Re(2): Science of making CD's, more OT

[Per Mattsson]

ka4hjh at gte.net skriver:
>The rotational speed of the disc varies from about 500 rpm to 200
>rpm from the inside to the outside to maintain this data rate. This means
>that a 32X CD reader is whizzing around at up to 16,000 rpm! (and over
>4MB/s--faster than a lot of hard drives can sustain). No wonder they tell
>you not to put shaped discs in them!

A magazine in Sweden just did some test on CDs spun at true 32x and 64x
speeds.
When the disks where spun over approx 28k rpms the CDs exploded
in small bits penetreating protection sheets made of 3 mm metal (alu).
A disc reinforced with kevlarwire did reach about 30k rpms but after that
it also 
exploded into small bits. The kevlar wire caused so much air resistance so
the
disc used 300W power just to get up to that speed.

So how can the manufacturers  claim 64x speed? The thing is that the
player only 
reaches 64x normal speed compared to the slowest normal speed. They never
speed 
up any more than that. So at the end of a disc a 64x reader only reaches
about 25x
speed. Still faster than my old 2x reader though...

---Per