Rich said:
Forgive my ignorance, but how do you blow up a CD with a Dremel?
Thanks,
Rich
Aha! odds on if you google it (i'm too lazy
you'll find some nice
mpegs. If you have the dremel sander attachment (a 10mm dia or so
cylinder of rubber, about 10mm high around which a ring of sandpaper
sits), that just happens to fit nicely into the hole in the centre of a
CD (a slight interference fit). Crank it up... I suggest doing a little
bit at a time, and using your thumb to push the CD off the dremel. A
wall and a ramp allow you to make the cd spin in large loops - floor,
ramp, door, ceiling etc - the ramp shoots it backwards, but the rotation
makes it go forwards when it hits the ground. Each time it does the CD
gets damaged, and eventually flies to bits. I had a CD running at full
speed on my dremel without it bursting, but several did. Wear heavy
clothing, gloves and face protection. And ensure (not insure - grr)
no-one comes into the room while you do it. If I wasnt so lazy I'd
calculate the energy stored in the CD....oh OK, J=0.5M*(Ro^2+Ri^2)
Ro = 120mm, Ri = 15mm, t = 1.2mm so volume
V = 3.14*(120mm^2-15mm^2)*1.2mm = 53.44e-6 m^3. the CD is basically
polycarbonate, density Rho = 1.2g/cm^3 = 1200kg/m^3. sanity check:
density of aluminium = 2700kg/m^3, glass = 2600kg/m^3 so sounds OK.
M = V*Rho = 53.44e-6*1200 = 64g = 0.14lb (exactly what some of the DCD
shipping stuff I googled said)
J = 0.5*0.064*(120mm^2+15mm^2) = 468e-6 - agrees exactly with
http://hyperphysics.phy-astr.gsu.edu/hbase/ihoop.html#ihoop2
max speed = 35,000 rpm = 583.33Hz = 3665rad/s
Emax = 0.5*J*w^2 = 3kJ
**** with this at your peril. 3kJ is enough to cause a serious injury. I
have been in close proximity to a 17kJ bang (a large inverter shat
itself while I stood beside it) and that was scary. but nothing like the
1MJ flywheel that shat itself when Stan and I were testing it
(thankfully it had a 2" Al containment vessel, securey bolted to a very
heavy plate). At a spin test for the same product, we made it fail
catastrophically by overspeeding it with a uqill shaft - died at 7.2MJ,
inside a spin pit. and melted $6,000 worth of lead bricks. man did the
building shake.
you have been warned.
cheers
Terry
