andrewmc said:
Simon Wilson said:
A mixture of temporary, removable anchors such as concrete screws or Petzl Pulse and more permanent removable anchors such as resin anchors are perfect for caving.
Resin anchors (that are commercially available) are generally not removable (although I don't think this is a problem). That doesn't answer my question though.
I have gone to a lot of trouble researching concrete screws because I found it difficult to find authoritative information about them. I wrote an article and I have provided a link to it.
I have read it and I do find them interesting, which is why I asked the questions. Resin anchors are (probably) gloriously impractical for expeditions. This is where stainless concrete screws might have a niche but you didn't test them. If you were on expedition and were placing bolts that might be in long term use (and you can't practically place resins), what would you use?
How many resin anchors/concrete screws can you place in a day?
And can you drive concrete screws in with a drill?
Most resin anchors can easily be pulled out with a puller especially the IC anchor which was designed with removal in mind. Anchors fixed with epoxy resin can be removed by heating. Other resins including polyester and vinylester resins don't soften enough.
I think people shouldn't use anything they can't remove. Throughbolts are curse worse than Spits and drop-ins because they are extremely difficult to remove to the point where they will never be removed. I have managed to remove a few with very great difficulty. I have tried a lot and never found one that was drilled deep enough to push it in.
Resin anchors are very practical for expeditions. On expeditions people spend time dropping shafts once only and that is when concrete screws are perfect. It's easy to carry a drill around on the surface.
If a cave goes, often there comes a time as it gets deeper that you have to spend time rerigging the entrance pitches. You might decide to put resin anchors in if you think it's worth it. If you aren't caving round the clock but going back to camp at night then it's quite straight forward and you have plenty of time for the resin to set between trips.
The resin we have been using sets in about 20mins although a usually give it at least an hour before loading.
On an expedition, if a cave gets deep and you're going to have to come back the next year that's when resin anchors might come in. You would have to weigh up the options carefully and make a decision. It will take up time which you might not have but if you do have time, in most cases it would be straight forward to install resin anchors all the way out as you derig.
I know people like stainless throughbolts. If they understand all the factors and conservation issues, that's their choice if they are on a expedition and have the permission of the local cavers and/or authorities. They don't have any permission in the Dales and I destroy them when they get in the way of the anchor scheme, which we do have permission and support for.
I have not been able to get stainless concrete screws and I really can't see any point in them for caving use. Concrete screws are for temporary use so a life of a few years is plenty.
They have a tendency to come loose which is why I use the larger ones and tighten them tight.
If I remember correctly, think Sam Alshorn has installed about 14 resin anchors in one trip. How many concrete screws? As many as you could without running out of drill batteries - 50? 60? - a wild guess depending on the size. There are thousands installed on construction sites every day. Construction workers love them. They are so simple and reliable.
I would never try to screw them in with a drill although on construction sites they might use proper impact drivers with torque settings or sockets and ratchet or torque wrench. In caves I have used a ring spanner but prefer a socket and ratchet driver.
