Cave - Bullethöhle

Fri 16 Jul 1999
Duncan Collis

Strolled out across the plateau to find a hole I noted last year, which rattled for a while when stones were lobbed down it, but which was constricted at the top. Went armed with drill & hilti caps, intending to alleviate the constriction slightly. The method is simple: drill an 8mm hole about 10 cm deep, poke a cap in and insert the firing pin (a bit of 8mm threaded bar cut to a chisel tip), put something in place to stop shrapnel from flying out (a carrymat in this case), and tonk the firing pin with a hammer until the cap goes off and splits the rock.

People always ask: "why doesn't the cap just blow the firing pin straight back out of the hole ?". The answer is that the momentum of the hammer is sufficient to stop it. And it always works. I've probably set off about 30 caps before, and have been present when numerous others have been detonated. The result is always the same: the rock falls apart, and the firing pin doesn't shoot off out of the hole.

First cap: Firing pin popped out of the hole. Didn't drop down shaft because it was tied to my wrist with a bit of string. Rock unscathed.

Second cap: ditto

Third cap: Firing pin went into reverse and fucked off at about 500 miles an hour, rock unscathed. Fortunately, the string holding it to my wrist snapped, or it would have gone in a circle and straight through my back. As it was, it simply reddened the skin of my wrist a bit.

Fourth cap (different hole): Chipped off very small chunk of rock. Then we went back to TC as it was raining.

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