Digest #4745 Wed Feb 2 22:31:36 1994 The Cavers Mailing List Digest Date: Thu, 03 Feb 94 13:58:16 GMT From: Wookey Subject: Re-bolting Simeon brings up the subject of re-bolting with eco-hangers (P-hangers to most of us), in relation to the 'other peoples rigging' thread. I agree with him that smearing epoxy on his ropes, just to clean tools/hands is indefensible. In mitigation I would say that unless you have tried installing P hangers it is difficult to imagine just how hard it is to keep the gunge under control - the gooking of his rope may well have been accidental. I have done a bit of re-bolting in Yorkshire. I was the mug that volunteered to do Tatty Wife (as Cambridge UCC's Adopted Cave - quite why we adopted one so far from the road I don't know!). If you have any comments now you know where to address them. For those who don't know, a bit of background: The UK has a lot of significantly vertical caves in Yorkshire and Derbyshire, generally between 100 & 200m deep. These were originally explored using ladder and lifeline techniques, with either natural or big rawlbolt/stemple belays. 10-12 years ago SRT started to become popular and many of the most popular caves were rigged for Alpine-style SRT with lots of M8 self-drilling spits (mostly reffered to as 'bolts'). Much of this work in Yorkshire was undertaken by one man (Dave Elliot) and caused massive controversy, especially as he then went on to make money from all this 'vandalism' by publishing an SRT rigging guide. Despite the non-cunsultative nature of this work, it is fair to say that his routes became extremely popular, and at least his bolting and rigging was sound (some would say excessive). There are an awful lot of crap bolts that have been put in since by others. The result of this popularity is that the M8 spits eventually wore out. This became obvious a few years ago when a couple of accidents occured - although none were fatal so far as I know. New bolts started springing up all over the place, contributing to 'Bolt farms' at pitch heads. The overall standard of re-bolting was not particularly high. It was clear that something more organised should be done - and that this time round proper consultation should take place, and a solution be found which was more long lasting, replaceable, safe etc. Discussions resulted in glued-in (Hilti C40 epoxy resin) eco-hangers (stainless P shaped hangers in 18mm dia by 80mm deep holes) being chosen. The main advantage of this system is that the holes are not stressed, unlike most other fixing systems, so they should be re-usable when the hangers eventually wear out. Also the hangers can also be tested in situ, they are (should be? - see later) very strong - up to 4 tons. Disadvantages are that it is very expensive (10 quid for a tube of resin which does about 5 holes, and 2 pounds 50 for each hanger), they need big holes, which means power drills, and to some extent the technology is not well tested. The time pressure to pick a reasonable solution and get on with it was quite high, as bolts were wearing out all over the place, and various independent re-bolting projects were happening anyway. Hilti had designed the resin for fixing things into concrete, rather than limestone, but then industrial fixings people are always rather astonished when they see what cavers think of as a bombproof belay! The effectiveness of the resin in limestone, or its long-term performance were unknown. This resin was chosen as limestone is chemically relatively similar to concrete (as opposed to brick - their other adhesive option). Tests using a hydraulic puller in rowten pot after only a 4 hour (rather than the specified 24 hour) curing period gave very good results (over 3 tons for a straight pull, I think). Further tests were done later to see what the effect of 'real conditions' would be. Holes were drilled in various bits of rock and left a) full of water, b) still with the drilling dust in, c) over drilled to 20mm and d) installed with a home-made equivalent hanger. All of these managed a direct pull of at least 1 tonne which whilst not being stunning was still adequate. These results were somewhat confused by the bits being fished out of a local quarry, and they all split during the pulls, almost certainly reducing the readings (but it did allow us to examine the surfaces to ascertain failure modes). Bolting training sessions were orgaised in the very easey-access Yordas cave (which now has a rather odd selection of hangers all the way along one wall at an easy drilling height). These are intended to be used for long term tests. These emphasised the importance of properly cleaning the holes, and attempting to roughen the inside of the hole to provide better keying. The glue capsules are designed to be used by workmen and thus are pretty idiot-proof. They have a screw-on mixing nozzle which thoroughly mixes the two-part resin by the time it is delivered to the tip. The downside of this system is that once you have started you have only a few minutes (depending on the ambient temperature), to get to the next hole, and so on. This means that when actually installing hangers you have to drill all the holes, then go back to the top, saw open a tube, and start squirting and abseiling like a fury. To get back to the original point, it is here that the difficulty of the whole exercise makes itself apparent. You are usually hanging out over a void somewhere, often trying to use a very long glue gun in a narrow space, holding in the hanger with one hand, squirting with the other, and holding open a plastic bag to catch the drips of gook with a third. You can't use any of the newly installed hangers to rig from, and you mustn't disturb any of them, and if you have put any in the roof you need a volunteer to hold them in place until they start to set. You also have only a few mins to get to the next pitch with all your kit before the glue sets in the nozzle, and without squirting it all over the cave en route. All this is made much harder by the fact that the mixing nozzle and the viscosity of the resin combine to ensure that you need a lot of pressure on the gun to get glue out of the end, and when you stop squeezing it countinues to dribble for some time, unless you remeber to release the ratchet (which tends to get jammed up with glue or mud - good design that!) All in all, it's a good game. More important than all this technical fascination is the placement of these hangers, which are destined to be a fixture for many years to come. There is plenty I have to say about that too, but not just now - I really ought to do some work! And then I could go on about how many bits and bobs you need to get up the hill and down the cave in working order otherwise you just have to forget it and go home - again! wookey