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The Dales / Re: High Birkwith caves - important
« Last post by Cave_Troll on Today at 02:48:42 pm »
remind me how much Alum Pot charges ?
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New To Caving / Re: First ever trip report
« Last post by Pitlamp on Today at 02:31:17 pm »
As the author of this masterpiece, I should perhaps point out that I am now a fully grown adult who writes in straight lines. I do, however, still draw rocks exactly like this on surveys.

 :lol:

By pure chance I have my own caving diaries in front of me (to look something up for someone). So I glanced at what I wrote about my own first proper trip in a real limestone cave. I was 14 and was with a school friend of a similar age - unsupervised by anyone else. The trip was to Dow Cave; the entry says: "Went as far as Hobson's Choice. Turned back because we couldn't find the way and had only one grotty light each. Met two hikers and they came with us."

Perhaps it's just as well that we didn't find the way . . .   :-\

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Peak District / Re: Anchors/P-Bolts - Treak Cliff Cavern
« Last post by bograt on Today at 02:29:37 pm »
MODERATORS--- Please straighten this thread out, I fail to see what Hydrajaws in a Yorkshire cave have to do with bolts in a Derbyshire cave---
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The Dales / Re: High Birkwith caves - important
« Last post by marysboy on Today at 02:06:12 pm »
I took the path from Selside to High Birkwith (on the bike)
marked on OS map as a public footpath (no bridleway rights for bike riding)
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Portland / Re: Blacknor Hole bolts
« Last post by Simon Wilson on Today at 01:17:20 pm »
I can't see why the shape of the cross section of the metal part of the anchor has any bearing on rotation of a loose anchor. With every anchor I've seen that has significant movement the whole resin plug is moving. The main reason why anchors become loose appears to be resin shrinkage.

Fair enough - although presumably less than fastidious cleaning of the hole with suitable brushes and blowers would also give a weak bond between resin and rock.
There was one embarrassed installer who used a washing up liquid bottle to jet water into the hole to clean them.  It was belatedly realised the loose anchors he had installed (no resin to rock chemical bond) was due to the bottle not having been thoroughly cleaned out. 

I should add that one of the checks on the resin has been to show it will work under wet conditions. 

In theory resin shrinkage occurs both ways, but presumably the 'irregularities' of the rock are far less than the designed 'irregularities' of most anchor types.  One of the positive features of the resin anchor is that even with the chemical bonding gone, the mechanical interference between resin and rock due to those irregularities still takes a lot of effort to overcome.  But no doubt the resin will wear with usage  once the chemcial bond has gone.

Have you published your shrinkage work Simon?

Chemical bonding? Can you give evidence for that?

A "lot of effort to overcome"? How much is a lot? How many times has this 'lot of effort' been seen?
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Portland / Re: Blacknor Hole bolts
« Last post by Bob Mehew on Today at 12:43:13 pm »
I can't see why the shape of the cross section of the metal part of the anchor has any bearing on rotation of a loose anchor. With every anchor I've seen that has significant movement the whole resin plug is moving. The main reason why anchors become loose appears to be resin shrinkage.

Fair enough - although presumably less than fastidious cleaning of the hole with suitable brushes and blowers would also give a weak bond between resin and rock.
There was one embarrassed installer who used a washing up liquid bottle to jet water into the hole to clean them.  It was belatedly realised the loose anchors he had installed (no resin to rock chemical bond) was due to the bottle not having been thoroughly cleaned out. 

I should add that one of the checks on the resin has been to show it will work under wet conditions. 

In theory resin shrinkage occurs both ways, but presumably the 'irregularities' of the rock are far less than the designed 'irregularities' of most anchor types.  One of the positive features of the resin anchor is that even with the chemical bonding gone, the mechanical interference between resin and rock due to those irregularities still takes a lot of effort to overcome.  But no doubt the resin will wear with usage  once the chemcial bond has gone.

Have you published your shrinkage work Simon? 
7
Peak District / Re: Anchors/P-Bolts - Treak Cliff Cavern
« Last post by thomasr on Today at 11:52:51 am »
 HYDRAJAWS  come up on fleabay  at the moment one nearly new showing.  Historic sale price £200-  £ 400
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Portland / Re: Blacknor Hole bolts
« Last post by andrewmc on Today at 11:44:04 am »
I can't see why the shape of the cross section of the metal part of the anchor has any bearing on rotation of a loose anchor. With every anchor I've seen that has significant movement the whole resin plug is moving. The main reason why anchors become loose appears to be resin shrinkage.

Fair enough - although presumably less than fastidious cleaning of the hole with suitable brushes and blowers would also give a weak bond between resin and rock.
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Equipment / Re: Bolt failures
« Last post by caving_fox on Today at 10:48:07 am »

A substantial part of the wall on the bottom pitch of Little Hull Pot which had a deviation P-hanger became detached and finished up at the bottom of the shaft. I wouldn't like to say that it was poor placement, however. Although the shaft is in a fault and the rock is inherently fractured, I would never have envisaged a whole chunk of the wall peeling off if I had been bolting it. The P-bolt was still standing firm and proud in the rock, only at the bottom of the pitch!


There's a small block at the bottom of an Oxlow pitch with a proud P bolt too. At the pitch head you're wishing for another bolt somewhere, and it's only when you get to the bottom that you find it. It's a cube of rock, a foot or so a side that failed.

Are you sure you're not thinking or Perl Chamber in Knotlow Cavern?

  :clap2: that'll be the one. Didn't know the chamber had a name.
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New To Caving / Re: First ever trip report
« Last post by mrodoc on Today at 10:34:33 am »
I found a diary entry the other day. I had just turned thirteen and was digging in the caves in Chard. The entry refers to a boulder needing to be shifted. We used those Price's candles then. Shame the rock wasn't limestone - the caves were slip rifts or from old quarrying.  It was another 3 years before we got to dig in a proper limestone cave on the Quantocks thanks to the Old Ruminator.
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