2001-08-15 19:29:27 +01:00
|
|
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0//EN">
|
2004-05-05 19:39:28 +01:00
|
|
|
<html>
|
2001-08-15 19:29:27 +01:00
|
|
|
<head>
|
2004-05-05 19:39:28 +01:00
|
|
|
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
|
2001-08-15 19:29:27 +01:00
|
|
|
<title>1990: Cambridge Underground report</title>
|
2004-04-21 10:35:34 +01:00
|
|
|
<link rel="stylesheet" type="text/css" href="../../css/main2.css" />
|
2001-08-15 19:29:27 +01:00
|
|
|
</head>
|
|
|
|
|
<body>
|
|
|
|
|
<center><font size=-1>CTS 91.1327/g: Cambridge Underground 1991 pp 32-34</font>
|
|
|
|
|
<h2>Drill Report</h2></center>
|
|
|
|
|
|
|
|
|
|
<p align=right>Wookey
|
|
|
|
|
|
|
|
|
|
<p>As part of this year's techno-overkill we succeeded in getting ourselves
|
|
|
|
|
sponsored by the nice men at Bosch to the tune of one cordless hammer drill.
|
|
|
|
|
This, actually a GBH 24VRE, soon became named Geraldine B. Heronworthy, and
|
|
|
|
|
was affectionately known as just Geraldine.
|
|
|
|
|
|
|
|
|
|
<p>First a bit of spec: the drill has an SDS chuck which allows easy changing
|
|
|
|
|
of bits by hand with no chuck key to lose underground. It comes with a 1.2
|
|
|
|
|
amp hour battery which fits into the handle.
|
|
|
|
|
|
|
|
|
|
<p>The first thing we did was adapt the drill for underground SRT use. We
|
|
|
|
|
added a chain handle with which to hang it from a harness. Tony produced a
|
|
|
|
|
wooden insert to plug in instead of the normal battery which had a curly
|
|
|
|
|
cable attached so that an external battery could be used. Animal's Photon
|
|
|
|
|
Cannon battery was ideal for this as it was 24V and designed to be caveproof
|
|
|
|
|
so a connector for this was fitted. On testing in Settle carpark one weekend
|
|
|
|
|
the drill seemed to go slower than with its own battery but this didn't seem
|
|
|
|
|
likely to be much of a problem. Also a protective baggy was constructed by
|
|
|
|
|
Julian to allow Geraldine to survive the caving experience.
|
|
|
|
|
|
|
|
|
|
<p>In order to test the drill to determine both it and the battery's
|
|
|
|
|
performance we procured a kerbstone from some roadworks and proceeded to
|
|
|
|
|
drill holes in it. This also ensured that the battery had been given its
|
|
|
|
|
first few discharge cycles to get it up to full capacity in accordance with
|
|
|
|
|
Bosch's instructions. True to form the number of holes (30mm deep with the
|
|
|
|
|
13mm bit provided) went from 14 to 19 over five charge-discharge cycles. We
|
|
|
|
|
also compared the drill with a standard mains powered Black and Decker drill
|
|
|
|
|
with hammer action and it proved to be able to drill holes about five times
|
|
|
|
|
as fast (taking between 20 and 45 seconds depending on how hard the user
|
|
|
|
|
pushed).
|
|
|
|
|
|
|
|
|
|
<p>One problem with using a power drill for SRT bolt holes is that the holes
|
|
|
|
|
drilled have conical ends and so it is very dodgy putting the standard
|
|
|
|
|
self-drilling anchors in as their strength depends on the wedge (cone) being
|
|
|
|
|
driven in by the end of the hole. If this end is not flat the wedge may move
|
|
|
|
|
further into the hole rather than properly expanding the spit. It is also
|
|
|
|
|
difficult to drill the holes to exactly the right depth with the drill, where
|
|
|
|
|
only about 1.5mm of error either way can be accepted. Both these problems can
|
|
|
|
|
be dealt with by finishing off each hole with the standard self-drilling
|
|
|
|
|
technique but this means that a complete normal bolting kit must be carried
|
|
|
|
|
along with the Drill bolting kit, which means yet more gear and is not a very
|
|
|
|
|
pleasing solution.
