What's Wrong With This Anchor?

[moabfool]

This anchor is shown on zionpermits.nps.gov on their permit reservation page. I took this picture last Friday (Nov 29th) in Mystery Canyon. I can see at least three thing that are potentially wrong with the anchor as it is installed, aside from the fact that it's bolted (thanks Shane).

[Brian in SLC]

I can see at least three thing that are potentially wrong with the anchor as it is installed, aside from the fact that it's bolted.

Hmmm. There's a lot to like about it. For one, its bolted (ha ha).

Very few things to be critical of from my POV.

Looks like a set of stainless glue ins. Plus on both. Really, glue ins have got to be the best solution for the softer sandstone. Nicely done.

Position looks like it minimizes rope grooves as its pitched out over a small scoop in the rock. Plus again.

Could probably eliminate the rapides that are connected to the bolts but, its almost nice that folks are adding these as they'll keep folks from thinking about rappelling directly off the bolts (which would groove them out and ruin their placements). But, not really a negative.

Webbing is a nice, natural color. Plus.

Anchor ends in a compact single rapide, which, some folks don't like due to a lack of redundancy but is fully bomber and, small enough for the silly biner or knot blocks folks seem to have to use. Not really a plus, though, as a ring would distribute wear better, but, still, its totally replaceable when worn so that's a plus.

Someone who tied the webbing made a good attempt at a power point in the apparent direction of load. Nicely done.

Edge distance. The left-hand anchor almost looks a touch close to the edge of the scoop but, hard to see exactly. Better might have been a touch back, but, its close enough to effect reducing the rope grooves on rappel.

Distance between the anchors. Almost looks like they're a bit close, but, compact and reasonable. Probably should aim for an anchor length or two apart which they may come close to. Seems ok.

I guess, someone could have painted the stainless anchors, but, that can also be bad for glue adhesion and might be best done by hand with a brush at a later date. Still doable.

I'd probably rappel fully on either one of the bolts by themselves. Bomber rig. Nicely done. Looks new (newer to me at least). Anyone claiming responsibility? I've, uhh, seen folks with those types of glue ins before...

Kudos. Nice anchor.

Edit to add something else I like: there's a vertical distance between the placements too, which uses a different layer of rock (easy to see with the layers of rock in the photo). Bonus. I'd have probably gone more with a vertical set than the horizontal, but, personal preference.

Edit again: nicely placed the anchors flush to slightly below the rock surface. That's not an accident but someone who knows what they're doing. Not easily done. Very nice.

-Brian in SLC

[trackrunner]

canyon booty

I'm with Brian on this. He covered everything I see about it. I'll add that it looks like it's sharing the load well too. Maybe if it's in real life I could see something different.

[moabfool]

Here's what I see wrong with this anchor.

1) The lower left bolt is too close to the edge of the roll over. The center line of that bad boy should be at least four bolt lengths away from the edge. If bolts should be four bolt lengths away from each other they should be four bolt lengths away from the edge.


2) The quicklink (let's call them what they are) is half way over the edge. This is a specific no no when using a biner in a climbing anchor. It should translate to anchors that are less likely to see dynamic loading as well. This is actually a two-part problem because A) if the link were torqued across the relatively sharp edge it could cause failure of the link, or B) it could pull the bolt from the rock since the load would be in tension rather than in shear. The only saving grace is that the extension of the anchor prevents any torquing of the link. But that fact leads us to the fact that...

3) Neither bolt is truly in shear. Both bolts are somewhat in tension, the upper more so than the lower. This can cause the bolt to pull out of its hole. What's truly sad is that these bolts are less than two years old, and that they replaced well-placed bolts. Admittedly, problem #3 is difficult to diagnose from the photo.

[Brian in SLC]

1) The lower left bolt is too close to the edge of the roll over. The center line of that bad boy should be at least four bolt lengths away from the edge. If bolts should be four bolt lengths away from each other they should be four bolt lengths away from the edge.

Looks like a Petzl collinox. Per the tech notice, 125mm away from an edge, 120mm away from another anchor. Bolt installation depth is 70mm.

http://www.petzl.com/files/imagecache/product_outdoor_slideshow_image/files/node_media/coll.jpg



2) The quicklink (let's call them what they are) is half way over the edge. This is a specific no no when using a biner in a climbing anchor. It should translate to anchors that are less likely to see dynamic loading as well. This is actually a two-part problem because A) if the link were torqued across the relatively sharp edge it could cause failure of the link, or B) it could pull the bolt from the rock since the load would be in tension rather than in shear. The only saving grace is that the extension of the anchor prevents any torquing of the link. But that fact leads us to the fact that...

