Author Topic: Why do hanger brackets get loose over time?  (Read 1454 times)

Offline sneoh

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Why do hanger brackets get loose over time?
« on: November 02, 2009, 09:05:08 pm »

Allow me to preface this inquiry by stating that I am not trolling, or trying to stir up controversy, or aiming to put  anyone or any organization down in any way.  My motives are straightforward but two-fold:
1. to know if there are technically sound reasons for why bolts or nuts that tighten the brackets to the rock get loose over time and with use (and falls),
2. to know if there are improvements which can be introduced into the hardware or bolting process that will lead to fewer loose brackets over time.  Yes, I do know the advantage that glue-in eyebolts have over purely mechanical fasteners and brackets in this area but, for better or worse, the right reasons or not, the latter will continue to be used for years to come.

On a related matter, I recently learned that there might be 'informal' trials at Red River Gorge of two possible improvements -
A.  use of Fixe hanger bracket that has three semi-perf dimples that dig into the rock face when the hanger is tightened down,
B.  application of a generous layer of weather resistant epoxy between the hanger and the rock.


I have been climbing for nearly 20 years and have clipped into probably more than my fair share of fixed protection.  I post this inquiry not out of overt fear or sheer ignorance but because of my belief that there are incremental improvements to be had, leading to fewer loose brackets over time.  This, I hope eveyone can agree, is a good thing for the climbing community.

Thank you all.

-S.Neoh

"You have to decide to do a flag, where you can broke your vertebrae or a barn door depending of your pro" - the poster formerly known as Champ

Offline tradmanclimbz

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Re: Why do hanger brackets get loose over time?
« Reply #1 on: November 02, 2009, 09:32:48 pm »
Those dimples don't do squat. they are not agressive enough. INMOP the #1 reason that hangers loosen up is from lowering. the draws get pulled up in a twisting motion and spin the hanger loosening the nut.

Offline Admin Al

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Re: Why do hanger brackets get loose over time?
« Reply #2 on: November 02, 2009, 11:40:25 pm »
why aren't there lock washers on bolts? wouldn't that help? or the kind of nuts with the Bakelite or whatever in them that keep them from loosening.
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Offline tradmanclimbz

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Re: Why do hanger brackets get loose over time?
« Reply #3 on: November 03, 2009, 12:34:19 am »
The nuts with the plastic  locking stuff on the inside? Wonder if that would last as long as needed? Bolts stay in service 50years etc....

Offline M_Sprague

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Re: Why do hanger brackets get loose over time?
« Reply #4 on: November 03, 2009, 03:02:02 am »
I agree that bolts loosen up from having the hangers twisted around. The rock then breaks down a little and it becomes looser.

It is my understanding that applying a layer of epoxy or other weather sealant between the hanger and rock is not a good idea with porous rock like sandstone and schist. It acts to hold moisture inside the bolt hole, and therefore hastens deterioration. I think the dimples on the Fixe hangers do help a little, if the placement is otherwise sound, meaning good quality rock and against a flat surface.

Glue-ins eliminate the loosening problem and can actually blend in better if set well, but they have there own issues. They are a disaster if you make a mistake and put it in the wrong place, being a  lot harder to remove, and if placed badly they can look horrible. I basically use glue-ins for an area that is going to get a lot of traffic and where the stone is softer, like Rumney, and use stainless steel 1/2 inch expansion bolts in hard rock like granite.

I think they should use glue-in eyebolts more at The Red, as long as they really know what they are doing, the only problem being there that some of the rock is so crumbly that holds break off and clipping holds might change (in which case, does there really need to be a route there? or clean it better before bolting). If not glue-ins, I would go with long 1/2 inch SS. If I ever put a route up there it will be with 6 inch x 1/2 glue-in eyebolts, countersunk and painted.
I suspect part of the reason for less use of glue-ins at The Red is laziness. It takes a lot of time and work to put up a route on steep chossy overhanging rock. To use glue-ins you would first have to place a bunch of cheap, short , removable work bolts to hold you in while cleaning the route on TR and figuring and placing the glue-ins. Then you have to remove them all and patch well so the holes wouldn't be visible.
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Offline sneoh

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Re: Why do hanger brackets get loose over time?
« Reply #5 on: November 03, 2009, 08:34:03 am »

Thank you all for the responses thus far.

I believe 'twisting' happens whenever the direction of the force applied to hanger does not go directly through the center of the bolt and the point where a carabiner or rope "engages" the hanger.  This can happen in many situations, incl on top-anchors of 1-pitch sport routes (which, in theory, should not be subjected to any upward pull).

With the kind of fastener arrangement that requires the bolter to tighten a nut, rather than a bolt, onto a hanger bracket (e.g. the problematic hanger on Flesh For Lulu), will a second, low-profile nut made of the same metal (to avoid possible galvanic action) help?  If so, there is the delicate matter of the amount of torque to tighten this second nut to. And, what about simply a lock or spring washer (again, made of the same metal) between the nut (or bolt-head) and the hanger?

