Destruction in a Good Cause....!

In December 2004, I gave a demo of the Destruct-o-tron at the Christmas dorkbotlondon meeting. (The Destruct-o-tron is a large bank of capacitors which can discharge an immense amount of electrical energy very quickly).
A few days previously, Dave Green of NTK had suggested that the event might be a good opportunity to contribute to the Band Aid Dilemma project by destroying a couple of Band Aid 20 CDs in interesting ways....

Dave with the first 'victim'...

Ready for launch. The CD is sitting on an aluminium disc (ex hard-drive platter), on top of a CD case cover, on a coil of 5 turns of 6mm² wire (the CD case is just to ensure the platter is sitting on top of the coil, not inside it.

As this was a semi-public affair, some containment was in order - a short length of ten inch polythene gas pipe, with a thick MDF insert in the top. A Perspex sheet protects against the occasional disintegrating cable and escaping CD shrapnel fragments.

Ready to fire..

BANG...... Approximately 1.5 kilojoules of energy is dumped into the coil. This creates a massive magnetic field, which in turns induces a huge electrical current in the disc, generating an opposing magnetic field, and the resulting force provides a very large acceleration of the disc away from the coil.
The Hard-Disc platter impacts against the CD and accelerates it from 0 to about 150 miles per hour in 1/1000th of a second, smashing it into many small fragments.
If you want to get an idea of what actually happened, check out the High-speed camera movies and frame sequences on this page

Well that was fun, but we still had one CD left... In a flash of inspiration, I decided that it might be fun to fire the second CD while still in its slim jewel case. This was based on the theory that more plastic = more debris = more fun. However the resulting devastation was so much more than that....
I also thought that having the CD & case hit something sharper than the top of the containment vessel might help with the disintegration, so I fixed a wooden wedge to the top using Blu-Tak.

On removing the containment tube, apart from many, many small bits of broken CD and case, we were greeted by the sight of the cardboard inlay impaled on the spike, in a way I'm sure we couldn't have repeated if we'd actually been trying to do it...!  

Some of the debris....