Dear Colleagues;
I am doing some research regarding a bomb attack on a Swiss village during WW2. It is reported that several bombs did not explode and therefore the type is exaclty known. It was an American 547 LBS bomb, about 1180mm long (without the wings at the end) and there was a yellow painted ribbon with the inscription ” Comp B” (other bombs expoloded as foreseen).
That’s all fine.
But now I would bei nterested, what effect such bomb actually had. Not the effect on buildings which were directly hit – but buildings further away. In the list of damaged buildings we have such which were 250 up to 400 meters away and the onwers are still claiming broken windowas and damage to the tiled roofs.
Is it realistic that such damage occured in such a distance?
Appreciate any help. Many thanks in advance 🙂
By: Kuno - 16th February 2016 at 23:13
Thank you very much for all those very valuable pieces of information.
By: Arabella-Cox - 16th February 2016 at 21:45
The results of any bomb exploding is widely different depending on the casing design and whether the bomb exploded directly on contact with the surface or penetrated the ground. In the latter case most of the blast is directed upwards. For the destruction of “soft” targets instantaneous fusing is used to direct the blast along the earth’s surface.
Conventional bombs were usually used where penetration of the target was required. Light-case designs, such as land mines and cookies were designed especially for the purpose of demolishing built-up areas. They hardly penetrated the ground and exploded on contact with the surface.
Anon.
By: Lazy8 - 16th February 2016 at 20:11
I’m sure there are others with more detailed knowledge than I – my knowledge of such matters comes from living in a house that had been damaged by a bomb falling at a similar distance to that you describe. 30 years later I was able to observe the evidence. Until someone else can explain it better, here’s my thoughts:
Windows are broken because a force is applied to the glass which takes it beyond it’s elastic limit – glass can flex a bit, but once you get past the limit it cracks or shatters. When a bomb falls nearby there is an overpressure which can shatter the whole pane. If you are far enough away that that pressure is insufficient to break or crack the glass you still have to worry about the effects of debris thrown up by the blast. Small items thrown by the blast can apply a point force to a pane of glass which will break it just as easily as an overpressure takes out the whole window. That doesn’t need explaining, does it – think child’s ball through neighbour’s window… So it’s just a question of maths: move a mass of air over a given distance with sufficient force to break the glass and you have to cover the entire area; move a small stone with similar force and because it’s so much further it will clearly potentially go further.
Roof tiles are made, and the way they are hung is designed to absorb downforces from rain and sideways forces from wind. Those forces press the tiles on to each other and the whole roof helps to support itself. When you have bombs going off at aground level that provides an upforce. Tiles do not handle that well at all, as it makes them all behave individually. It tends to snap off the little lugs on the back that keep the tiles in position relative to their neighbours, so they slide around. If you have tiles without the lugs, such as slates, they will have been nailed in place, and the upforce can break either the nail or the hole it’s gone through, with the same effect. Moving tiles lets water in, lets wind in to move the tiles further, and so on.
As for distances, I think it depends a lot on the local topology, precisely where the bomb went off in relation to the building and other local features, and even the weather at the time. As I mentioned, the house I lived in in the 1970s was about 250-300 metres from a bomb site where another house had been completely demolished. We had a big picture window, with a metal frame, at the front – so would have been pretty well edge-on to the blast – which was bowed in by several inches as a result. I can’t imagine there was much glass left intact by that sort of movement. Sadly I haven’t the faintest idea what sort of bomb, nor how many of them, did the damage.
By: Kuno - 16th February 2016 at 19:32
Any good? Yes, very good. However, can I interprete “visible damage” as damage to walls etc – windows may be blast at a further distance?
By: TonyT - 16th February 2016 at 19:26
Any good?
http://www.bocn.co.uk/vbforum/threads/86833-Anyone-know-the-blast-radius-of-a-WW2-500lb-MC-Bomb
By: Mahone - 16th February 2016 at 19:25
Well it might not be the most academic of studies: but you could try “Blitz Street” – a TV programme made a few years ago to examine the effects of bombing in London…. Part one covers 250 and 500lb bombs – as below.
Sign In
February 16, 2016 at 7:05 pm