I just started reading Frederick Forsythe’s “The Fourth Protocol”, and there’s a scene where a character has to break into a safe. He uses something called CLC, “charge linear cutting”, which is said to be a v-shape strip of explosive, which is apparently the best way to cut through metal.
I can have a rough guess at how it could work, but I’m wondering if anyone does/has use(d) CLC, and could explain please!
Thanks
Harry
cross sectional shape:
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This is a shaped charge intended to cut a line rather that merely punch a hole (handled these in our “inert” magazine in USMC).
Try looking up “linear charge” or “primacord” for more specifics. Linear charges are used in aerospace applications for slicing a series of bolts all simultaneously, or making a precise and instantaneous cut in a piece of metal. Examples include separating the payload shroud from a space launch vehicle, or perforating the interstage for stage separation.
You’ve basically got it right: it’s a piece of explosive, similar to TNT, in rope or cable form. I’ll plead ignorance on the “shaping” aspect, but here are some sources to get you started in your hunt.
This article gives a pretty good rule-of-thumb estimate of how powerful it is; the expert cited claims a one-foot length would take his arm off above the elbow if it were lit in his hand.
These guys seem to know about the V-shape element you’re asking about. For what it’s worth, I got it by googling “shaped charge” and “V-shaped”.
Enjoy. And don’t ask for this stuff for X-mas… you’ll shoot your eye out.
The person giving that rule of thumb argument didn’t know what they were talking about, and freely admitted it. I suspect that they oversimplified or misinterpreted what the expert said.
Primacord is a high-velocity explosive, true, A 1-ft length, wrapped around an arm by an expert might blow an arm off if properly detonated, but I’m a bit skeptical, because 1 ft of prima cord contains just a few grams of actual explosive. (I usually worked with primacord with a charge load of 7.5g/meter to 25g/m, and a foot is 0.3m. It definitely won’t blow off an arm if “ignited” (as the article claimed) - a mistake no expert would ever. Primacord is often used as an ignitable fuse!
I’ve lit it hundreds of times, with nary a pop. For goodness sake, you used to be able to buy low grade primacord in hobby shops!
Primacord is a thin string of explosive, usually wrapped in a woven and/or sealed plastic covering. When ignited, it burns at a rapid rate, and as such, is good for timing ignitions (equal lengths to the inch gave simultaneous explosions to within milliseconds). It can also be detonated with a primer or cap; the detonation proceeds down the line at extremely high velocity (on the rough order of 20,000 ft/second) which allows for extremely high precision timing, especially since a properly rigged primacord knot may not require a secondary detonator: since it is a detonation, not a flame, it can generate enough shock wave to detonate some other explosives.
“a mistake no expert would ever” make.
I really should have this premature detonation problem looked at.
OK… how shaped charges work…
Take a coffee can and fill it with plastic explosive. (This will be a cylindrical shaped charge, it will help explain a linear one.) Take a champagne bottle use the pointy end to make a cavity in open end of the can, that is shape the explosives into a cone-like cavity.
Place a detonator at the other end of the can. Set off the the explosion and look really carefully. This happens really fast. The explosion consumes (or “burns”) the explosive in a disc (OK, a semi-sphere) centered on the detonator. It burns evenly in a predictable matter.
Until it gets to the cavity. The explosion travels faster in the air than in the explosive itself. The force of the explosion wants the fastest way out to equalize pressure. A large part of the force of the explosion is directed into the cavity and so to the target.
A shaped charge simply is a kind of lens to focus explosive energy.
Fantastic, cheers people, I kinda had an inkling of what it could be, but I wanted to know because I have to try and know everything!
Thanks for the links, Jurph, I’m checking them out now. Thanks, KP, your experience with the stuff seems cool, I just wish I had a chance to check some out in first person, too, along with most people with a ‘y’ chromosone.
Paul in Saudi, is plastic explosive widely availiable in Saudi Arabia? If I tried that experiment here (South-West England), I’m pretty sure I’d have some explaining to do to the authorities.
Thanks everyone,
Cheers
Harry
Yup, when I was being trained for it, I was warned that I could suffer “very chafed wrists” fro using it in civilian life without a permit…
Drat…