|
|
|
|
|
|
|
|
|
|
<p>A better solution is to use different anchors, specifically designed for
|
|
|
|
|
use in conical holes. Discussions with Messrs Cordingley and Carter one night
|
|
|
|
|
in Green Close about their aven bolting activities produced a recommended
|
|
|
|
|
anchor - the Hilti HDK. These are also quite happy in holes which are too
|
|
|
|
|
deep as they don't use the end of the hole at all.
|
|
|
|
|
|
|
|
|
|
<p>We found the Cambridge Hilti distributor and boogied on down with grubby
|
|
|
|
|
surveys clutched in our sweaty paws with intent to scrounge/buy some anchors.
|
|
|
|
|
The Hilti man was astounded to discover that we were using spits around their
|
|
|
|
|
maximum stated loads, carefully ignoring the usual safety margin! Having
|
|
|
|
|
decided that we were nutters he was very helpful, demonstrating the HDK spits
|
|
|
|
|
with their internal wedges which are driven out with a special driver, and
|
|
|
|
|
photocopying the spec (see later). We even got a 15% discount out of him. We
|
|
|
|
|
would have liked to buy stainless anchors in the interests of longevity, and
|
|
|
|
|
thus indirectly safety and conservation, but at 28 quid for a box (100) of
|
|
|
|
|
galvanised and 109 quid for a box of stainless we decided that we couldn't
|
|
|
|
|
afford to be altruistic.
|
|
|
|
|
|
|
|
|
|
<p>Tony provided a block of limestone which had been destined for someone's
|
|
|
|
|
rock garden to further our experiments as all the Hilti figures were for
|
|
|
|
|
concrete, as were our kerbstone holes. We had expected to get many fewer
|
|
|
|
|
holes per charge but only actually got about 10 to 15% fewer. We now changed
|
|
|
|
|
to using a 10mm bit to correspond with the new HDK spits. These spits have
|
|
|
|
|
the same 8mm thread as the old spits (so all our hangers would fit) but can
|
|
|
|
|
have thinner walls as they don't have to be strong enough to be hammered
|
|
|
|
|
whilst drilling.
|
|
|
|
|
|
|
|
|
|
<p>With this smaller bit we got significantly more holes per charge although
|
|
|
|
|
there was significant variation in how many we actually got (between 34 and
|
|
|
|
|
22). We assume that this variation was caused by different duty cycles,
|
|
|
|
|
temperature and technique. We tried drilling holes with heavy pressure as
|
|
|
|
|
fast as possible which resulted in both drill and battery becoming very hot,
|
|
|
|
|
and drilling with lighter pressure and a 5 second gap between holes which
|
|
|
|
|
gave a cooler drill and more holes.
|
|
|
|
|
|
|
|
|
|
<p>We also tried placing a couple of bolts and found that when setting them
|
|
|
|
|
the driver wouldn't quite go all the way in, as it had when demonstrated in
|
|
|
|
|
the shop (in air), and when used on KK. We wondered about this but didn't
|
|
|
|
|
realise that it was to become more significant in Austria.
|
|
|
|
|
|
|
|
|
|
<p>A limited rock surface, the time consuming nature of the tests, and the
|
|
|
|
|
complaints about noise and vibration from three floors up (the rock was
|
|
|
|
|
living on Del's Churchill windowsill) all conspired to limit the total amount
|
|
|
|
|
of testing, making our conclusions somewhat tentative.
|
|
|
|
|
|
|
|
|
|
<p>It seemed from our experiments that the supplied battery had sufficient
|
|
|
|
|
capacity to be useful so only one spare would be required for recharging back
|
|
|
|
|
down at base. Also some practise in drilling the holes and placing the spits
|
|
|
|
|
before trying it underground is beneficial.
|
|
|
|
|
|
|
|
|
|
<p>So out in Austria Geraldine and a couple of BDH's, each containing bit,
|
|
|
|
|
driver and some spits, were transported up to the cave, along with all the
|
|
|
|
|
rest of the rubbish. Her first job was re-rigging Checkout (the third pitch)
|
|
|
|
|
yet again, and putting in bolts for the Dreamtime traverse (wielded by Dave).
|
|
|
|
|
The next day she was taken down to attempt the Yapate climb, and used to
|
|
|
|
|
re-rig Bungalow Pitch on the way (Jeremy taking three attempts to get a bolt
|
|
|
|
|
set properly as he hadn't practised it before).