Quickie, rapide, rapide mallion, rapid link, all the same. Rope or harness would fail before that thing would.

Load appears to be directed straight away from the anchor and not down onto the edge. Yeah, not optimal though. But, one of the reasons to not load a biner over an edge is that the gate could open, really weakening the biner. This isn't the case with a ring or link that is screwed shut. Also, really depends on the load path, and, in this case the load really doesn't look like its in the direction that would load the link onto that edge, at least not fully (hard to tell from the photo).

My bet is the quick link is stronger than the rock (!). Rock would break before the link would. Can't imagine the bolt would lever out. Even under some type of fulcrum/lever type advantage, the force required to lever out the bolt is probably more than a rope and/or harness would hold. A person just couldn't generate that kind of force in any type of normal use of that anchor. Hard to imagine an abnormal use that would either.



3) Neither bolt is truly in shear. Both bolts are somewhat in tension, the upper more so than the lower. This can cause the bolt to pull out of its hole. What's truly sad is that these bolts are less than two years old, and that they replaced well-placed bolts. Admittedly, problem #3 is difficult to diagnose from the photo.

If you look at the Petzl tech notice, the bolts are nearly (or at least rated) the same strength in tension as in shear. But, they look WAY more loaded in shear than in tension.

http://www.petzl.com/files/all/technical-notice/Sport/P55%20COLLINOX%20P55500-E.pdf

I'm not sure how someone rappelling off that anchor would remotely load those bolts in tension...load looks nearly 90 degrees from the bolt shaft.

It's really easy to be critical of an anchor placement. And that's ok. But that anchor appears to have much more going for it than against it.

Fun stuff, though. Thanks!

-Brian in SLC

[nonot]

This is a great anchor, there's only one problem with it: I'm not in the canyon rappelling off it.

[ratagonia]

This is a great anchor, there's only one problem with it: I'm not in the canyon rappelling off it.

That the anchor is for a downclimb? a bit of an excess for a downclimb, but most rappel it as the last little bit is a bit high for my taste.

In general, looks like quite a good anchor. The guys who put these glue-ins in Mystery the year before last (identity known to the BC Desk, not known to me) did both a good and a bad job of them.

YES - they did a good job of putting in the bolts. They grooved out under them to put a place for the bolt-ring to sit into. No excess glue. But the first anchor (not shown) they put too far out, so that the old bolts are still required to be safe while clipping/setting up on the new bolts. They put them further out because they were worried about the rope pulling - but the rope pull is not a problem which a more careful analysis of the geometry. Replacing the old bolts with new glue-ins would have been better.

BAD - adding really, really cheap Chinese-made quicklinks to the bolt hangers is laughable. OK, they are big enough that even the super-cheap kind are probably OK, but... leads me to think that they are applying a rule without understanding the principle. Rapides on normal bolt hangers = good. Rapides on glue-ins = good, when the rope is fed directly through the rapides. Rapide on glue in, then webbing, then glue-in = excessive. the rapides do not have a functional purpose, and are cheap and scary. Get rid of them!

At the Mystery Falls rappel, they tried to improve the pull by putting the new glue-ins out another 2 feet, so the pulled rope would not drop down onto the rock and get stuck. Like I did, a few years ago. But... in that location, the rappel is hard to get rigged up and started, and the rope passes over a sharp edge (hard on the rope, makes the rope pull harder, and if used, will end up grooving out). Or, the anchor could be extended, but this will make this quite a bit lower and people already have a problem getting started on this rappel. The times I have done Mystery in the last few years, their new glue-ins were not rigged with webbing and not being used. The previous anchor has some good bolts and people seem to think is just fine.

(enough ranting, for the moment??)

Tom :moses:

[oldno7]

Ya really have to be looking for nit's to pick on this but I'll try.

The Petzl bolt(Bat'inox) is rated at 50kn in any direction of pull.=11,200ish. lbs. per bolt.

The "correct" epoxy has a rated strength of 40kn=9000ish. lbs.

The glue rating is for concrete, our sandstone falls far short of concrete for strength.

