30lb tank in about a week. Sure its expensive, and probably is the reason why we don't have real winters anymore, but the SQ I gain is worth it!:D

Oh and it's been proven that CFCs add dB's. How else would I hit 11ty Billion?

Black_Jesus
03-22-2005, 01:22 PM
i think you are thinking about computer drives. i'm talking about a regular cd player. and you mist interpreted what i said. i ment the unrecorded cd would be flat but the recording laser would burn a bunch of microscopic pits in the cd and the playback laser would measure the difference between the flat spots and the pits and would consider the flat spots to be the 1's and the pits to be the 0's or vice versa.i believe the cds (like you buy from stores... retail cds) are stamped into the pattern, 0's and 1's and not written with a laser. but your analogy with the 0's and 1's is right on the cds. not sure what kind of rpms normal disc players use, put it this way though. the more it skips from jolts and such, the slower the cd is spinning in the unit. lol

squeak9798
03-22-2005, 01:25 PM
ive seen tests where they put a disc on high RPMs to see at what point they break. and it wasnt much.

According to Mythbusters, it's around 30k to 35k IIRC :)

LoudCrownVic
03-22-2005, 01:28 PM
Never had a problem with CD's getting hot just while turning- though I have gotten the HU amp to toast them pretty good by running like 6 speakers on one channel...

req
03-22-2005, 01:35 PM
According to Mythbusters, it's around 30k to 35k IIRC :)

really? i remember it being alot less than that. hmm. like i said, i didnt wanna give out numbers because i seriously didnt remember :)

as for the stamping, imagine a pancake of metal the size of the disc, with MINITURE needles on the surface. each disc goes thru, STAMP, then the second coating is put on.

thats how they are stamped (i believe - dont quote me)

Acidburn
03-22-2005, 03:24 PM
CD's?!?! Who uses CD's :confused:

8-track is where it's at

go back to the retirement home

JimJ
03-22-2005, 03:47 PM
CD's?!?! Who uses CD's

vinyl > all

'nuff said.

Nukedsodapop
03-22-2005, 04:33 PM
Our DVD drive wont work anymore cause a cd shattered in it.... there was cd everywhere and probably still in the drive.... but it left marks lol so yeah I didnt think the Mythbusters thing was real until that happened....

Nikuk
03-23-2005, 10:35 AM
Ah HAA! Proof!

azazel
03-23-2005, 11:24 AM
Any heat that you feel on a CD after you remove it is caused by heat from the internal amplifiers of the unit itself. The laser does not heat the CD up at all because it is a low energy laser shining on a reflective surface (like it should).

monte_carlo97
03-23-2005, 03:34 PM
Any heat that you feel on a CD after you remove it is caused by heat from the internal amplifiers of the unit itself. The laser does not heat the CD up at all because it is a low energy laser shining on a reflective surface (like it should).
that was also my understanding of why cd's always got hot.

Nikuk
03-23-2005, 04:18 PM
:eek:

yz_gt69
03-23-2005, 10:07 PM
good way to prove that it's the HU heating it up= play ur system til the cd gets hot (however long) take it out, put in a different cd, the time it takes to heat up the 2nd cd should be considerably less... I would suggest, however, getting a life. (becuz i thot of this, i mite just take my own advice)

monte_carlo97
03-24-2005, 09:52 AM
that is just because your canadian.






















Naw, just playin.

Nikuk
03-24-2005, 10:11 AM
good way to prove that it's the HU heating it up= play ur system til the cd gets hot (however long) take it out, put in a different cd, the time it takes to heat up the 2nd cd should be considerably less... I would suggest, however, getting a life. (becuz i thot of this, i mite just take my own advice)

You sir, are an idiot.

yz_gt69
03-24-2005, 09:14 PM
So, friction is the enemy of all things that want to move... right? if a CD is spinning around at high RPMs... why doesnt it get hot enough to melt? Especially when it's already being preheated by a laser...

^ I won't take your comments to heart