2001-08-15 19:29:27 +01:00
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<title>CUCC Expo Handbook: rigging - artificial belays - bolts</title>
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<center><h2>Bolt belays - placing and using</h2></center>
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<p>Most people on Austria expeditions will be familiar with the use of bolt
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belays from trips in the UK. In Austria, caves already explored will have
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bolts with the hangers removed, which can be quite hard to spot. Anyone
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hoping for a join-the-dots trip will be disappointed. These bolts can usually
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be found fairly easily by anyone familiar with expo rigging, <i>provided a
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good rigging guide was drawn up by the previous explorers</i>. Y-hangs are
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common at pitch heads, so check that you find both bolts. Lower down, it is
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as well to know whether a bolt has been placed for a rebelay or a deviation,
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as it may not become obvious which until some way down the pitch. Such a
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rigging guide is also useful to show which existing bolts should <b>not</b>
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be used. Inevitably some bolts will be badly placed, or may become damaged.
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It is as important not to use these as it is to find the right ones.
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<p>For new pitches when, as is often the case, good natural belays are
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scarce, you must place one or more bolts yourself. Doing so puts you in
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a position of responsibility both for the safety of future users of that
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bolt and for the conservation of the cave. The aim should always be to
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put in good bolts which will contribute to a safe rig with a minimum of
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further bolting needed.
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<p>This is easier said than done, and there is ample evidence of this in
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caves CUCC have explored over the years. The best place for a bolt may
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be far from obvious until the pitch has been descended. Or maybe the best
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place is obvious, but that place is hard to reach. It is tempting to try
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to reach for the best placement, but overstretching or an insecure perch
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may lead to a poor bolt in the perfect place. This is very much to be
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avoided, since it is now impossible to put a good bolt in the perfect
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place - the rock around the first placement will have been stressed and
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another bolt should not be placed closer than about 20 cm from it.
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<h3>Placing bolts</h3>
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<p>Placing a bolt is a simple matter of drilling a hole and inserting a rock
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anchor. The bottom end of the rock anchor is expanded by some mechanism,
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and thus grips tightly in the hole, resisting any attempt to pull it
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out. The anchor is strongest if loaded at right angles to its axis, ie.
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parallel with the rock surface. Hence for a vertical pitch, it is normally
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best to place the anchor in a vertical rock surface.
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<p>The hole may be made in either of two ways. For the penalty of carrying
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considerable extra weight, a cordless power drill is the quickest way to
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drill the hole. The heaviest item is the drill battery, which must, of
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course, be removed from the cave each time it needs charging. This method is
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of the most use where a lot of bolts need to be placed on a pitch series
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relatively accessible from an entrance. Lots of bolts are also needed for
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climbs up or exposed traverses to reach inaccessible passages.
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<p><center><a href="../../smkridge/161/l/boltin.htm"><img alt="(36k image)"
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src="../../smkridge/161/t/boltin.jpg" width=113 height=152></a>
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<a href="../l/bosch.htm"><img alt="(73k image)"
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src="../t/bosch.jpg" width=200 height=200></a><br>
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<b>Bolting by Hand Using the Drill</b></center>
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<p>The older (and more reliable, but slower) method is to use the anchor
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itself as the drill bit, driven in by use of a hammer. 8mm self-drilling
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rock anchors have teeth around their bottom for this purpose. The anchor is
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attached to a bolt driver, which is then repeatedly pounded with a hammer,
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whilst rotating the anchor by hand every couple of whacks. When this gets
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a little stiff, the anchor is pulled out of its hole and the dust and rock
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chips blown out. The process is repeated until the top of the anchor is
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just below the rock surface. A small conical "wedge" is then inserted into
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end of the anchor (thin end into the anchor) and the pair put back in the
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hole. Three or four good hard whacks with the hammer "set" the anchor by
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driving the wedge into the bottom end, expanding it. Beware of hitting it too
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many times, as this will start to weaken the rock around the anchor.
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<p>The hole produced by the power drill is a different shape from that
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produced by hand - since the power drill bit has a pointed end. It is also quite difficult to get the depth of the hole exactly right. For this
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reason, if a self-drilling anchor is set into a powerdrill hole, the wedge
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will not be driven into the anchor and an unsafe placement will result.
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To use a self-drilling anchor, it is best to under-drill the hole, and
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finish off to just the right depth, and a square hole-bottom with a hand
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driver.
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<p>More efficiently for power-drilled holes, use a form of anchor specially
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intended for these holes. These anchors use a smaller hole, so you get more
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holes for your money from one battery charge, and the design of anchor means
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that the bottom of the hole is not used in the setting process, and the depth
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of the hole is therefore less critical (as long as it is deep enough that the
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anchor goes right in !)
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<p><center><a href="../../years/1990/hilti1-300.png"><img
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alt="before setting - 1k png" width=530 height=90 hspace=10 vspace=10
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src="../../years/1990/hilti1-100.png"></a><br>
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<b>Hilti HDK spits before and after setting.</b><br>
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<a href="../../years/1990/hilti2-300.png"><img alt="after setting - 1k png"
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width=220 height=94 hspace=10 vspace=10
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src="../../years/1990/hilti2-100.png"></a></center>
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<hr>
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<!-- LINKS -->
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2001-08-16 13:43:09 +01:00
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2001-08-15 19:29:27 +01:00
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<a href="../index.htm">Expedition Handbook</a> - Intro<br>
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2001-08-15 19:29:27 +01:00
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