Beware The Big Bang

[pks1702]

Seems it has escaped

http://www.bbc.co.uk/news/uk-england-essex-14172966

[Jim]

There will be a big bang when they detonate that one

[pks1702]

Fantastic!

'Black' humour at its best.

[senator]

forgive my ignorance on this but were the mines not supposed to go off on impact to stop U boats? If so they weren't very good were they if a dredger can pick them up.

Do many of these things go bang when the dredger finds them?

[Jim]

I've never heard of any incidents Ian although Rod may have heard more. I have involvement at the site end of where dredged materials are discharged and as far as I know, none of the devices that are unloaded have ever gone off on site or in the holds of boats. They have all installed magnets to catch all metal objects including unexploded ordnance before they reach the processing plant.

[Guest]

Surely spending so much time underwater would result in the gun powder being damp..... thus no "bang"?

[pks1702]

As a youngster living right on the North Kent Coast I used to lay in bed imagining this going up.........

http://www.dft.gov.uk/mca/mcga07-home/e ... gomery.htm

Good job we lived in a house and not a bungalow

What was more amazing was that a local attraction was trips round 'the wreck' on the Silver Star getting almost touching distance from it.

[Guest]

As a youngster living right on the North Kent Coast I used to lay in bed imagining this going up.........

http://www.dft.gov.uk/mca/mcga07-home/e ... gomery.htm

Good job we lived in a house and not a bungalow

What was more amazing was that a local attraction was trips round 'the wreck' on the Silver Star getting almost touching distance from it.

And It's still there. I used to live just down the road from it. Thankfully we are now a few miles away from it. I'm sure it will go one day.

There are so many huge container ships and car boats go past it along that channel it makes you cringe. They do say if it goes it will cause a huge tidal wave that will reach as far as London.

[goodall_m1]

forgive my ignorance on this but were the mines not supposed to go off on impact to stop U boats? If so they weren't very good were they if a dredger can pick them up.

As this one was a 2000lb GERMAN mine it was unlikely to be intended to stop U boats...

I would ask Dad, the family expert, but he spent his WW2 mine-sweeping time down in the engine room, keeping a sweeper plugging up and down the East Coast, and not getting too involved with the theory side.

I only know of three firing systems used for mines in WW2, contact (the traditional mine with the horns on it, bump a horn and up she goes), magnetic (detected a steel hull passing near it) and acoustic (listened for certain sound signatures, e.g. a reasonably large ship passing near it). Magnetic and acoustic mines didn't need to floating where a ship could bump into them and hence could lie on the sea-bed and wait so they didn't have cables to drag for.

Most mines were built to fail-safe after a period of time (and after all these are over 60 years old now)

but even if the firing circuit is dead you still have about 3/4 of a ton of explosive lying around

which could theoretically be triggered (and are you sure that the firing circuit is actually dead...)

WW2 minesweeping usually involved either cutting the anchor cables of moored (contact mines) or using various techniques to cause the other mines to trigger themselves, hopefully at a "safe" distance from the sweeper, e.g. towing a large cable with an electric current in it between two boats (the current created a magnetic field big enough to set of magnetic mines). Acoustic mines were tackled using a device like a road jack-hammer designed to make enough noise to trigger them at a distance.

The problems came when you triggered one far enough from your sweeper, but too close to another boat that wasn't equipped for that variety, or found that they had mixed them up and you triggered one of a type that you weren't sweeping for.

In addition to that the sweepers were plodding along in formation in daylight and ideal targets for any Luftwaffe pilots with some spare ammunition or bombs. It was the Luftwaffe that got Dad out of the sweeper, somewhere off the Hull estuary in late 1941 I believe...

The mines that are left may not have activated when dropped (i.e. that may be why the sweepers missed them) , or have "failed safe" but the explosive is likely to be still viable.

So whilst they usually won't go off on their own the safest way to make them really safe is to stick a demolition charge of "plastic" on it, plug in a detonator, and withdraw to a safe distance before triggering it.

The size of the boom tells you if the internal explosive was still viable (it gets triggered by the demolition charge) or had gone "off" and was actually safe.

(There were minefields laid to stop U boats, usually arrays of contact mines set to float below the draft of surface ships, but at a depth where a submerged submarine would bump into them or snag the mine's anchor cable and drag the mine into contact)

[jimbo]

7000 tons Wow! Probably won't go off now, but best left to the Conger Eeels to figure it out

[pks1702]

7000 tons Wow! Probably won't go off now, but best left to the Conger Eeels to figure it out

They managed to get some off there is actually 1400 tonnes on board; Conger Eels flown into Billingsgate if it goes up.

http://www.dft.gov.uk/mca/ops-row-mca_r ... report.pdf

Chances a pretty remote but it has been hit a couple of times by coasters.

I think you will find our pilot passes this on an almost daily basis

[goodall_m1]

The Big Bang has gone BANG (the mine not the SS Richard Montgomery!)

http://www.bbc.co.uk/news/uk-england-essex-14218353

Quite a big bang, so I would say that the explosive in this one was still viable

(either that or Bomb disposal guys used an awful lot of plastic)

[MY littleboat]

..Actually when I saw the footage I thought Ian was just doing a bit of 'on the go' re-fuelling!

[senator]

Wonder what the wash was like off that?

[pks1702]

I think I saw Jimbo's Conger

[MY littleboat]

The 'Big Bangs' that we see when ordnance is blown up is the ordnance used to dispose of it. RDX type of explosive, which is pretty much all that was ever used in those days, is inherintly stable (Unlike many modern explosives which become more and more unstable as they age and deteriorate) but more importantly, extremely suseptible to malfunctioning when damp.

I have some very good friends in the business, one of which was working at LPTA who tested a whole bunch of recovered amunition from underwater storage tests (which are always of course on-going) recently and I'm pleased to say that they worked as well as other British engineered products of the day - these being early 70s vintage - Morris Marina vintage - mainly RDX and early Nitro stuff, and I'm led to believe, had a sub 5% activation rate, and when they did, most partially detonated..

.. so talks of tidal waves washing in to London from the Richard Montgomery are pretty far fetched, and you'll be glad to kn ow, that unless they had some secret stash of German Plastic Explosive on board (As the US didnt have any when the boat sank), I think it's safe to say that the larger concern is the risk to shipping than the imminent self destruction.

Incidentally, regarding mines dropped off the East Anglian coast during the period 1940 to 43 (From the book - Shingle Street Secret) Most are still unaccounted for, sunk through water ingress or were taken as post war 'souvineers' after washing up on our beaches!