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I have some older yates screamers that I will take out with me tomorrow and see if a *normal* sport climbing fall will even activate them...

Wes

the lurkist wrote:thanks for your work, Rick. That is a real contribution.
Can you extrapolate those force figures (both the UIAA and your faliure figures) to a falling 180lb/90kg mass falling X ft to genreate those forces? How far a fall is needed to approach those figures?
Hugh

It depends on several factors.

Length of rope between belayer and climber?
Elasticity of the rope used?
Straightness of rope run through the draws?
Softness of the catch?
Type of belay device?
Knots used?
Harnesses used by belayer and climber?
Body mass of the climber?
Anchored or dynamic belay?

Probably the best way to answer is to create several commonly occurring scenarios. I'll run some later.

For now, here's an eye opener from the latest Petzl catalog:

In this example, the belayer is 110 pounds, and the climber is 176 pounds. The leader climbs 9.8 feet above his last draw, which is clipped to a hanger bracket bolted 18 feet above the ground. This creates a fall factor of 0.7. The belayer is pulled up about 6.5 feet by his falling leader. ("Soft" catch?)

The rope sees a shock load of 1575 pounds. The topmost quickdraw sees a force of 1350 pounds. The belayer feels a pull of 450 pounds. And, our leader experiences a force of 900 pounds. (Whew!)

Kinda gut wrenching, but the none of the gear fails. All is well.

Wrong. The leader has just fallen 27.8 feet from his topmost position before being arrested. Unfortunately for him, that was also the distance to the ground.

Rick

Zspider wrote:Interesting results, Rick. Instead of the harder rock that you selected, I would like to hear about the worst case scenario, a bolt in worthless, powdery choss. Unrealistic, I know. We all know there are no bolts placed in rock like that.
Nevertheless...

ZSpider

Boy, ZSpider, what IS the worst case scenario? The route developers here in Muir "analyze" the hardness of the rock simply first by visually inspecting, and then by drilling. If the drill breaks through into a pocket, or if it goes in too easy, they abandon the hole and look for another harder spot. Obviously, this is subjective as hell. This is one good reason for persons who want to learn how to bolt serving apprenticships with experienced route developers.

Even IF a drill enters hard rock and IF no pockets are encountered, a hidden fissure could be present just behind the surface of the rock and coincident with the drilled hole. No amount of visual or tactile observation could find this flaw.

If OSHA ever got involved with rock climbing, it would be the end of our sport!

Rick

Spinners? Disconserting when you encounter a loose hanger bracket, isn't it?

But, it may not be as bad as you think. Our preliminary tests with the bolt puller revealed that the sleeves stayed in the holes as the sleeve bolts dragged the female-threaded cones through the sleeves. A typical 1/2-inch sleeve anchor bolt has a 3/8 dia. bolt with 16 threads per inch. The cone in a Dynabolt Gold sleeve anchor has about 9 threads. In a typical installation, the bolt has been tightened to the cone such that about 6 threads of the bolt extend beyond the cone. That means that even though the hanger is loose, the bolt would have to be unscrewed about 11 full revolutions before the anchor significantly weakens due to insufficient thread engagement (4 threads.)

It is important to note that regardless of how far the bolt is unthreaded, the cone and sleeve(s) remain solidly wedged in the drilled hole.

How solidly wedged? The expansion cone opens the diameter of the sleeve from .49 inch to .62 inch, creating a buldge at the inner end of the bolt. But, isn't the drilled hole is only .50 inch in dia.? Not anymore. The buldge actually exerts so much force on the rock that it pulverizes it and creates a cavity in which the buldge can reside. In our tests, as the bolt was extracted under hydraulic pressure, this buldge pulverized the rock ahead of it until a point was reached where the rock fractured around the bolt.

No, it is not a good situation to have a spinner, especially if the bolt is totally unthreaded - duh. But, in those cases where the bolt has rotated a turn or two, the anchor is not significantly weaker than if the bolt were fully tightened.

