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scary self detaching bolt plates


rodw

27-Apr-2006
10:53:03 PM

Same as poeple who are now currently replacing carrots I imagine...nothing lasts forever but board I think inadvertently backed up the ring case because apparently...

"were surprising easy to remove, a simple twist with a bar to break the bond and pulled out with fingers"

So future problems of replacing them wont be a problem....

BoaredOfTheRings

27-Apr-2006
11:21:55 PM

On 27/04/2006 rodw wrote:
>So future problems of replacing them wont be a problem....

The mess left behind from the removal of the retro bolt in snow blind is an example of what can happen. Maybe monty go the glue right on that one.

But next time your clipping one of those glue ins on an overhanging wall and it's the only thing between you and the ground, have a think about whether it's one of those easy ones to remove!


nmonteith

27-Apr-2006
11:49:45 PM

On 27/04/2006 BoaredOfTheRings wrote:
>Hilti actually run a course in the placement of bolts, I wonder how many
>people placing glue ins out there have attended it.

A few years ago at leat 10 Chockstone users including myself attended an official Hilti bolting workshop.
We drilled, placed and tested ringbolts and threaded rod. From memory the rings held 4000kg before
failure!

mikl law

28-Apr-2006
7:18:41 AM

>>a simple twist with a bar to break the bond >>
Do the maths!
Hypothetical situation here:-
Using a 10mm rod, 100mm long, and 15 kg on a 60cm bar, the shear force on the bar at the OD is 17640N on a lever arm of 5 mm. The glue bond will take the same in shear or outwards tension, this is a straight outwards force of 1800 kg.

This would be poorly placed bolt to come out with such low forces (most carrots take a bit less to snap them off inside the rock however). Most times you'd have to use a 1m bar and a bit of grunt.

mikl law

28-Apr-2006
7:42:05 AM

I'm overcomplicating the issue:_
stress magnification (leverage) = 600 mm/5 mm = 120
Effective force on that radius rod = 120 X F = 120 X 15 = 1800 kg force
The same shear on the glue bond is required to break it by twisting or by outwards force. Therefore the bolt would have held an outwards pull of 1800 kg, and probabaly twice that straight down
The sensitivity of rings to twisting is evident from how easily they loosen with falls off to the side. Hence the move to U's. Glue in bolts with a fixed hanger also avoid twisting (as the bracket turns)


tnd

28-Apr-2006
9:24:15 AM

On 27/04/2006 kieranl wrote:

>Apart from drilling around it
>to excavate and then patching the hole I don't know what.
>
So what's so bad about that? It's easy to patch the hole with epoxy such that it's hardly noticable. And in fact a new ring, or the old one cleaned up, can be replaced in the excavated hole.


nmonteith

28-Apr-2006
9:45:22 AM

I have removed ringbolts with a funkness device attached to a big hammer. It takes about 20 minutes of
elbow shattering work to remove it - but the things do eventually come out without cratering the rock.


nmonteith

28-Apr-2006
9:47:09 AM

On 28/04/2006 tnd wrote:
>So what's so bad about that? It's easy to patch the hole with epoxy such
>that it's hardly noticable.

In the polished prefection of Arapiles or the Gramps any rock damage can be very noticible. Patching
with epoxy - no matter how hard you try - will never look pretty. In places like the BBlue Mtns were the
rock is more textured and chossy these rock scars are much harder to spot.

climberman

28-Apr-2006
10:29:14 AM

On 28/04/2006 nmonteith wrote:
> In places
>like the BBlue Mtns were the
>rock is more textured and chossy these rock scars are much harder to spot.

Oi ! You leave our textured choss alone !


anthonyk

28-Apr-2006
11:06:01 AM

On 28/04/2006 tnd wrote:
>So what's so bad about that? It's easy to patch the hole with epoxy such
>that it's hardly noticable. And in fact a new ring, or the old one cleaned
>up, can be replaced in the excavated hole.

what sort of size hole are we talking about?


tnd

28-Apr-2006
11:17:26 AM

On 28/04/2006 anthonyk wrote:
>On 28/04/2006 tnd wrote:
>>So what's so bad about that? It's easy to patch the hole with epoxy such
>>that it's hardly noticable. And in fact a new ring, or the old one cleaned
>>up, can be replaced in the excavated hole.
>
>what sort of size hole are we talking about?

About twice the size of the hole made for the ring, say 30mm across. As Neil says above, Blue Mtns rock is possibly more camouflaged.

Treviso

4-Jul-2006
3:21:17 PM

I actually had the problem at a crag in Sydney(Bangor West). I found that if the bolt wasn't quite in far enough or the rock tapered off on one side of the bolt you could actually get the bracket off with the QD in. It took a bit of effort, but as with Murphy's Law it finds a way off when you don't need it to.

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