Experts in a spin over killer CDs

[BJ_M]

Experts in a spin over killer CDs





After years of helping us go faster, computer and consumer electronics makers may soon echo road safety campaigners in urging us to slow down or risk injury and death.

Researchers in Sweden have found that today's state-of-the-art fast CD-ROM drives and DVD players can shatter discs, sending out knife-like shrapnel at near the speed of sound, causing injury and damaging equipment.

At close proximity the shards tear into 3 millimetre-thick aluminium, or 1 millimetre-thick steel, and mince through soft body tissue, according to researchers.

In a score of tests conducted at engineering firm Atlas Copco's labs on a variety of CD and DVD discs, from boxed software to recordable media, researcher Jorgen Stadje found most were unable to sustain the high revolution speeds of the fastest drives.

CD-ROM and DVD-ROM drives permeate much modern equipment, from home and office PCs to in-car navigation systems, console game systems and portable notebook computers.




"CD-ROMs could be hazardous to your health, and DVDs even more so," Mr Stadje said.

"At too high RPMs they blow up with a bang and could, in the worst case, cause injury to persons."

He blames device makers for trying to best each other over who has the fastest drive. But while drives are getting faster, the relatively fragile disc media is not keeping pace.

"There is a limit that cannot be transgressed - the plastic's tensile limit. Unfortunately, some manufacturers have already passed it and we have had e-mails from many on the Internet who have experienced fractured disks," he said.

"Earlier experiments have shown that shrapnel is capable of tearing up holes in the roof and crack aluminium sheet. This is a potential consumer problem waiting to happen to many buyers of a new generation of players."

CDs and DVDs, called "optical" discs because their data is read by laser light, have their performance rated by multiplying from a base speed.

Mr Stadje suggests owners of PCs and digital video equipment should sit at least five metres from their equipment.

He also urges users to consider wearing protective goggles and clothing possibly made from kevlar, a material usually used by the military and police forces in the manufacture of soft body armour.

http://theage.com.au/articles/2002/12/09/1039379784015.html

[Craig Tucker]

Do you think the sticky labels will hold them together

[epo]

well, well, well... To spit out fragments at the speed of sound CD has to make at least 55000 RPM. That's a kind of turbine
What is name of the cult hosting this web-site?

[BJ_M]

i guess i better not let him know about glass platter laser disks which have been around for years and make a big bang when you throw them against the wall (and look great spining in the air)

[SLK001]

well, well, well... To spit out fragments at the speed of sound CD has to make at least 55000 RPM.

Well, not quite. Let's do the math:
Diameter (D) of CD = 5.25"
Circumference (CIRC) of CD = pi x D = 16.5" = 1.37' (feet).

The speed of sound is approx = 1100 ft/sec

For the linear velocity of the outside edge to reach the speed of sound, we will use:

Linear Velocity = RPM x CIRC, or what RPM will give us 1100 ft/sec.

Cranking the numbers gives us 800rpm. Anyone know of an 800X CD recorder?

This assumes that when the disk shatters, the former component parts will remain at the velocity they had at the moment of "rapture" via tangential translation. Or something like that.

Feel free to translate into your desired units of choice.

[BJ_M]

Yamaha says thier CD-r drives spin at over 9000 RPM when writing to the inside of the CD, and elsewhere 5000 to 7000 -- this is only for a 24x writer ..

you were assuming a 1x write would equal 1rpm in your calculations ..

this means that the newer 40x - 72x writers prob 10k rpm and up ..
which means a min. of 10x speed of sound ..

[snowmoon]

Hmm...

http://www.technosound.com.cy/nqcontent.cfm?a_id=1512

RPM of between 10,500 and 2000 rpm. Well abouve the 800 you calculated necessary to break the sound barrier. I suggest you do a little more research before trying to debunk others posts.

I wonder when people will finally learn and figure out a new way of acessing the media via multiple parallel heads to increase throughput wihtout increasing the speed of the spinning. Or mabye they can spin the head in an alternative direction since it's usually made of metal and less likley to fly apart at high speeds.

[BJ_M]

Hmm...

http://www.technosound.com.cy/nqcontent.cfm?a_id=1512

RPM of between 10,500 and 2000 rpm. Well abouve the 800 you calculated necessary to break the sound barrier. I suggest you do a little more research before trying to debunk others posts.

I wonder when people will finally learn and figure out a new way of acessing the media via multiple parallel heads to increase throughput wihtout increasing the speed of the spinning. Or mabye they can spin the head in an alternative direction since it's usually made of metal and less likley to fly apart at high speeds.

the Kenwood CD uses 7 heads in their 72x reader -- so it is really a 24x reader i understand .

[SLK001]

Wasn't trying to debunk anyone. Just illustrating that the sound barrier is broken at the edge at 800RPM on a 5.25" disk (instead of 50,000+). This is regardless of what you are doing with the disk. You take a piece of plastic that is 5.25" in diameter and spin it that fast, and you break the sound barrier.

My mistake, thought, about the 800X drive. 1X for a CD-R is ~ 300kB/sec.

[sammie]

Actually, this has been in the news for the last couple of weeks. Evidently the manufacturers are all well aware of this and the 48x - 52x limits we see are at least in part due to this. Presuming that they don't want to be sued for destroying computers or households, I think we are pretty safe from flying CD bits. It does make one think twice about banging the computer around while the disk might be spinning (come-on we've all fished behind the box for something while it was running). It also makes me think twice about using an el-cheapo cd-r in a laptop in its namesake mode!!! Yow, that would be painful/embarrassing.

