mirror of
https://expo.survex.com/repositories/expoweb/.git/
synced 2024-11-22 15:21:55 +00:00
85 lines
4.3 KiB
HTML
Executable File
85 lines
4.3 KiB
HTML
Executable File
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0//EN">
|
|
<html>
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
|
|
<title>Cambridge Underground 1981: Slipping Ascenders</title>
|
|
<link rel="ToC" href="../../../jnl/1981/index.htm" title="CU 1981 Contents page">
|
|
<link rel="stylesheet" type="text/css" href="../../css/main2.css" />
|
|
</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 Eislufthöhle 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
|
|
Stellerweghöhle 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 -->
|
|
<ul id="links">
|
|
<li><a href="../../../jnl/1981/index.htm">Table of Contents</a>
|
|
for Cambridge Underground 1981</li>
|
|
<li><b>1980 Expedition info</b>:
|
|
<ul>
|
|
<li><a href="log.htm">Logbook</a><br>
|
|
<!-- <li><a href="bcracc.htm">BCRA Caves & Caving Report</a><br> -->
|
|
<li>Stellerweghöhle - <a href="descnt.htm">from Descent 49</a></li>
|
|
<li>Austria 1980 - from <a href="npcpub.htm">NPC Newsletter</a></li>
|
|
<li><a href="song.htm">Another Kick in the Balls</a> (expedition song)</li>
|
|
</ul></li>
|
|
<li><a href="../../pubs.htm#pubs1980">Index</a> to all publications</li>
|
|
<li><a href="../../index.htm">Back to Expeditions intro page</a></li>
|
|
<li><a href="../../../jnl/index.htm">Index</a> to Cambridge Underground</li>
|
|
<li><A HREF="../../index.htm">Back to CUCC top page</a><br>
|
|
</ul>
|
|
</body>
|
|
</html>
|