So there are 2 point's of contention in my mind--
1) As stated, you take a bolt with a 11,200lb breaking strength and add a quicklink rated around 1980swl. If we can say swl X 5 is roughly breaking strength, our quik link is around 10,000lbs. That's "if" it has a SWL mark on it. If not it is probably considerably less. I would prefer to use the Bat'inox by itself and trust my luck to it's 11,200lb strength.(X2 in this case)
2) If the weak link in this set up is the sandstone, then the OP may have a point, stating the one is a little close to an edge, as per page 1 in Petzl's instruction. http://www.petzl.com/files/all/technical-notice/Pro/P57_BATINOX%20P57100-E.pdf

I think it is good that canyoneers as a group are concerned about anchors and their strength, but I think at times we go overboard. This approach is probably better than going the other way. If we do the calculation's on this particular set up, we get--

1) 2 bolt's----22,400lbs
2) 2 quick links---20,000ish(maybe) definitely not needed
3) Redundant webbing---16,000lbs+
4) 5/16 quicklink---around 6000lbs
5) Rope---4-6000lbs
6) Rap device---3-7000lbs
7) Harness--4000ish

So if we go back to basic's and evaluate---

E--check
A--check
R--check
N
E--check
S--check
T--probably not

D--check
E--debatable
A--debateable
R--check(Tom may argue)

I like it, it could have been done better, but so could 90% of bolted anchors.

[Iceaxe]

aside from the fact that it's bolted (thanks Shane).

Just doing my job.... :haha:

That's actually one of the better bolted anchors out there.... we should be so lucky to see this good of job everywhere.

Below is a better representative of the fixed crap I see people rappelling on.

.

[trackrunner]

is a better representative of the fixed crap I see people rappelling on.

.

What no hardware store bolts or store eye bolts? I've seen those before. Very easy to pull out.

[Bo_Beck]

Not too sure how applicable this may or not be:

I used to be convinced that "glue-ins" were the answer to permanent anchors. Yesterday I went through a canyon that was approved under HCP, RCDR, and will eventually be open to the public. A lot of discussion went into anchors (or not anchors). Of the 6 possible rappels, 4 can be downclimbed. Anchors exist at 4 of the 6 possible/necessary rappels already. Some anchors are very questionable both for reliability and impact minimization. Discussion entailed of replacing anchors (part of the planning process) and what kind of anchors will be used. The discussion came up about "glue-ins". Currently there are 2 climbing areas close to town that "Petzl-type and or Petzl" glue ins have been used. On 2 separate climbs the glue-ins have become wobbly and spinny. There is no way to tighten these anchors.The rock type and quality in the canyon is similar to the climbing areas. Part of the thought is that there is very little surface area for glue retention on the shaft of these glue-ins. Something that has been used with greater success is 1/2 threaded rod (lots of surface area with the threads) which still has tremendous shear strength.

Thoughts? Experience?

(yeah, I know.....no bolts!)

[Brian in SLC]

The Petzl bolt(Bat'inox) is rated at 50kn in any direction of pull.=11,200ish. lbs. per bolt.

That's probably a collinox in the photo. But, close enough.


The glue rating is for concrete, our sandstone falls far short of concrete for strength.

Do you know what the rock is rated to? My bet is its very similar to the softer concrete. Here's some info from a site I'll post for Bo related to his glue in queston:

******************
Unconfined compressive strength:-
Granite 100-250 N/mm

[Brian in SLC]

Thoughts? Experience?

This site has some great info:

http://www.climbargolis.com/Glue-inBoltDesign.htm

Ton of variables when it comes to glue in bolts, which is why folks probably don't do them as much. Requires a ton of saavy. And equipment.

Sounds like someone honked up either the glue or the surface prep of either the hole or the bolt anchor if they are loose. Stainless glue in's are supposed to be very finicky for surface prep. My bet is if you handled them a ton without gloves on then you'd contaminate the surface to the point of the glue not sticking to them very well.

Cheers, Bo!

[Brian in SLC]

BAD - adding really, really cheap Chinese-made quicklinks to the bolt hangers is laughable.

I seem to recall "someone" busted a few of those cheap chinese made 1/4" ones and they did pretty well. Certainly not "laughable".

Recent thread on the 'taco discussing bolt anchors. Guy there has tested cheap quick links by fixturing them to a biner on the bumper of his truck and the other end of the rope to some large fixed object. His photo's are kinda funny. Anyhoo, the rope always breaks, never the link.

My bet is any link 5/16" or bigger has got to be strong enough, regardless of where it was made. You'd have to be missing half the material or more to be unsafe... Just the mass alone in grade 2 or whatever pig iron is strong enough.

