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Post by johnt65202 on Dec 10, 2012 22:12:42 GMT
I notice on a lot of Myth busters explosions that when they show the high speed, there is a red streak that runs to the detonator. But, I'm almost sure that they are using electronic detonators so what are we seeing?
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Post by freegan on Dec 10, 2012 22:39:37 GMT
I notice on a lot of Myth busters explosions that when they show the high speed, there is a red streak that runs to the detonator. But, I'm almost sure that they are using electronic detonators so what are we seeing? I'm just guessing but it's probably high speed fuse cord because electronic detonators may be re-usable and best kept remote from the blast if you need to save cash. |
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Post by GTCGreg on Dec 10, 2012 23:37:15 GMT
They use detonation cord. The cord itself sends the detonation "explosion" down its length. The speed of the detonation is around 7,000 meters/second. You can see the "explosion" propagate down the cord in the high speed videos. The cord is only good for one use but is deemed much safer and reliable than other remote detonation systems. en.wikipedia.org/wiki/Detonating_cord |
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Post by the light works on Dec 11, 2012 7:30:40 GMT
I think that is a very impressive demonstration of their high speed cameras.
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Post by silverdragon on Dec 11, 2012 9:54:58 GMT
Det Cord is one-use only, but its so much better, because it always works, and you dont get the "I think there may be some damage in the wires" problem.....
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Post by c64 on Dec 11, 2012 12:49:00 GMT
Det Cord is much cheaper since you need no electric caps. Also Det Cord makes sure all charges blow up with the desired timing. In an electric system, some electric blasting caps get a lot more power than others so there is a high chance that some of them won't ignite.
The alternative is using a digital system with computerized distributor boxes. This is much more versatile and precise in timing but you need to run many long wires to each charge or you blow up your expensive distributors.
And electric wires are not cheaper at all. You can't recycle the parts near the blasting nor the parts the building had fallen on to. And the rest can't be used often since the more often you unroll the wires, the higher the chance that it breaks. So you need a new drum of wires for each blast anyway.
You can't see the current flowing through an electric cable at all. What you see on the show is actual fire in a really fast burning fuse which is made out of explosive powder filled in a semi-transparent plastic hose.
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Post by the light works on Dec 11, 2012 14:56:59 GMT
I think they still use electric caps - but far enough from the explosive that if it fails they can check it without being in the blast radius of the main charge.
maybe in a minimyth they could address the idea that it is so fast that if you stick one end in your ear, and light the other, you cannot pull it out of your ear fast enough to avoid the charge. (using an ear analogue, of course.
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Post by silverdragon on Dec 12, 2012 9:45:07 GMT
I fear that would start something... as in how long a piece of cord would you need to succeed?....
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Post by the light works on Dec 12, 2012 14:42:41 GMT
well, that just takes it to simple math.
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Post by c64 on Dec 12, 2012 16:34:20 GMT
I think they still use electric caps - but far enough from the explosive that if it fails they can check it without being in the blast radius of the main charge. maybe in a minimyth they could address the idea that it is so fast that if you stick one end in your ear, and light the other, you cannot pull it out of your ear fast enough to avoid the charge. (using an ear analogue, of course. Electric caps are still used often. Mainly for simple blast jobs with only one minor charge, computer controlled blasts and especially to start a fire instead of blowing something up. |
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