Quote from: tim.rose2 on February 18, 2019, 06:18:12 pmUnfortunately they were install incorrectly with the bolt head being proud of the surface rather than the welded part set down into a groove.I guess since neither U-staples (are people really still making and using them?) nor the BP anchors now generally being installed (at least by the bolt fund) need to be recessed (the twisted leg makes this unnecessary, according to the manufacturer) Portland climbers would never normally need to recess an anchor head.
Unfortunately they were install incorrectly with the bolt head being proud of the surface rather than the welded part set down into a groove.
I don't think any manufacturers of resin anchors recommend countersinking them. It was a measure introduced by cavers to reduce the movement of loose anchors. I can't see why a twisted leg would make any difference to the movement of a loose anchor.
Quote from: Simon Wilson on February 19, 2019, 08:21:27 amI don't think any manufacturers of resin anchors recommend countersinking them. It was a measure introduced by cavers to reduce the movement of loose anchors. I can't see why a twisted leg would make any difference to the movement of a loose anchor.I assumed that the countersinking was to increase the resistance against rotation to prevent anchors becoming loose (i.e. breaking the relatively weak adhesive glue-anchor bond) in the first place, rather than reducing the wobble of anchors that have already, to some degree, 'failed'.Something like the Fixe or Petzl resin anchors have little or no mechanical keying against rotation. Presumably the point of countersinking is that the sticky-out-ness of the head provides something to resist rotation. The BP anchors (and probably yours as well as they don't have a round cross-section, although possibly less so) have significantly more sticky-out-ness to resist rotation than an otherwise round anchor.Note my use of the technical term sticky-out-ness.
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.
Quote from: Simon Wilson on February 19, 2019, 08:49:27 amI 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.
Quote from: andrewmc on February 19, 2019, 11:44:04 amQuote from: Simon Wilson on February 19, 2019, 08:49:27 amI 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?
Are you talking ionic or covalent bonds, Simon?
You have shown evidence that there is a bond. You have not shown any evidence that there is a chemical bond. If you maintain that there is a chemical bond can you explain how it occurs? What is the chemical interaction between the stainless steel and the resin?
Quote from: Simon Wilson on February 19, 2019, 04:06:00 pmYou have shown evidence that there is a bond. You have not shown any evidence that there is a chemical bond. If you maintain that there is a chemical bond can you explain how it occurs? What is the chemical interaction between the stainless steel and the resin?Ah, apologies for misleading you; I was thinking of a form of chemical bonding known as Van der Walls bonding rather than covalent or ionic bonding. My use of the adjectives chemical and mechanical was an attempt to clearly differentiate between two types of bonding present in this system rather than to imply that there had been a major chemical reaction between resin and metal surface as you appear to have understood.Can you suggest better descriptors for these two mechanisms which help an resin bonded anchor to resist the extraction force?
More significantly, this debate started from a question about the effort required to extract an anchor. Do you accept that even when the form of bonding which stops movement of the anchor has failed, ...
... that the Eco & BP anchors still requires a substantial force to extract?
I emphasise that I am not suggesting that a slightly moving anchor does not need to be replaced at some time. But that the evidence for Eco and BP anchors does mean that a slightly moving anchor does not need to be immediately taken out of use.
Quote from: Bob Mehew on February 19, 2019, 06:49:52 pm I emphasise that I am not suggesting that a slightly moving anchor does not need to be replaced at some time. But that the evidence for Eco and BP anchors does mean that a slightly moving anchor does not need to be immediately taken out of use.But you're only guessing. Personally, if I'm going to hang my life off a 25 year old anchor I'd like more than one person's insufficiently informed guess about it's reliabilty.