Not that I prefer the small ones. Give me a 10mm stainless ring every time...

Anyhoo, we've gone down this "cheap v spendy" rapide thing before...

I, uhh, buy my 3/8" quick links at the dollar store for a buck per. My bet is you couldn't bust them on most Instrons...(although I've upgraded mostly to stainless 5/16" ones).

Cheers!

-Brian in SLC

[Scott Card]

. . . . . . and so in sum, to answer the question "what is wrong with this anchor", nothing really. :haha: (thanks for all the techy stuff)

[Iceaxe]

Yesterday I went through a canyon that was approved under HCP, RCDR, and will eventually be open to the public.

Now a stupied question.... what does HCP and RCDR stand for? :ne_nau:



Thoughts? Experience?

If I were a land manager I would probably stay as far away from dictating anchors as I could get..... I'm no lawyer but... It seems the minute a land agency starts specifying anchors they accept some responsibility and open themselves up to litigation.

:popcorn:

[Bo_Beck]

Now a stupied question.... what does HCP and RCDR stand for? :ne_nau:


Habitat Conservation Plan and Red Cliff Desert Reserve





If I were a land manager I would probably stay as far away from dictating anchors as I could get..... I'm no lawyer but... It seems the minute a land agency starts specifying anchors they accept some responsibility and open themselves up to litigation.

:popcorn:

The route was done many years ago, and yes bolted, prior to the land becoming part of the Red Cliff Desert Reserve and now subject to the regulations set forth by the Habitat Conservation Plan (non-cataloged trail, therefore illegal to hike). By careful and thoughtful requests, recreation user groups (explorers, canyoneers,climbers, hikers, etc) have sought out expansion of areas for recreation. Naturally the concerns of land managers address issues such as access, impact, safety, and the ability to measure these issues. Since the canyon we're dealing with had been done in the past, all of these issues are of concern. Rather than opening the canyon with the old hardwear in place, our thoughts as users is to replace any anchors that currently are outdated, unsafe and do nothing to mitigate impact (rope grooves) with safer, less impacting anchors. The Land Managers have nothing to do with, nor want to have anything to do with the decision of placing anchors.

[oldno7]

Holler if you want some help with any of these Bo. I'd be glad to come down.

[Iceaxe]

Thanks for the explanation....

If.... you are going to bolt.... than I vote for big, industrial strength, correctly installed and well placed glue-ins..... If you are going to do something you might as well do it right.

[trackrunner]

Holler if you want some help with any of these Bo. I'd be glad to come down.

X2

Agree with Shane let's do it right the first time if it's going to happen.

[oldno7]

Thanks for the explanation....

If.... than I vote for big, industrial strength,

Schedule 60--#5bar???
I have some in the yard :haha:

[Iceaxe]

If you want bolts to last you have to do a good enough job that I can't remove them..... :lol8:

:five:

[moabfool]

Looks like a Petzl collinox. Per the tech notice, 125mm away from an edge, 120mm away from another anchor. Bolt installation depth is 70mm.

-70mm depth: looks good (Do we really know? We assume the depth is correct because it's seated against the rock)
-120mm (about 4.5") away from other anchor: looks good
-125mm (about 4.75") away from the edge: does not look good.

My point is that the lower bolt should be back from the edge about another hand width. Yes, it's still better than many other bolts out there, but I will contend that it could have been back four of five more inches without causing any problems with rope pull.


If you look at the Petzl tech notice, the bolts are nearly (or at least rated) the same strength in tension as in shear. But, they look WAY more loaded in shear than in tension.

I'd feel very confident is saying that the 25 kN rating in tension and shear is only for the bolt its self. I'm very sure that Petzl makes no warranty as to the strength of the placement (see the rock strength chart). Almost any bolt placement is stronger in shear than in tension regardless of the relative tension/shear strengths of the actual bolt. IMO if something can be done to eliminate tension forces it should be done, even if it means a little grooving in some rock, especially one that no tourist will ever see. The only exception I can see is if the bolt is next to a sharp corner that will cut webbing or rope. That's not the case here, but I've seen it happen. The crappy part is that I was the one dangling from the rope when it started to cut. Since y'all will want to know; we were climbing at Red Rocks near Vegas, I was off fall-line when I fell, and the rope cut over half-way through.

[Brian in SLC]

My point is that the lower bolt should be back from the edge about another hand width. Yes, it's still better than many other bolts out there, but I will contend that it could have been back four of five more inches without causing any problems with rope pull.

