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OCAU News |
Exploding CD Theories
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Tuesday, 29-May-2001 20:13:27 (GMT +10) - by Agg
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Well, 27 people offered suggestions. :) Pretty much everyone had experienced it first-hand. A couple of people thought that at high speed the disk may wobble on the spindle until it hits a stationary part of the drive.. hmm, seems unlikely to me, or unlikely to make the disk explode, anyway. A lot of people mentioned stickers, paint, printed labels etc unbalancing the disk and even the possibility of cheap disks being unevenly weighted or having the hole not properly centred, resulting in catastrophic vibration. A couple of people suggested that there's a "natural vibration" and at certain RPM's the cd might resonate (like the old "soldiers marching over a bridge" thing) and disintegrate. Rick suggested cold weather making them brittle - Manaz and Daniel both say they've seen it when CD's are cold, as when kept in a server room, then put into a CDROM drive that heats them rapidly - some suggested the heat from sustained use as in a long installation could be to blame. Similarly, some suggested "plastic fatigue" caused by flexing or banging/dropping the CD. Memphis noted some special CD carriers place too much stress on the hole in the CD. Ian says old CD's often have hairline cracks near the spindle which could be an indication of fatigue due to age or stress.
Several people mentioned that Sony CDROM drives (certain 48 and 52 speed ones at least) have a sticker (picture linked below, thanks Greg) which warns that under certain conditions disks may break at high speed rotation:
Click to enlarge (26kb)
Wilhelm rigged one up to his Dremel to see how fast it could spin: Starting off slow at around 5000 RPM nothing happened but around 8000-14000 RPM the thing just completely shattered and bits were scattered all over my dorm room. It scared the hell out of my roommate too.
Kurama notes it can be quite serious: There was a class action court case in Taiwan last year over exploding CDs. The CDrom manufaturer was sued (can't remember which one) and they settled out of court with some compensation.
Anyway! What does it all mean? :) Clearly exploding CD's are uncommon but not exactly rare. The central theory seems to be this: the plastic disks seem prone to microfractures due to poor production, age or physical stress. A damaged or prone-to-damage CD in a high-speed CDROM drive can suffer a catastrophic failure which, as it happens while rotating at speed, can have very energetic and spectacular results. The secret to avoiding it, I guess, is to not stress the CD's (no bending, stressing the spindle hole, dropping or rapid temperature changes), don't use old CD's or just use slow CDROM drives.
Much more practical I think is to use high-quality CD's and make sure, as with ANY media, that you never have only one copy of important data.. and certainly not stored long-term on a CD you intend to use in a fast drive. What do you expect for media that costs you $1. :)
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