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Thread ID: 56649	2005-04-11 10:32:00	Shattered CD in drive!!!	Monkfish (7860)	Press F1

Post ID	Timestamp	Content	User
343721	2005-04-12 06:33:00	It's normally only a problem with data CDs and some drives limit to 40x unless you over-ride. The offending CD was a Kiri Te Kanawa audio disk that normally wouldn't have to spin faster than 1x ??? Maybe she's getting past it :-)	PaulD (232)
343722	2005-04-12 07:41:00	biff the drive out...........new ones are only about $50 ......	drcspy (146)
343723	2005-04-13 00:51:00	The "standard" 1x speed is 300 rpm. 52X is 15,600 rpm. The centripetral force is fairly large. :( There was a thread on this subject a while ago, and I posted a URL to a research organisation which made the calculations and di some tests (in an armour plate box;)). It's not too difficult to dismantle the drive (just use "wiggle" rather thabn brute force). The laser is the least likely part to be destroyed. It's built into the optical assembly. The problem is smallish bits jamming the gears and rack and pinion motions.	Graham L (2)
343724	2005-04-13 01:12:00	With a bit of searching I've found my original posting, here (pressf1.co.nz). A search for "exploding CD guy" will get the full thread and few others.	Graham L (2)
343725	2005-04-13 02:46:00	biff the drive out...........new ones are only about $50 ...... One should not have to fork out their own money, even though it's "only about $50", for a new drive if it's damaged through no fault of their own. Even if the media was defective to begin with, it is the supplier or publisher of the media that should provide a replacement for consequential loss / damage. If the drive had an imbalance that caused the disc to be scratched or otherwise damaged when spinning at high speed (which sets off the chain reaction), then the drive manufacturer is responsible. The hard part is proving whose fault it was - CD retailers or publishers are likely to claim it was the user's negligent use / storage, or otherwise try to shift the blame. Retailers could damage the CDs in their handling (since they keep them out of their cases until being sold, for security reasons), and publishers may have simply let defective discs slip through due to poor quality control. Bit of a Catch-22 for drive manufacturers - how can they analyse the drive to prove whether it had an alignment problem if it is damaged by the shattering CD? Could make a good story for the likes of Fair Go. ;)	D. McG (3023)
343726	2005-04-13 03:18:00	This was an audio CD . It was fit for its purpose . It would have survived "for ever" if it had been run only at the speed required by the CD standard: 300 rpm . If a user puts an audio CD in a computer drive where it will be spun at up to 52X that standard speed, it's not the disk supplier's problem if it explodes . A disk drive is unlikely to be significantly out of balance . The manufacturers know how fast it will spin, and the design is by engineers . This wouldn't cause a disk to break anyway . The users would notice this problem, probably before anything else happened . CDs can be out of balance . Some audio disks might have significant amounts of ink for fancy artwork, but this would be no problem at 300 rpm . Some users put paper sticky labels on CDs . This is a Bad Idea . But it's not the drive manufacturer's fault . Fracture is caused by a combination of factors . I suspect that there must be a physical fault added to the large stresses at high speeds . A stress concentrator like a scratch or a crack at the hub would usually be needed . You've got to remember that the CD was designed for audio use twenty years ago . The standard CD obviously has ample strength . . . they rarely break in this way even when run at 50X the design speed . The strength is probably a result of making the disk stiff enough and capable of withstanding handling . The high speeds of computer CD drives is a response to customer demands . I doubt if anyone has made a X100, or even a X75 speed CD ROM drive . I'd bet that someone worked out the safety factor based on the physical charcteristics of polycarbonate, and 52X is the practical limit . But that would still rely on undamaged disks . And that's the user's responsibility . It's obviously not a "safety" thing . . . there have been no reports of people being injured by exploding CDs . Remember glass beer flagons? The "half-gee"? They exploded frequently, often causing injury . The glass manufacturers sold the jars as "80 oz Winchester" bottles, with the explicit statement that they were not a pressure vessel . The quality control did not include pressure testing . Soft drink bottles were pressure tested . (I remember one small company's bottle would stand 1000 psi) .	Graham L (2)
343727	2005-04-13 04:29:00	The 52x speed probably uses CAV ie only the tracks at the outer edge read at 52x at around 10,000rpm. I don't think there are any that can read inner tracks at 52x. There was a drive that had several lasers reading in parallel to achieve ~70x	PaulD (232)
343728	2005-04-13 07:12:00	But Paul, if the motor is spinning at 52x, then the inside, outside and everything in between will be too. Of course, that doesn't mean it reads at 7.8MB/sec, but it's still spinning at that number of RPM.	george12 (7)
343729	2005-04-13 10:24:00	I've linked you to the answer before George. The data track is a spiral starting at the center, as the laser follows the track outwards the head reads more data per revolution. The speed (52x) refers to the max read/write rate not the rpms	PaulD (232)
343730	2005-04-14 01:29:00	I've linked you to the answer before George. The data track is a spiral starting at the center, as the laser follows the track outwards the head reads more data per revolution. The speed (52x) refers to the max read/write rate not the rpms But Paul, the standard rate of 150 kB/s is at 300 rpm. A 52X drive must at least peak at 52X300 rpm. It is the high rotational speed which can burst a CD, not the data reading rate. I have always assumed that the 52X is the data rate on the outer track.	Graham L (2)
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