[tenders]

killer discs??? hmmm...........i'll run right out and get a bullet....er...disc proof vest.

[Conquest10]

yeah i read about this in pc world a couple of months back.

[shaham75]

Start a new thread if you want to ask a question, and only post it in one forum.

Edited by Craig Tucker

[BJ_M]

no post

[Timoleon]

...reminds me of the stories (apocryphal or not) about flywheels breaking free from under the hoods of certain makes of cars and coming through the dash and decapitating the luckless passengers... "Tis a sad and dangerous road we travel. Maybe we should get Ralph Nader to kick the asses of the evil CD drive makers...

[cfitz]

Wasn't trying to debunk anyone. Just illustrating that the sound barrier is broken at the edge at 800RPM on a 5.25" disk (instead of 50,000+). This is regardless of what you are doing with the disk. You take a piece of plastic that is 5.25" in diameter and spin it that fast, and you break the sound barrier.

My mistake, thought, about the 800X drive. 1X for a CD-R is ~ 300kB/sec.

CD diameter = 12 cm / 2.54 cm/inch = 4.72 inches, not 5.25 inches
circumference = 14.84 inches = 1.24 feet, not 1.37 feet
Linear velocity at edge = RPM x CIRC, but don't forget 1 minute = 60 seconds (RPM = revolutions per minute)

Speed of sound varies with altitude, temperature, humidity, etc, but we will stick with 1100 fps (feet/sec) as a round number:

1100 feet/sec * 60 sec/min = 66000 feet/min

RPM = 66000 feet/min / 1.24 = 53,400 RPM

epo had it right all along.

By the way, 1x CD transfer speed is 150 KB/s

cfitz

[cfitz]

Yamaha says thier CD-r drives spin at over 9000 RPM when writing to the inside of the CD, and elsewhere 5000 to 7000 -- this is only for a 24x writer ..

you were assuming a 1x write would equal 1rpm in your calculations ..

this means that the newer 40x - 72x writers prob 10k rpm and up ..
which means a min. of 10x speed of sound ..

The highest speed writer currently in production is 52x, although 56x has been announced. There isn't any expectation of going higher at this point.

Most all new high speed drives write in CAV mode at their top speeds (there is one that still uses Z-CLV), meaning they spin at the same RPMs throughout the whole burn. A typical 48x or 52x drive starts out around 20x and ramps up linearly from there as the laser moves to the edge of the disc. So it is a mistake to extrapolate 9000 RPM for 24x to, for example, 18000 RPM for 48x. The highest rotational speeds currently reached are in the 10,000 - 11,000 RPM range.

By the way, that picture you linked came from CDRLabs.com. I always like to reference the source whenever I borrow material from another web site.

Here is a discusstion on cdrlabs.com that does addresses this topic:

http://www.cdrlabs.com/phpBB/viewtopic.php?t=7597

The article BJ_M quoted from theage.com.au is nothing buy scare-mongering.

cfitz

[BJ_M]

i dont think anyone here took any of it as seriously as you did

[cfitz]

I wasn't aware that I took this any more seriously than any of the other posters here who took the time to contribute information regarding the nature of high speed burning, including you.

Some people have expressed real, but unfounded, concern about high speed optical drives in various forums, so I decided to provide some concrete information for anyone who might read this and think it is a real problem. What you see as a joke can be a real concern for someone who doesn't have much experience.

In any event, there was enough misinformation in general about CD burning in this thread to warrant a correction.

cfitz

[BJ_M]

true, and thank you ..

btw i had not interpolated higher than than what i posted in max rpm's .. the max speed i got from a plextor service manual.
the 72x i was refering to was a reader - i should have said so , but kenwoods 72x reader uses multiple heads (i think 7) so rather hard to say what true speed is ... hard to say exactly on any of them without measuring them with a tachometer or scope .

i doubt there is anthing in a cd player/writer - even with particle acceleration or mass increase due to its kinetic energy at faster speeds - that is moving fast enough to cause Cerenkov radiation. So we all can sleep a little easier tonight. 8)

[cfitz]

btw i had not interpolated higher than than what

Yes, I realize you didn't. You accurately posited speeds of around 10,000 RPM. I was just cautioning people in general from doing so.

the 72x i was refering to was a reader - i should have said so , but kenwoods 72x reader uses multiple heads (i think 7) so rather hard to say what true speed is

Yes, 1 laser split into seven beams. It was hard enough to do for reading - I don't think anyone has any plans of trying to do the same for writing. Imagine all the linking that would have to be done...

i doubt there is anthing in a cd player/writer - even with particle acceleration or mass increase due to its kinetic energy at faster speeds - that is moving fast enough to cause Cerenkov radiation. So we all can sleep a little easier tonight. 8)

true, true - particularly if we sleep under lead-lined kevlar sheets...

cfitz

[Bagmaster]

Well folks, I can tell you from experience that speed kills, hehe. I've had 3 disk to explode in 3 different cd-rom drives at 48x, 52x, and 56x speeds. Sounds like a bomb going off, smoke pours out of the tray, tray door gets blown off and makes you jump for the ceiling. It even bent the motor spindle on a new 56x and I had to junk it. 40x seems to be ok, no problems with it yet.

Faster is not always better.

[BJ_M]

kewl - i want one ..