Not that it's either here nor there, but I don't think that at normal temps, the difference between the expansion rate of stamp metal and whatever plastic they make CDs from differs that much.
I think it's as much the fact that a plastic CD case's spindle-holder is made of plastic that bows in when you push on the CD, then pops back out so that a little lip on each tine of the spindle-thingie keeps the CD in place. There is little or no outward force on the hole in the CD. The stamp metal cases don't have any give -- the metal flange that the hole in the CD fits over is a very tight fit, and the plastic of the CD is under tension. I suspect the CD gradually cracks over time to reduce the pressure, or if you drop the case, forces in the plane of the CD stress the CD until it cracks. Sorry, it's Friday, and I worked for a mechanical engineering firm for ten years, so I can blather on about mechanical design all day. Complaining about the crappiness of CD cases was a popular work time-waster. Though one engineer had a good point -- when you drop a CD case, the case often breaks but the CD does not. The thin, bendable parts of the CD case absorbs force and breaks rather than transmitting the force to the CD. It's the same reason the battery and front bezel of a lot of cell phones pop off if you drop the phone -- they channel a lot of the impact force into falling apart instead of imparting all sorts of torsion and shear to the display and circuit board inside. On Fri, Apr 18, 2008 at 3:26 PM, Michael Kuszynski <[EMAIL PROTECTED]> wrote: > yea right. as if i was supposed to believe that. pfff... > > > > On 4/18/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > The plastic of the disc will not expand and contract like the metal stub on > > which it rests in the case; over time, as it gets warm and expands, the > > discs crack from the center outward . > > > > jeff > > > > > > -------------- Original message ---------------------- > > From: "Frank Glazer" <[EMAIL PROTECTED]> > > > as i'm not the owner of any chain reaction tin case CDs i'm a bit out > > > of the loop. what was it about the design of those cases that wreaked > > > havoc upon the discs? > > > > > > > > -- > --- > Michael Kuszynski > [EMAIL PROTECTED] > [EMAIL PROTECTED] > http://www.planerecordings.com > New York, NY >