It looks, from the photo, too close to that edge to me too. Not a full sharp edge, more of a scoop, but, yeah, could have been placed further back for sure.


I'd feel very confident is saying that the 25 kN rating in tension and shear is only for the bolt its self.

Ha! Probably correct. Good point.

Still, even though its hard to tell from the photo, if I imagine the bolt shaft position into the rock, run an imaginary line straight out, and estimate the angle of the slings in relation to the bolt shaft line, it looks near 90 degrees, and, not any where near zero degrees. Really does look very loaded in the shear plane.


The crappy part is that I was the one dangling from the rope when it started to cut. Since y'all will want to know; we were climbing at Red Rocks near Vegas, I was off fall-line when I fell, and the rope cut over half-way through.

What route?

Sounds scary as heck. Just the sheath or through the innards too?

Had kind of a similar thing earlier this year juggin' a rope. Thought it was fairly well positioned and straight down, but, went over the smallest of subtle edges. Took a foot of sheath off my lead climibing rope. Ahhh, was ready for retirement anyhow...thankfully got my use out of it.

The rock doesn't always present itself out there in the wild with easy and/or obvious solutions. Always good to have that critical eye.

Cheers!

-Brian in SLC

[ratagonia]

Looks like a Petzl collinox. Per the tech notice, 125mm away from an edge, 120mm away from another anchor. Bolt installation depth is 70mm.

-70mm depth: looks good (Do we really know? We assume the depth is correct because it's seated against the rock)
-120mm (about 4.5") away from other anchor: looks good
-125mm (about 4.75") away from the edge: does not look good.

My point is that the lower bolt should be back from the edge about another hand width. Yes, it's still better than many other bolts out there, but I will contend that it could have been back four of five more inches without causing any problems with rope pull.


If you look at the Petzl tech notice, the bolts are nearly (or at least rated) the same strength in tension as in shear. But, they look WAY more loaded in shear than in tension.

I'd feel very confident is saying that the 25 kN rating in tension and shear is only for the bolt its self. I'm very sure that Petzl makes no warranty as to the strength of the placement (see the rock strength chart). Almost any bolt placement is stronger in shear than in tension regardless of the relative tension/shear strengths of the actual bolt. IMO if something can be done to eliminate tension forces it should be done, even if it means a little grooving in some rock, especially one that no tourist will ever see. The only exception I can see is if the bolt is next to a sharp corner that will cut webbing or rope. That's not the case here, but I've seen it happen. The crappy part is that I was the one dangling from the rope when it started to cut. Since y'all will want to know; we were climbing at Red Rocks near Vegas, I was off fall-line when I fell, and the rope cut over half-way through.

I'm happy that you are 'very confident', but I don't know where you are getting your information. Can you cite a source? I think you are making things up, or misinterpreting some information you have heard. Don't make things up!!!

Mechanical bolts are designed as construction anchors and have an engineered, tested and claimed rating in both sheer and tension, in the material stated - usually several grades of concrete, for which Navajo Sandstone can be estimated to be the weakest grade of concrete. Properly set bolts, when new, are about the same strength in shear as in tension.

Properly installed glue in bolts are engineered to be just as strong in pure tension as they are in sheer. Otherwise, no one would make them - too much liability.

Assuming you are not simul rappelling two SUVs on that anchor, I don't think the expected loads will exceed the minimum strength, even if it is a tad under 1 L back from the edge. According the Mechanics of Solids (Mechanical Engineering Sophomore Course), once you are 1xLength back from the edge, moving further back makes no difference. You seem to think we are placing this in Green Jello - we're not, we call this rock a "solid", it follows the laws of physics that apply to a solid, at least at this scale.

Tom :moses: BS ME 1982

[nonot]

Properly installed glue in bolts are engineered to be just as strong in pure tension as they are in sheer. Otherwise, no one would make them - too much liability.

The tensile strength of a bolt (ripping off the head of the bolt, or an eyelet off a ring bolt) is meaningless in canyoneering, the bolt will pull out of any wall when loaded in tension before you rip the head off (unless, you can get a nut and washer in behind it.)

Only exception is if it is really, really rusted to the point it is completely unsafe for anything.

[moabfool]

Properly installed glue in bolts are engineered to be just as strong in pure tension as they are in sheer. Otherwise, no one would make them - too much liability.

The tensile strength of a bolt (ripping off the head of the bolt, or an eyelet off a ring bolt) is meaningless in canyoneering, the bolt will pull out of any wall when loaded in tension before you rip the head off (unless, you can get a nut and washer in behind it.)