How do you correct a spinner? Simply re-tighten the bolt. But, herein lies the potential danger. Just how many turns can it be tightened before the expansion cone is drawn so far forward through the sleeve(s) that it causes a tensile fracture of the rock surrounding the sleeve bolt? Our preliminary tests showed that when a bolt was pulled about 1.4 inches out, the rock could rupture, rendering the anchor useless. That equates to 22 revolutions of a 3/8-16 bolt.

Unfortunately, there is no way to monitor how far a bolt has been tightened (and retightened) and consequently where the expansion cone lies in relation to the surface of the rock face.

In Muir Valley, we would very much appreciate it if you would inform us of any spinners you may encounter. We will try (within reason) to keep track of potentially problem bolts and replace and/or relocate them if necessary. If you take it upon yourself to retighten a spinning bolt, please let us know the bolt's location and details of your corrective action.

Rick

the lurkist wrote:Can you extrapolate those force figures (both the UIAA and your faliure figures) to a falling 180lb/90kg mass falling X ft to genreate those forces? How far a fall is needed to approach those figures?
Hugh

I've been trying to find the answer to this question since I started to lead, but the only answer anyone would give me is that it depends on too many factors to get a number. I got sick of that and crunched some numbers myself after making some assumptions about a worst case scenario. I sent all this to my math and physics guru for checking since my skills are just a smidge rusty. If anyone else really knows newtonian physics and wants to get the preliminary results in exchange for actually checking my equations, drop me a pm.

marathonmedic wrote:

the lurkist wrote:Can you extrapolate those force figures (both the UIAA and your faliure figures) to a falling 180lb/90kg mass falling X ft to genreate those forces? How far a fall is needed to approach those figures?
Hugh

I've been trying to find the answer to this question since I started to lead, but the only answer anyone would give me is that it depends on too many factors to get a number. I got sick of that and crunched some numbers myself after making some assumptions about a worst case scenario. I sent all this to my math and physics guru for checking since my skills are just a smidge rusty. If anyone else really knows newtonian physics and wants to get the preliminary results in exchange for actually checking my equations, drop me a pm.

For me, the only thing I know, is that Iwill never take a fall with a factor of .9999 or higher sport climbing in the red. Probably never many higher then .5-.75.

These are great tests, Rick. But for everyone out there worried about bolts ripping out of the wall, I think you are much greater odds of getting dropped, decking, tightroped, breaking/unclipping a biner, etc. It would super cool to rip some of the older stud-type bolts out. I would think some of those would fail at pretty low pull out.

Wes

"An 8ft. fall on 4ft. of rope produces the same fall factor of a 60ft fall on 30ft of rope. The energy of the longer fall is absorbed by the proportionally longer section of rope."

Here's a great read that everyone should know! It goes through, in detail, a fall on climbing gear and all the forces and factors involved.
http://cyclone.antitech.org/Climbing/In ... dfalls.pdf

Wes wrote:
...But for everyone out there worried about bolts ripping out of the wall, I think you are much greater odds of getting dropped, decking, tightroped, breaking/unclipping a biner, etc. Wes

I totally agree!

Think of the climbs in the Red where failing to clip and falling from the second bolt could result in a decking. Can't blame that on hardware or chossy rock.

Wes

It would super cool to rip some of the older stud-type bolts out. I would think some of those would fail at pretty low pull out.

Wes

We hope to test these stud-type bolts in the future as well as a new adhesive bolt idea I am trying to develop.

Rick

It often amazes me how many routes are bolted in such a way that there are potential ground falls from the 2nd or 3rd bolts. I always thought that the point of having safety bolts was to keep the climber off of the ground... even if the climbing is easy there is the possibility of a hold breaking, an inattentive belayer, a mad wood rat biting your hand, etc.

I totally agree, but for some reason those aren't the sort of things I used to worry about. Now I worry about things like gear placement, belayer, where I am on the climb and stuff, but it used to be all about that bolt.