Mark, there are more and more glue-ins sprouting up down at RRG.  I think bolters down there are aware of the advantages (and disadvantages) of glue-ins.  So far, their placements have been quite selective, as far as I can tell.   As you said, with steep routes, temporary, mechanical bolts will be needed so that the bolter can install the glue-ins.  But I have read more than once that some of these temporary "work" bolts were not removed afterwards, leading to confusion and incorrect "bolt count" for the route.


"You have to decide to do a flag, where you can broke your vertebrae or a barn door depending of your pro" - the poster formerly known as Champ

Offline strandman

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Re: Why do hanger brackets get loose over time?
« Reply #6 on: November 03, 2009, 09:31:48 am »
On rock like Cathedral, which is a little nubbly, you NEED to flatten the area for the hanger. Almost no one does this yet I think it is essential. Create a smooth surface and also reduce the likeleyhood of any cracking. I agree the "dimples" don't do shit,you want the opposite, smooth.
The problem with rotation from lowering too can be helped by putting the bolts in a slightly offset vertical orientation rather than side by side,way better. Side by side torques the bolt and the hanger to much, especially when done "death triangle style"

Offline bmbuffy

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Re: Why do hanger brackets get loose over time?
« Reply #7 on: November 03, 2009, 09:58:48 pm »
"ROCK CLIMBING IS DANGEROUS"!!!!!!!!!!!

Offline Multiades

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Re: Why do hanger brackets get loose over time?
« Reply #8 on: November 06, 2009, 07:16:46 pm »
Is this just an issue with loosening of the nut? If so, it should be pretty easy to solve.

From what I have seen, mechanical lock washers are ineffective. Polymer threadlockers (such as Locktite) are probably the best thing to use.

A cool video that gives a fairly illuminating view of bolt torque and tension after stress-cycling:

http://www.youtube.com/watch?v=mgwmuZuJ02I&feature=player_embedded

It's long, but worth watching at least half of it. They use vibration to simulate stress cycling, but I'm sure use of bolt hangers has the same effect over time. I don't think that product is the best solution for climbing bolts, but see no reason not to use Loctite if threads can be cleaned with alcohol, acetone, etc before use. Has anyone tried this?

-Chris

Offline strandman

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Re: Why do hanger brackets get loose over time?
« Reply #9 on: November 06, 2009, 08:02:23 pm »
It's not always the nut. Even with buttonheads, placed well, the rock underneath cracks and flattens out. Torqueing on the hanger breaks the rock underneath and the nut may still be tight.

Offline sneoh

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Re: Why do hanger brackets get loose over time?
« Reply #10 on: November 06, 2009, 08:19:44 pm »
Chris,
The prevailing belief is a hanger bracket gets loose because of torque on the bolt whenever the direction of the force applied to hanger does not go directly through the center of the bolt and the point where a carabiner or rope "engages" the hanger.  This can happen in many situations, as I had mentioned in an earlier post.  And the torque can, in turn, cause the rock behind the bracket to break down, as Mark and John have indicated in their posts.

I have read advice to put Locktite or similar product on the threads of quick-links, part of an anchor system.  But, I have never seen advice to put Locktite on threads of bolts that hold the hangers in place, against the rock. Perhaps experienced bolters can comment on this point.  I am also wondering if Locktite will break down after exposure to the elements for a number of years.  In any case, I do not believe Locktite will decrease the torque on the hanger, and hence the bolt, in the event of a fall.

-S.Neoh


"You have to decide to do a flag, where you can broke your vertebrae or a barn door depending of your pro" - the poster formerly known as Champ

Offline cjdrover

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Re: Why do hanger brackets get loose over time?
« Reply #11 on: November 11, 2009, 10:57:22 pm »
I'm going to venture a slightly-educated guess here and propose that temperature cycling is partially responsible. I work in a lab where we subject a variety of materials to temperature cycles and some of the pressure vessels come out of the oven with substantially loosened nuts, even when used with lock washers. As temperature increases metal imperceptibly expands, and unless the temperature increases completely uniformly throughout the piece of hardware (NEVER happens), the effect of things expanding and contracting at different rates is to loosen them.

Let me reiterate that I have no evidence whatsoever that this is the case with climbing bolts and hangers - it's just a thought.

Offline strandman

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Re: Why do hanger brackets get loose over time?
« Reply #12 on: November 12, 2009, 09:24:06 am »
I'm sure that temp cycling must have some effect on bolts/hangers. I'm not sure about the real effects though unless you also factor in water and ice. Some people used to caulk/epoxy bolts a long time ago and in addition to being ugly, unless done perfectly, water will get in the hole and make things worse.

Offline sneoh

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Re: Why do hanger brackets get loose over time?
« Reply #13 on: November 12, 2009, 11:40:33 am »

In this case, I agree that freeze/thaw cycle due to temp changes is likely to have a greater impact than temp changes w/o freeze/thaw.


"You have to decide to do a flag, where you can broke your vertebrae or a barn door depending of your pro" - the poster formerly known as Champ

Offline tradmanclimbz

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Re: Why do hanger brackets get loose over time?
« Reply #14 on: November 12, 2009, 05:14:14 pm »
judgeing from the areas that I maintain, freeze thaw has jack to do with modern bolts spinning. The bolts that see a lot of top ropeing and lowering loosen up and spin where   the bolts on climbs that get rapped instead of lowered or simply don't get much traffic stay tight.