|
|
|
|
|
|
|
|
|
|
<p>Unfortunately the battery went flat after just half a hole at Yapate. This
|
|
|
|
|
meant that despite the 30-odd holes on the surface, we were only getting nine
|
|
|
|
|
holes underground - bloody typical. This sort of performance continued
|
|
|
|
|
throughout the Expo, although the total use was not that high for reasons
|
|
|
|
|
which will become clear shortly. Unfortunately there was never an opportunity
|
|
|
|
|
to just use a whole battery in one go so the discharge always took place with
|
|
|
|
|
at least one night's sitting around between start and finish. We came to the
|
|
|
|
|
conclusion that a combination of the low temperature reducing the battery's
|
|
|
|
|
dischargeable capacity, and a high self-discharge rate whilst not in use gave
|
|
|
|
|
us this reduction in effective capacity.
|
|
|
|
|
|
|
|
|
|
<p>After the flat battery episode Geraldine sat around for a bit until a
|
|
|
|
|
tourist trip near the entrance started down Checkout. Mark Scott was the
|
|
|
|
|
unfortunate who tried to abseil from one of the rebelays rigged with the new
|
|
|
|
|
spits when it fell out. This, not surprisingly, led to some distrust of our
|
|
|
|
|
amazing new technology so Geraldine lay disused for a time until Wookey and
|
|
|
|
|
Dave brought her back up to the surface.
|
|
|
|
|
|
|
|
|
|
<p>The fact that it seemed to be impossible to set the spits according to the
|
|
|
|
|
instructions, (ie. getting the driver shoulder flush to the head of the
|
|
|
|
|
spit) was primary suspect for the spit not holding properly. The problem with
|
|
|
|
|
this was that if Dave couldn't set them then no-one else stood much chance.
|
|
|
|
|
The testing took the form of putting bolts into boulders, tying them to
|
|
|
|
|
something and throwing them off a nearby cliff. The first bolt split its rock
|
|
|
|
|
so we tried a bigger one (estimated at 40 kilograms). A ring hanger was used
|
|
|
|
|
as it could be loaded outwards, and about 2 metres of 10mm Edelrid attached
|
|
|
|
|
that to a sling hooked over a suitable projection.
|
|
|
|
|
|
|
|
|
|
<p>A fall factor one test went off fine so we tried a couple of Fall Factor
|
|
|
|
|
2s and still failed to even damage anything. We then tried throwing the rock
|
|
|
|
|
downwards to get a fall factor higher than two but on the second attempt at
|
|
|
|
|
this the sling bounced off and the rock bounced down the mountain. It was
|
|
|
|
|
retrieved but snapped in half across the bolthole as it was being dragged
|
|
|
|
|
back uphill. The set spit could thus be examined and it could be seen that it
|
|
|
|
|
really didn't expand very much at all inside the rock.
|
|
|
|
|
|
|
|
|
|
<p>Next we searched for a really big rock which was sufficiently close to the
|
|
|
|
|
edge that we could slide it off. The one chosen was estimated to weigh 150
|
|
|
|
|
kilograms. This did the trick and snapped the tape with what was probably
|
|
|
|
|
slightly less than a fall factor one fall. The rock shattered in the fall so
|
|
|
|
|
we were able to retrieve the remaining 30 kilogram bit with the hanger in it
|
|
|
|
|
to put on display as testimony to the strength of Hilti spits. The rope
|
|
|
|
|
sheath had melted just above the Figure of Eight through the ring hanger, and
|
|
|
|
|
it was probably this which had caused the burning smell we had noticed as the
|
|
|
|
|
rock fell. We assume that the rope must have been slightly nicked or damaged
|
|
|
|
|
at this point as one would expect it to melt or snap at the knot in this sort
|
|
|
|
|
of test.
|
|
|
|
|
|
|
|
|
|
<p>This testing convinced us that the new spit and drill combination was fine
|
|
|
|
|
as long as the driver shoulder goes to within at least 2.5mm of the spit.
|
|
|
|
|
However, it shed little light on the reason for the bolt failure. We can only
|
|
|
|
|
assume that it was not set well enough, and users should make an effort to
|
|
|
|
|
belt them as hard as possible to ensure reasonable setting. This attitude can
|
|
|
|
|
be taken too far, as was demonstrated by Del and Dave on the very last day's
|
|
|
|
|
pushing when they sheared one of the drivers off whilst attempting to ensure
|
|
|
|
|
that the spit was properly set.
