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Investigating Angular Velocity
mbreitba writes "Sam Barros is at it again, Some may know him for his Railgun research, and some may know him for his homemade cannons. But now he's found a use for all those old CD's you don't need anymore. Personally, I couldn't think of a better use for them."
turns out most cds explode at 28k rpm according to this story from a couple years back. and even then it was a dupe.
... or put 'em in the microwave for a couple of seconds, shiny side up. Put a sheet of paper below if you don't want to stain the glass plate.
Trollem mirabilem hanc subnotationis exigiutas non caperet
This is a dupe of thiswhich was a dupe, funny that. Here is a mirror of it (the first dupe), since the site was taken down: My Mirror
Your hair look like poop, Bob! - Wanker.
Already been done. The first 52X CD-ROM drives (from Kenwood, as I recall) used multiple read heads to get 52X equivalent speed.
For us mere mortals, not even that is possible... He seems to be slashdotted already...
But according to this (another slashdot comment), you have violated his notice (removing any material), if you were planning on displaying it (doesn't say anything about public showing), so I GUESS YOU'RE SCREWED (or not):
Copyright © 2002 by Sam Barros. All rights reserved. Removing any material from this site for display without consent from its author consists in an infringement of international copyright laws and can result in fines up to $50000 per infringement, plus legal costs. So ASK ME before you remove anything from here.
*Goes check the http://www.thedarkcitadel.com/cd/ mirror that someone else kindly posted*
Have you ever loaded a faulty CD into a high speed (30X or higher) CD-ROM player, heard it spin up to incredible speeds, rattling and whining, and thought to yourself: "this thing is going to explode"? When CDs came out they were heralded as the solution for the need for high storage-high speed information devices, transferring data at a whopping 150kb/s, but like all technologies, 1x CD players quickly became obsolete as the need for higher and higher transfer rates pushed for faster players, and, with them, higher rotational speeds. As we advance into the 21st century CD players are reaching the ultimate speed limit: we are getting to the point where the CD player simply can not spin the CD any faster or else the CD will literally fly apart. On the interests of the advancement of high speed computing PowerLabs brings to you:
THE ULTIMATE CD SPEED LIMIT!
WARNING: This page is written for amusement only: These experiments are VERY hazardous!; A high speed rotating CD Rom is a bomb ready to explode and will send razor sharp plastic shrapnel in all directions when least expected. DO not attempt to replicate any of the experiments described below!
Setup:
Before an experiment could be devised where a CD would be rotated to complete failure, a proper motor had to be obtained that would be capable of achieving those high rotational velocities with the load presented by a CD. Although a CD is very light and aerodynamic, when it starts to spin at a couple tens of thousandths of rotations per minute the drag created by air around its surface can be to slow the motor down considerably. High torque motors are very common and cheap, as are small high speed motors. Unfortunately however, high speed, high torque motors are a much rarer and expensive find.
My choice was to use a Dremel tool as the motor. It was cheap, easily available, and, more importantly, the rated 35000RPM spindle speed meant that it had some real potential for spinning things to destruction.
At 35000RPM very small imperfections and balancing errors can lead to extreme vibration; so much, in fact, that it would be possible to damage the bearings or bend the axle on the tool if something as heavy as a CD was to start wobbling (bear in mind that the Dremel tool was designed for very small, light weight loads and even then many of its attachments carry warnings not to be used at full speed). One of the first challenges of the research was to find a means to secure the CD perfectly in the middle of the tool. A custom made CNC lathe spun aluminum holder was considered but before I ever left the room I realized that the cylindrical sanding attachments Dremel makes not only fit a CD hole perfectly, but also have adjustable width so that the CD could be gripped in place. With the CD in place and the dremel plugged in, it was time for the fun to begin!