Only exception is if it is really, really rusted to the point it is completely unsafe for anything.

I spoke with a co-worker who worked for a sign company about bolts placed in a solid substrate. The company he worked for built and installed scoreboards, the really big ones. He said that both expansion bolts and glue bolts are slightly stronger in tension than in shear depending on the preparation of the hole. He also said that expansion bolts and glue bolts are stronger than J-bolts in tension because J-bolts have a tendency to "spaghetti." But given the fact that most holes drilled by canyoneers are probably not cleaned properly I am still inclined to trust a bolt in shear over a bolt in tension.

[Iceaxe]

But given the fact that most holes drilled by canyoneers are probably not cleaned properly I am still inclined to trust a bolt in shear over a bolt in tension.

You are opening up a whole new can of worms.... now you are betting on which type of "improperly" placed bolt is stronger....

The limitation with all these load charts is they are for "properly" installed bolts.... I could write a laundry list of where canyoneers usually fail to meet that requirement. But I'm pretty sure properly installed does not begin with a hand drilled hole.

Anyhoo.... if the bolts (expansion or adhesive) are properly installed the rest doesn't matter as the sandstone is where the system will fail.

:blahblah:

[ratagonia]

Properly installed glue in bolts are engineered to be just as strong in pure tension as they are in sheer. Otherwise, no one would make them - too much liability.

The tensile strength of a bolt (ripping off the head of the bolt, or an eyelet off a ring bolt) is meaningless in canyoneering, the bolt will pull out of any wall when loaded in tension before you rip the head off (unless, you can get a nut and washer in behind it.)

Only exception is if it is really, really rusted to the point it is completely unsafe for anything.

I spoke with a co-worker who worked for a sign company about bolts placed in a solid substrate. The company he worked for built and installed scoreboards, the really big ones. He said that both expansion bolts and glue bolts are slightly stronger in tension than in shear depending on the preparation of the hole. He also said that expansion bolts and glue bolts are stronger than J-bolts in tension because J-bolts have a tendency to "spaghetti." But given the fact that most holes drilled by canyoneers are probably not cleaned properly I am still inclined to trust a bolt in shear over a bolt in tension.

Yes, I prefer to trust a bolt in shear more than a bolt in tension. Here's the pdf on Power Bolts - compare the sheer and tensile strengths, and use the lowest-grade concrete as the match to good Navajo Sandstone.

http://www.powers.com/pdfs/mechanical/06914.pdf

That's about a 1 Meg file...

As far as 'properly cleaning holes' again, I ask, based on what??? Placing mechanical bolts is difficult and requires good cleaning, and I have seen bolts that run the range from very poorly placed to very well placed. Even well-placed ones will fail (ie, will wiggle themselves loose) in really soft rock (there's a place like that in Birch Hollow). Since I place more bolts for canyoneering than perhaps everyone else combined (though I have been lagging behind, the last two years, and those guys in Mystery certainly placed a bunch), I can tell you that I clean my holes quite well.

Glue In Bolts require substantial equipment and hassle to place. And knowledge. I think anyone going to all that trouble will work hard to clean the holes well - although Brian's comment about how excess handling of the bolts can contaminate them with skin oils shows how technical and touchy the whole system is.

Tom :moses:

[ratagonia]

But I'm pretty sure properly installed does not begin with a hand drilled hole.

Anyhoo.... if the bolts (expansion or adhesive) are properly installed the rest doesn't matter as the sandstone is where the system will fail.

:blahblah:

Holes can be drilled well by hand, but of course, it takes skill to do so. I think any kind of drilling in very soft rock requires skill.

Tom

[Brian in SLC]

...I can tell you that I clean my holes quite well.

My bet is most folks do. If the bolt is snug, then, someone won at least part of that battle!

I clean the heck out of the holes I drill, more than any one else I've seen drill. But, I'm also using finicky stainless Powers bolts a lot and they are really sensitive to dirty holes (amongst a bunch of other things).

-Brian in SLC

[hank moon]

I'd feel very confident is saying that the 25 kN rating in tension and shear is only for the bolt its self.

25 kN is the rating Petzl gives to the ring (see technical notice). This figure is given probably just to satisfy the minimum requirements of the EN 959 standard on rock anchors for mountaineering. The actual strength of the ring (and the placed bolt) can be substantially higher in concrete (see test data chart, below).

Sandstone's a different story...