|
|
|
|
|
|
|
|
|
|
<p><center><a href="hilti1-300.png"><img alt="before setting - 1k png"
|
|
|
|
|
width=530 height=90 hspace=10 vspace=10 src="hilti1-100.png"></a><br>
|
|
|
|
|
<b>Hilti HDK spits before and after setting.</b><br>
|
|
|
|
|
<a href="hilti2-300.png"><img alt="after setting - 1k png"
|
|
|
|
|
width=220 height=94 hspace=10 vspace=10 src="hilti2-100.png"></a></center>
|
|
|
|
|
|
|
|
|
|
<p>Geraldine was next used down at the bottom of Endless to rig the Hasta La
|
|
|
|
|
Vesta/Captive Wedge/Half Shaft series over a couple of trips. This allowed a
|
|
|
|
|
couple of silly rebelays to be rigged which would have been practically
|
|
|
|
|
impossible to do by hand. It also demonstrated just how fast rigging can be
|
|
|
|
|
done with the aid of a drill.
|
|
|
|
|
|
|
|
|
|
<p>Overall the drill was used much less than it could have been due to lack
|
|
|
|
|
of confidence, lack of experience, and poor battery logistics. Despite the
|
|
|
|
|
fact that we had two batteries no-one could be bothered carrying Animal's big
|
|
|
|
|
one underground as it promised no more power than the standard battery.
|
|
|
|
|
Inefficiency also resulted from the battery's habit of discharging itself if
|
|
|
|
|
left waiting in the cave. Hopefully these problems can be resolved next year
|
|
|
|
|
to make better use of Geraldine. A new battery will be constructed and some
|
|
|
|
|
more thorough tests done to discover how we can get the best out of it. A new
|
|
|
|
|
baggy will also be made as the original is damaged, and needs a bit of
|
|
|
|
|
redesign anyway. Also, anyone who expects to use the drill next year should
|
|
|
|
|
have a practice above ground first. And finally, discussion with Hilti will
|
|
|
|
|
hopefully produce some solution to the problem of insufficient expansion in
|
|
|
|
|
limestone.
|
|
|
|
|
|
2004-04-29 16:24:54 +01:00
|
|
|
<hr />
|
2001-08-15 19:29:27 +01:00
|
|
|
<!-- LINKS -->
|
2004-04-29 16:24:54 +01:00
|
|
|
<ul>
|
|
|
|
|
<li><ul>
|
|
|
|
|
<li>Photo of the <a href="../../handbook/l/bosch.htm">drill in use</a></li>
|
|
|
|
|
</ul></li>
|
|
|
|
|
<li>Cambridge Underground 1991,
|
|
|
|
|
<a href="../../../jnl/1991/index.htm">Table of Contents</a></li>
|
|
|
|
|
<li>1990 Expedition info:
|
|
|
|
|
<ul>
|
|
|
|
|
<li><a href="index.htm">Index</a> (more detail than in this list)</li>
|
|
|
|
|
<li><a href="log.htm">Logbook</a></li>
|
|
|
|
|
<li><a href="report.htm">Expo Report</a> (Diary)</li>
|
|
|
|
|
<li><a href="cavegd.htm">161 Description</a> to date (ie. 1990)</li>
|
|
|
|
|
<li><a href="162163.htm">Entrances 162 and 163</a></li>
|
|
|
|
|
<li><a href="newent.htm">New Entrances</a></li>
|
|
|
|
|
<li>Surveying Report:
|
|
|
|
|
<ul>
|
|
|
|
|
<li><a href="svy1.htm"> 1: Calibration</a></li>
|
|
|
|
|
<li><a href="svy2.htm"> 2: Survey Production</a></li>
|
|
|
|
|
</ul></li>
|
|
|
|
|
<li><a href="sponsr.htm">Sponsors</a></li>
|
|
|
|
|
</ul></li>
|
|
|
|
|
<li><a href="../../pubs.htm#pubs1990">Index</a> to all publications</li>
|
|
|
|
|
<li><a href="../../index.htm">Back to Expeditions intro page</a></li>
|
2004-04-30 22:56:57 +01:00
|
|
|
<li><a href="../../../index.htm">CUCC Home Page</a></li>
|
2004-04-29 16:24:54 +01:00
|
|
|
</ul>
|
2001-08-15 19:29:27 +01:00
|
|
|
</body>
|
|
|
|
|
</html>
|
