I’m in the process of ripping all my music CDs. Yesterday, I loaded the DVD drive of one of my PCs with a CD that I burned at least 10 years ago. It had some scratches and the last time I played it, it skipped at some places. But I thought I could give it try and left the house to visit a friend and let CdEx (the ripping tool) do its job. Big mistake…
When I returned, I tried to eject the CD to no avail before I noticed that it was blocked by a broken piece of the disc that got stuck. So I disassembled the drive to find that the CD had been literally shredded to a few larger and hundreds of tiny pieces. You could’ve used the drive as a rattle in a samba band. I have heard of incidents like this before, but was stunned nonetheless. No I wonder how fast the drive must have been rotating before the centrifugal force was big enough to cause this damage.
The good thing, though, is that after cleaning the drive from all the debris as best as I could, it’s still working.
Has anybody of you ever had a similar experience? And how can it be that the rotational speed of the drive isn’t limited in any way?
Faster spinning = faster data reads. This is actually a known problem with super-high-speed drives. The weaker substrate of older CD-Rs can’t sustain the inertia and shatters. One of the very early episodes of MythBusters has them gleefully shattering CDs by hooking up a drive spindle to a large drill motor.
I know this, but I assumed that the maximal speed of a drive shouldn’t be enough to shatter any kind of disc that is compatible with it. But the rest of your post gives a good explanation.
Your ripping software probably has a setting to slow the drive down from 48x or whatever to slower speeds. Next time you’re ripping an old or homemade or damaged CD, take the safe way & slow the drive down to 2x or 4x. Yeah, it’ll take 15-30 minutes to copy the CD off to HD. But the CD will survive & you’ll get a complete.
It IS limited. They could be built to turn at 300x, but the engineers know that almost all CDs/DVDs would shatter under that much force. 48x is as fast as you can be sure (ie. 99.somenumberof9s likely) that a healthy modern CD/DVD will survive. And a non-healthy CD (ie one with microcracks already, or gunk stuck to it so it isn’t balanced) can shatter at plain old 1x audio playing speeds.
If you’re asking why there isn’t a sensor in the drive which can detect the CD/DVD is about to come apart … The problem is that the plastic is brittle. So as the stress builds from cetripetal/centrifugal force the disk is fine until it fails spectacularly in the space of a millisecond or two.
Yes, that’s an eternity to modern electronics, but once the failure sequence starts, there isn’t time to spin down the mechanical parts enough to reduce the stresses before the disk is in several pieces.
I would only add that the plastic could have lost too many of the plasticizers that allow it to flex and hold it together. Heat, time, and light can make this happen faster. The chemistry of the plastic is also a factor. It would be interesting to take one of the bigger pieces left over and bend it to see how fast it cracks. If if breaks like a leaf, oxidization is more the cause than speed.
Just got home from work and browsed my wastebasket for some larger pieces of the shattered CD. But no, they didn’t crack easy at all, so it seems it wasn’t a case of oxidization.
I just had a recordable CD explode into shards in a DVD drive for the first time a few days ago – just heard a loud POP shortly after I put it in. Had to replace the drive – it wouldn’t close after I shook out all the pieces.
As I mentioned, I was luckier and the drive survived (by now). The mechanical and optical parts seem to work fine (I since have ripped about 20 CDs without problems), but I’m a bit concerned about the little specks from the metallic layer. It was impossible to remove them completely (I had no compressed air at hand when I cleaned the drive), so I worry about a possible short on the drive’s board.