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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0//EN">
<html lang=en>
<head>
<title>Cambridge Underground 1981: Slipping Ascenders</title>
<link rel="ToC" href="../../../jnl/1981/index.htm" title="CU 1981 Contents page">
</head>
<body>
<center><font size=-1>Cambridge Underground 1981 p 22</font>
<h2>SLIPPING ASCENDERS</h2>
<p>Ben van Millingen</center>
<p>On expeditions to Austria in the last two years several types of ascenders
in different prusik systems were used. Pitches of varying lengths were
climbed in muddy, icy, wet, and dry conditions. The most popular prusiking
system used was the Frog, as its ease of handling was suitable on the pitches
encountered in Austria which tend to be long and split by rebelays. This
system in turn favoured the "Jumar" type ascenders rather than Ropewalkers.
<p>In Austria, caves under exploration were left rigged during the whole
expedition, being used by at least two people each day for two weeks. Some
ropes rigged in muddy areas of the cave became mud-coated straight away, but
after two weeks mud had spread onto nearly all the ropes, even in clean areas
of the cave. Mud was often transfered from dirty racks, but also just by
clothing rubbing against the ropes. The Fiesta Run in Eislufth&ouml;hle was
particularly bad - a sloping pitch with the rope being lost in the mud lying
on the wall. Similarly one arrived at the top of the big pitch in
Stellerwegh&ouml;hle as if one had just walked through a ploughed field.
Often the seemingly dry, dusty mud was the worst for producing a fine coating
of lubricant on the ropes. Under these conditions the difference between
ascenders showed most strongly.
<p>Jumars performed very well with almost no slippage, as did Petzls; by far
the worst were CMI's. Though they were little used, the most certain ascender
for use on muddy pitches were Ropewalkers, where the cam bites the rope by
direct application of the climber's weight. On muddy ropes CMI's frequently
slipped, providing an agonising ascent only made possible by fingering the
cams into position at each step. Usually only one ascender slipped at a time,
but occasionally the second slipped when shock loaded by the fall from the
first.
<p>Jumar type ascenders rely on spring loading to close the cam and thus grip
the rope. The spring may not have the force required to grip on a very muddy
rope, particularly if the cam teeth are also muddied. CMI's seemed especially
vulnerable to clogging with mud. Even if ascenders were cleaned at the bottom
of a pitch the cam was clogged with mud by the top.
<p>The spring in CMI's is much weaker than that of a Jumar, and so does not
provide sufficient force on a muddy rope to clamp it. Three springs distorted
so badly that the cam was able to flap loosely in the frame rendering them
useless. The cause of this might have been mud getting in behind the cam
where it is pressed by the thumb each time the cam is opened. Furthermore the
pin on which the cam pivots is held in place by a small circlip which does
not look up to the task. This should never be used again once removed, as it
is very easy to deform permanently.
<p>Though no serious accidents were experienced because of the failure of
CMI's; several people had falls which must have badly shock loaded both ropes
and bolts at the head of pitches. From these experiences I do not feel that
the design of CMI's is up to the conditions found underground.
<p><hr>
<!-- LINKS -->
<img alt="&gt;" src="../../../icons/lists/0.gif">
<a href="../../../jnl/1981/index.htm">Table of Contents</a>
for Cambridge Underground 1981<br>
<img alt="&gt;" src="../../../icons/lists/0.gif">
<b>1980 Expedition info</b>:<br>
<img alt="---&gt;" src="../../../icons/lists/1.gif">
<a href="log.htm">Logbook</a><br>
<!-- <img alt="---&gt;" src="../../../icons/lists/1.gif">
<a href="bcracc.htm">BCRA Caves &amp; Caving Report</a><br> -->
<img alt="---&gt;" src="../../../icons/lists/1.gif">
Stellerwegh&ouml;hle - <a href="descnt.htm">from Descent 49</a><br>
<img alt="---&gt;" src="../../../icons/lists/1.gif">
Austria 1980 - from <a href="npcpub.htm">NPC Newsletter</a><br>
<img alt="---&gt;" src="../../../icons/lists/1.gif">
<a href="song.htm">Another Kick in the Balls</a> (expedition song)<br>
<img alt="&gt;" src="../../../icons/lists/0.gif">
<a href="../../pubs.htm#1980">Index</a> to all publications<br>
<img alt="&gt;" src="../../../icons/lists/0.gif">
<a href="../../index.htm">Back to Expeditions intro page</a><br>
<img alt="&gt;" src="../../../icons/lists/0.gif">
<a href="../../../jnl/index.htm">Index</a> to Cambridge Underground<br>
<img alt="&gt;" src="../../../icons/lists/0.gif">
<A HREF="../../index.htm">Back to CUCC top page</a><br>
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