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Establishing the Maximum Speed of a CD-ROM Drive
UnknownSoldier writes "Ever wondered how fast CD-ROM drives can spin their CDs before the CD will self destruct due to centrifugal force? This person was too, and has his results. (So much for those 100x drives)."
The google cache for this page is here
32x might be exxagerating a little, but I know my 50x sounds like a jet engine taking off when it spins up.
Future drives will have to take advantage of technologies like TrueX to be tolerable.
Then again, how fast do I really need my CD-ROM to be? I mean, I only use my CD-ROM to 1) reinstall the system and 2) to play music. A 32x CD-ROM is plenty fast to accomplish both of these tasks.
The point of this experiment wasn't to push technology but to do something silly to wow your geek friends. (Then again, I didn't read the link since it was Slashdotted after a measely 6 posts).
What i'm waiting for..
are scratch-resistant CD's. or CD's you can pull the outer layer off of to reveal a new shiny surface. I treat my burnt cd's like shite, so its my own fault.. but still.
what isn't my fault is old cd's who's upper reflective layer begins to flake off.. cheap sons of bitches made in 1997 just arent sufficent. I lost my entire backup of por..err, my 600mb hard disk.
You probably already know this, but just for the record -- unless you have a defective CD drive, it shouldn't ever try to spin an audio disc up to full speed unless you're doing digital audio extraction. If you're merely listening to your CD, it will spin at 1X, just like any standard CD audio player.
Kenwood made a drive that does this. It spins at around 10x and reads at 72x. Unfortunately, they have discontinued it.
Donate background CPU time to fight cancer.
This one has no broken images.
I would bet that it's cheaper and more practical to shrink the bits. This seems to have worked well for DVD.
Donate background CPU time to fight cancer.
Most (all?) CD-ROM drives over 32X already use multiple lasers to read multiple tracks at once. They usually say "multi-read" on the boxes if they use this technology. Zen research (http://www.zenresearch.com/) invented this technique, and holds patents relating to it.
Afreey and Infineon already have a 100x (TrueX) CD-Rom drive (25x DVD)", it came out in 2001...
This is the future (but who cares, we'll go solid state before it gets popular).
Imperium et libertas
Autocracy and freedom
Background
The Audio CD Standard was set sometime back in the 70's. Then, it was decided that the record should rotate with different speeds, depending on where on the record the data was read, to get a constant data transfer rate. The method is named CLV (Constant Linear Velocity), or constant transfer rate. The transfer rate of an audio CD is a mere 176 kB/s, and to reach this rate the record only has to spin with 530 rpm when reading the innermost track, and 200 rpm for the outer track.
CAV is for Whimps
To be able to publish ever increasing spin ratios, many manufacturers have resorted to CAV (Constant Angular Velocity), a method whereby the record is not rotated faster when reading inner tracks. Thus they can specify impressive spin ratios for outer tracks and sell more, but in reality the spin ratio for the inner tracks is only 37.7% of this value.
CLV is for the Tough Boys
A 64x drive using CLV would have to rotate the disc with 33,920 rpm when reading an inner track, exposing the hub of the disk to a tangential force of some 45 N/mm2. A point on the periphery of the disc will be moving with 213 metres per second, slightly more than half the speed of sound. Can the disc take that?
The answer is no. A powerful no.
At about 52x, i.e. 27,500 rpm, most manufacturer's CDs blew up in a rain of plastic particles, leaving their marks on the premises. The result was a pile of shimmering plastic chips.
He also tried Kevlar reinforcement
In our efforts of reaching ever increasing speeds, we tried to reinforce a disc with Kevlar wires. [...] It turned out our motor didn't have enough power to spin up the disc enough to explode it in one try, because the Kevlar wires consumed several hundred watts of motor power for aerobreaking. [photo] After an extended period of time (about 20 seconds) at close to 28,000 rpm, the disc blew up with a loud bang anyway, with the wires remaining on the hub, as shown in the picture. It can be clearly seen that the wires remains pointing radially from the hub. The Kevlar wires had been stretched radially and performed as intended. What made the disc explode, was the creepage of the plastic material, i.e. its stretching over time, subjected to the high g forces.
"It is a greater offense to steal men's labor, than their clothes"
Sorry to be a physics geek here, but there's no such thing as "centrifugal" force, unless you're talking about the force caused by a centrifuge dropped from a height.
There IS "centripetal" force, that refers to the force on an object travelling in a circle, which pushes outward from the axis of said circle on an object while it's travelling about the radius. Say you're spinning a ball on a string around over your head. Your work is translated into acceleration around the axis of the circle as the ball spins around your head, but the force is perpendicular to the path of the ball at any one moment, radiating from the axis. This is proven visually by noting that as you put in more work, spinning the ball faster, the angle from vertical of the string the ball's attached to increases toward 90 degrees. See? Force pushing outward, ball moving in circle. When the string is released though (or the CD breaks up) the ball moves in a straight line matching that along which it was travelling at the moment of release -- momentum then is in action.
To repeat, no centrifugal force. For all our computer learnin', it's surprising that so few paid attention in physics 101.
The only tool you've got against psychosis is experience.
Heh, I figured I'd get either funny or off-topic, wasn't expecting to get 'informative' points.
:) *Watches his Karma roller-coaster*
I honestly meant that as a joke. Seems like every time an article like this shows up on Slashdot, there's always somebody ready to say "whats the point?"
Oh well.
"Derp de derp."
It's called an "acoustic optical modulator", my old company uses them all the time in their laser photographic printers.
We modulate a laser beam on the order of 14 million times a second, actually a lot more than that. Check out www.cymbolic.com (LightJet / PlateJet products).
MadCow.
I used to have a sig, but I set it free and it never came back.
Lithium Niobate Modulaters go at 20 Ghz ( I have one sitting in front of me in a box).
http://www.eospace.com/
Hell they even have a 40 Gb/s, but it isn't that good.
Anyway if you want to redirect the light beam you can use a lithium niobate polarization controller and have polarization dependent componets at the output that only let certain states of light through (and attenuate the rest) and thus you are redirecting the beam down a different waveguide in the ps range.
I am sure there are easier ways. But it is saturday morning....