On 17 Jan 2006 01:42:19 -0800
"Mark Carver" wrote:

Richard A Downing wrote:

On Tue, 17 Jan 2006 00:32:31 GMT
wrote:

On 16 Jan,
"Blueyonder" wrote:


The only evacuated tube commonplace in homes today is the TV
tube, and look at how thick the glass is on the from of that to
withstand the pressure. TV tubes are held together by a strong
metal band just inside the case from the front. If that is
removed, then the whole thing will explode spectacularly (and
will have your eyes out and most of your face off - so don't
even think about experimenting).

ITYM implode.

Probably. There is, however, no practical difference. I've seen
high-speed films of TV tubes imploding (tests for implosion guards
back in the 1960's). The pieces are flung by the inflowing air
into the middle, where some hit one another and bounce back, and
others just keep on going. The net effect is a violent explosion
where bits of glass and the metal bits of the gun are expelled at
high speed. The most dangerous bit is the electron gun that
usually flies straight out the front where a viewer would be!

One of the reasons for the metal band is to direct any implosion - a
bit like a shaped charge for demolition.

TV sets from the 50s and 60s often had a piece of glass (perhaps
perspex ?) in front of the tube, I was always told that was a safety
screen in case of implosion, is that true ?

Yes, that's the 'Implosion Guard' - modern tubes (60's on) have the
implosion guard built in, which, together with the tension band, makes
them much safer. My father worked on the design of them, and
bullet-proof glass, which is why I got to see the films. I'm not an
expert really.

I did come across as a lad in the early 70s a fly tipped TV set, as
any bunch of 11 yr olds would we started to rip it apart, I recall
that had close fitting perspex around the front of the tube. Anybody
know more ? The TV set tipped over, and the tube neck broke off, all
there was was a hissing sound for 10-15 seconds as the air rushed in.
That by the way is the recommended method to 'defuse' a TV tube, I've
done as part of my day job, (wearing goggles and gloves etc, and
using a very long broomhandle)

Most tubes have a small glass 'pip' on the neck somewhere. It's said to
be quite safe to just nip it off with pliers. I don't know if this is
true, and like you, I'd only try it with full protective gear on!!!

R.