The Dremel was switched on and the rotational velocity was gradually increased to its maximum, at which point the CD hummed and whined in a very menacing manner. Mildly disappointed that it had not exploded, I realized that it wanted out; a quick jerk at the tool and the CD slid out of the holder and contacted the carpet whilst spinning at ungodly speeds. It peeled out a bit in front of me and proceeded to make its way to the door at a very high speed. On contacting the closed door, the CD did a most unexpected thing: it first bounced back a few inches, and then, when it hit the door again, it jumped straight up the door and struck the ceiling, exploding into thousands of fragments which rained down on the entire room. This first experiment was unfortunately not videoed, but it served to get everyone in the room to put glasses on and cower away behind pieces of furniture, whilst people in the hall corridor quickly made their way to my door to ask what was going on. Now, with an audience, the camera was taken out and the real experimentation began...
ÂA standard compact disk has a diameter of 12cm. If this disk is to spin at 35000RPM, th
You can't actually read or write at 48x speed anyway, except with a perfectly flawless disc (no tiny, near-invisible scratches, absolutely centered and balanced, no thickness or density variations) anyway. And if you could, the data rate would be starting to push the limit of what IDE can do (or indeed SCSI).
How temperature affects the properties of a material are intrinsic to the material. Examples: Water becomes more rigid when you freeze it. Silly Puddy becomes hard when you freeze it. But with plastics, yes they generally lose their ability to bend without breaking. It raises their resistance to change, which raises the stress in the material at a given amount of bending. That leads to it breaking.
P
Humans are slow, innaccurate, and brilliant; computers are fast, acurrate, and dumb; together they are unbeatable
Well I doubt the wavelength the scanner uses matches the CD. Note that there aren't any real black pits on the CD. Only a reflective layer, and a semi reflective layer with a distance of exactly lambda/4. Now when the laser in a classical cd player "looks" at the cd where the semi reflective layer has a "pit" it gets reflected as whole on the reflective layer. If there is not a pit, half of the light gets reflected, half passes through gets reflected on the second layer, goes back and gosh it interferes destructive with the light that got reflected on the first layer. Thats why wave length and distance between the layers need to match each other.
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Karma 50, and all I got was this lousy T-Shirt.
Will not function likely with a standard scanner since the wavelength do not match, just have explained that.
h ol d=0&commentsort=3&tid=137&mode=thread&pid=6168826# 6169070
http://slashdot.org/comments.pl?sid=67125&thres
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Karma 50, and all I got was this lousy T-Shirt.
Exactly! Thats the technical explanation.
:o)
The explanation with scattering pits, and focus are for the masses who do not know what destructive interefence is
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Karma 50, and all I got was this lousy T-Shirt.
You will also get a lot of really smelly fumes from the ignition.
I have no idea of the toxicity of these fumes, but I can tell you your pizza will taste funny the next time you use the microwave oven to prepare it.
So, if you wanna experiment, do it in someone else's oven.
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
and the winner of the 'pedantic of the year' award is ...
42
Unable to resist...
Ye olde "9 pregnant women having a baby in 1 month" argument... For another analogue that may apply here, it's worth noting that recent developments in semiconductor processing technology includes a move to 30cm wafers, specifically to accommodate parallelism in production.
I don't remember the dates specifically, but silicon production "began" with 3-inch wafers, then transitioned to 5-inch, then 8-inch. So, don't be too harsh on those who suggest doing things in parallel.
Producing 1000 CDs per day? Consider standard pressing techniques, which is nearly as flexible as "burning" CDs but way cheaper and can be performed as quickly as you wish. (Did you know that CD sputtering chambers can contain multiple different blanks?)
The secret to carving CDs is to go slow and insure the rigidity of the CD.I find that by using contact cement and gluing a piece of 1/8" plywood to the BOTTOM of the CD, I can use a band saw on a CD quite well. The wood prevents the CD from bending, which will cause it to catch and crack/shatter or chip. I've also found grinding wheels to work well, too ... but the same thing, you need to attach something rigid to prevent the CD from bending. I find plexiglass to work well, too.
-Ab
Nothing fails quite like prayer.
It's not circumference times the rotational velocity. It's the RADIUS times the rotational velocity.
.06 m x 583.3 rotations / second (using his numbers) = 34.998 m/s = 114.8 fps = 78.3 mph.
So, for the standard CD thats:
If it really was going 220 m/s, that's a significant fraction of the speed of sound at sea level (340 m/s).