On Fri, 6 Jun 2008 01:39:51 -0700 (PDT) someone who may be Mizter T
wrote this:-

Rather than saying the bomb had started ticketing I suspect more
accurate way of describing it is to say that the fuse appeared to have
been armed / activated. I'm afraid I'm not much of an expert in
unexploded ordinance so whilst it did sound rather odd for all I know
the bomb was/is actually ticking.

It could have started ticking as they approached it, though I
suspect this is a bit of journalistic hyperbole. Apart from anything
else, how would they know whether it was ticking or not before they
approached it? Is the cat alive or dead inside the box before one
opens it?

Some bombs of that era were equipped with mechanical timer
mechanisms, the common phrase for them being a delayed action bomb,
amongst other fuzes. IIRC these were started by the impact of the
bomb hitting something, if they failed to start then hitting the
bomb with something or jolting it could start the mechanism. They
could be heard ticking with a stethoscope and, if the mechanism
contained magnetisable parts, discouraged from ticking with a
magnetic clock-stopper.

I think corrosion would have had an effect on the mechanism since it
was dropped. However, corrosion would have affected all fuzing
mechanisms and possibly made them more unstable than in the 1940s,
though it is equally possible that corrosion has made them more
stable and would prevent the bomb exploding. It all depends on the
materials used and due to shortages the Germans used some
undesirable materials at times (for example steel cartridge cases
rather than brass).

The best approach is presumably to blow the thing up in situ, but
where this is not possible (for example this would damage things
surrounding the bomb) then just disrupt the fuzes to prevent them
activating if they are still capable of doing so and then move the
(now rather less dangerous) bomb somewhere suitable to blow it up.
The bomb disposal people have favourite places to take things to
blow them up. A few years ago I arrived at an old fort just as the
Royal Navy were leaving after they had blown some things up in a
secluded location, which was perhaps chosen partly because the sound
would not be heard on land due to the surrounding cliffs/hills.



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54