UKC

/ Concrete screws for sport climbing

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Ruth A - on 07 Apr 2017
Just curious if these are ever used to bolt crags, and if not why not? I am not sure if I have ever come across them sport climbing, but I have never looked that hard.

2
stp - on 07 Apr 2017
In reply to Ruth A:

Not entirely sure what you mean but the main bolt types for climbing are usually glue ins or some kind of expansion bolt.

If you mean screws that screw directly into the rock then I think a fear would be that constant shock loading might weaken the threads cut in the rock after a time. Then they'd get rattly and become unsafe.

I can't think any advantages either ?
JLS on 07 Apr 2017
In reply to Ruth A:

As said above, plus their load capacity isn't up to the mark deamed safe for climbing.

Rick Graham on 07 Apr 2017
In reply to stp:

I work in construction and with fellow workmates often muse " how did we manage before " thunderbolts " or concrete screws. Easy and quick to fix, and removeable.

I use them for temporary fixings when bolting routes.

For permanent climbing bolts they may have the disadvantage that stp suggests of coming loose.

Also not readily available in stainless, it may be that SS is not hard enough for the cutting threads.

Personally, I think they could be ideal for short term bolt positioning on new routes.
The stress of cutting the threads will test the rock quality. The position can be changed if the first choice is not ideal, sometimes routes need to settle down if the initial rock cleaning is not 100%.
A quality SS or titanium glue in can then be used as a permanent anchor in the re drilled out hole.

The big negative to the last paragraph,of course, is that they are not climbing/PPE/CE rated.

So far I have placed them on slate and limestone.
My bolt extractor device easily pulls out 12mm though bolts.

Attempts to pull test the thunderbolts ( on slate ) have ended with a stupidly stretched Petzl hanger.
The thunderbolt stayed put, quite encouraging.

So, quite a good question, Ruth. Worth some further investigation, I agree.
atthedropofahat on 07 Apr 2017
In reply to Ruth A:

Glue ins like resin anchors fracture the rock the least, preserving it's integrity. Concrete screws work but an fracture rock as they are driven in, many rocks are more brittle than concrete.
kristian - on 07 Apr 2017
In reply to Ruth A:

https://www.thebmc.co.uk/bolt-failures-on-north-wales-limestone

I too have used them but only as a cleaning bolt. They get removed or drilled out to a larger diameter for a resin bolt.
jimtitt - on 07 Apr 2017
In reply to Ruth A:

They have been tested, both by the DAV and the Australians. They are too weak in soft rock which is all they will go into as hard rock rips the threads off. The other problem is in medium to hard rock you physically can´ t screw them in unless you drill the hole oversize.
AP Melbourne - on 08 Apr 2017
In reply to jimtitt:

Down here in Upsidedownland a friend of mine was about 40m up a route on Taipan wall when he got shut down. He clipped directly in to a 'screw bolt', Untied His Rope, threaded it through the fixed maillon then re-tied. As he did so the bolt snapped and he took a flyer!
The torque involved with screwing in self-cutting bolts weakens them drastically. The route was re-equipped.
Scary stuff!!
AP.
Tradical on 08 Apr 2017
In reply to Ruth A:

They're sometimes used in bolt climbing underground...

This allows you to remove them and drill the hole out and replace with larger diameter resin anchors afterwards.

A little neater than leaving a load of expansion bolts up the wall to rot.
dunnyg - on 08 Apr 2017
Cheers all. Accidentally posted this on my friends account. I am using them as short term abseil anchors. Sounds like they are ok for that but not sure i would want to fall on them in a sport climbing situation. They are a lot less faff than resin/glue ins. I will probablu get some expansion bolts if i set up more permanent anchors. Their easy removal is also a plus point for my line of work.

I have been using them in limestone, just for information and they hold the weight of a couple of people with no obvious external problems. I havent removed any yet but doubt ill see anything too interesting if/when i do?
5
Tradical on 09 Apr 2017
In reply to dunnyg:

Caves are limestone, so presumably this rock type is more amenable to the technology.
1
dunnyg - on 09 Apr 2017
In reply to AP Melbourne:

I was warned about over torqing them. It seems pretty obvous when they are tight and if you have a small enough spanner it is reasonably difficult to over torque them I think. That does sound terrifying!
2
Andy Say - on 09 Apr 2017
In reply to dunnyg:

Not at Aldery Cliff by any chance?
1
Rick Graham on 09 Apr 2017
In reply to dunnyg:

> I was warned about over torquing them. It seems pretty obvious when they are tight and if you have a small enough spanner it is reasonably difficult to over torque them I think.

Easy answer. If the first thunderbolt is really struggling to cut a thread and possibly damaged by over torquing.
Remove it and a second thunderbolt will easily screw into the pre cut threads.

As Jim Titt has intimated, the exact hole diameter and rock hardness is crucial.
My own experience is that they appear to work quite efficiently on slate and limestone.

I have searched for a recommended max torque for installation, but even direct enquiries to technical departments have ended with a blank.
dunnyg - on 10 Apr 2017
In reply to Rick Graham:

Fair does. Sounds like they are just good for temporary bolting.

Not alderly cliff, out in Abruzzo in Italy!
jimtitt - on 10 Apr 2017
In reply to Rick Graham:

Heco (Multi Monti) give max recommended installation torque as 40N/m for 10mm and 55 for the 12 mm ones. The performance data in their tech info doesn´ t inspire me to ever want to clip one!
andrewmc - on 11 Apr 2017
In reply to Tradical:

> They're sometimes used in bolt climbing underground...

Yes, but so are 30mm long spit anchors :P
plus cavers don't fall on their bolts (at least not deliberately)...

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