[weber]

Last weekend, I did more strength testing of various bolted hangers. This time, the test apparatus was configured to pull straignt down on a hanger, the way they are normally loaded by a falling climber.

There are more photos and technical info than most readers would want to weed through on this forum, so I'm going to summarize the findings of one type of bolted hanger here. Please keep in mind that this information in no way constitutes a recommendation on how or what to install in rock walls to protect your personal safety while rock climbing. It is merely a reporting of strength testing of a particular installation commonly used in the Red on Corbin sandstone walls.

Results of testing on 4/10/05

The rock wall chosen is located on Muir Valley property adjacent to the footpath leading down from the main parking lot to the Valley floor. It was chosen due to its "marginal" composition. In other words, it is comprised of Corbin sandstone that is softer in composition than most of the rock one finds on bolted climbs in the Red. The hardness of the rock was measured subjectively in the same manner that many route setters use. One merely drills the rock and observes the amount of force needed to advance the drill bit and the consistancy of the material removed by the bit. If the bit advances fast, and the waste material is granular, like sugar, as opposed to fine dust, then the rock is soft. This wall is soft. It took less than 30 seconds to sink a half-inch bit 5 inches into the rock, and the waste material was like granular sugar. Although marginal, I believe that most route developers would agree that the wall I used for these tests would be hard enough for placing anchor bolts for a climbing route. In the near future, we will ask route setters to drill this area and give us their opinion.

Due to the soft nature of the rock, the bolted hangers placed here were considered to constitute a "worse case" scenario.

A 1/2-inch Dynabolt Gold (class 5) sleeve bolt, 3.75 inches long was used to secure a Metolius hanger bracket to the wall with 40 foot-pounds of torque. The standard Dynabolt washer was located between the head of the bolt and the outer face of the hanger bracket. A downward force of 4500 pounds was applied by the hydraulic test apparatus and maintained for ten minutes. This is approximately the UIAA 123 standard limit for rock anchors (20 kiloNewtons).

Although the outer portion of the rock at the bottom of the hole was crushed down almost an inch by the bolt, which bent over about 20 degrees near the outer end, the bolted anchor survived the test and failed only when I cranked up the force to 5040 pounds, at which point the head of the bolt failed in tension.





The Metolius hanger bracket was distorted, but showed no fractures. The lower portion of the bolt, sleeve, and expansion cone remained locked securely in the hole after the test.

The test apparatus remains bolted to the test wall. You can take a closer look at this failed bolt, other failed bolts, and the test gear when you walk by on your way down to the Valley floor. (BTW, this equipment is not booty.)

Rick Weber
_________________
We cannot change the cards we are dealt, just how we play the hand. - Randy Pausch
None are so old as those who have outlived enthusiasm. - Henry David Thoreau

[captain static]

I had been trad leading for a good number of years before sport climbing came on to the scene and I was more afraid to fall on bolts in sandstone than to fall on gear (I must admit that I'm so old school that when I first started climbing, the "leader must not fall" mentality was still prevalent). Now I think I might be able to trust those bolts a little bit more?

Seriously, that type of shear failure is what I would expect. I did the calculations and the design for the top anchors @ Clifton Gorge & anyone who has seen them knows that they are quite stout. After all it was a State job.
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"Be responsible for your actions and sensitive to the concerns of other visitors and land managers. ... Your reward is the opportunity to climb in one of the most beautiful areas in this part of the country." John H. Bronaugh

[dhoyne]

I find this very interesting. It appears then that the rock will slightly yield in compression before a bolt is in danger of breaking (of course this is on soft stone). Do you have plans to find some harder stone (such as found all over in Muir Valley) and do the same test?
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Sarcasm is a tool the weak use to avoid confrontation. People with any balls just outright lie.

[weber]

[dhoyne]

One more question: how loud is the pop when the bolt lets loose? I bet it'll scare the bejeebus out of anyone.
_________________
Sarcasm is a tool the weak use to avoid confrontation. People with any balls just outright lie.

[weber]

[weber]

[Spragwa]

Rick,

I really appreciate all of the testing that you have done. Thank you so much for putting this information up on the site and explaining it so that a simple lay-person can understand that she's safe on the rock. Up til now, I've simply relied upon the Lurkist and another friend of mine to say "hey, that's safe." In fact, my stepdad thinks the Lurkist bolted everything at the Red, therefore, he believes it is safe. LOL. I digress. Thanks for letting us in on the information. It means a great deal.

Morgain
_________________
Jesus only knows that she tries too hard. She's only trying to keep the sky from falling.

-Everlast

[dhoyne]

[weber]

[Horatio Felacio]

hey rick, will you be testing any smaller bolts (3/8" or 1/4")?
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Yo HO!! Just got me a code red and some funyons big dawg!!! SHIT YEAH! - Ray, excited about his breakfast

[weber]

If any of you route developers out there would like a particular piece of hardware tested, please get me a sample. Hugh, Blake, Terry? If you want to test on rock in the MPRP, then you'll have to help carry old Arnold down there.

Rick
_________________
We cannot change the cards we are dealt, just how we play the hand. - Randy Pausch
None are so old as those who have outlived enthusiasm. - Henry David Thoreau

[weber]

[the lurkist]

Is it plausible that the "soft" quality of the corbin sandstone actually acts as a buffer or shock absorber, allowing the bolt to fall back on its tensile qualities as it deforms down as the rock crushes under it?
I saw that Eric's bolt (Triplex by fixe?) faliled at a lower force than the dynobolt gold. Eric's bolt failed in shear force where the dyna bolt gold failed, as you said, in a tensile force.
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... That’s really life. You don’t have a title — you just exist. Some days you have good days; some days your back hurts.
Miguel

[weber]