RRC Archives

weber wrote:

drifter wrote:I'm curious to see the results of actual live dynamic falls.

Concerning what tomdarch wrote, 20Kn falls { 2000 daN (4400 lb)} are not regular occurances...

Let's hope so. Powers and Dynabolt Golds fail when radially loaded (perpendicular to the long. axis of the bolt) in this force range. Ours have been losing their heads in the mid 4000's.

Rick

Exactly - those 20Kn forces are a basis for doing the structural engineering on an Artificial Climbing Wall. It isn't surprising that they'll be semi-overkill. After all, you don't have the 'excuse' (so to speak) of dealing with natural rock. As a liabilibty issue, you want to design a climbing wall to seriously exceed any possible real-world loading, so that the failure of the wall structure or anchor would never be part of an injury/lawsuit. Plus, as in Eldorado's walls, a lot of wall anchors are field welded onto the structure. Any time you have a human being do something a thousand times, a few of those times are going to be a bit screwed up - best to build in a margin of error at each step in the process.

As for recording the actual forces in a fall - that's really, really freakin' cool! (Add on a high-speed video camera and a black-and-white checkerboard background and you're talking home-made Mythbusters!) I know that the focus would have to be on the loads on the bolt, but if possible, it would be cool to test things like grigri vs. atc, 'jump dynamic' catches vs. 'non-jumping' catches and 'slack belay' vs. 'shortroped'. Hmmm... that's probably what you're talking about when you mention all the variables involved.

Now that I'm thinking about it, I'm sure that you would have no shortage of 'jump test dummies', but you might want to rig up some sort of actual dummy (Buster goes climbing!) to test some of the worst case situations - old, stretched out rope, long fall, short roped by the belayer, who is anchored and using a grigri - for example. I'd guess that a simple sandbag at the end of a rope would make for a reasonable 'dummy'.

Anyway - Rick: you never cease to amaze! Thanks again!

It would take an awful lot to exceed 20kn on a fall, especially on a 1 pitch climb. Primarily this is because of all the give in the system -- the rope stretches, your harness will move, the belayer may move, a little rope sliding thru the ATC or grigri or whatever, even a bit of metal movement from the biners all drastically reduce the load on the fixed equipment.

8)

Came across this abstract: http://www.leeds.ac.uk/sports_science/a ... bauer1.htm
It would be nice to get a copy of the full paper.

tomdarch wrote: it would be cool to test things like grigri vs. atc, .... short roped by the belayer, who is anchored and using a grigri - for example.

Is there that much difference between an ATC and a Gri-Gri?

captain static wrote:Came across this abstract: http://www.leeds.ac.uk/sports_science/a ... bauer1.htm
It would be nice to get a copy of the full paper.

Look at the last line:

The comparison of the belaying devices showed mean peak forces of 2368 N (s = 172.5 N) for the HMS-karabiner, 2197 N (s = 234.0 N) for the figure of eight, and 2083 N (s = 175.7 N) for the Grigri. The difference between HMS-karabiner and Grigri is statistically significant.

The mean peak force was lowest on the Grigri! Especially with the idea that the rope slips a fair amount when belaying with an Eight, it's totally counterinuitive that the peak force at the belay device would be LOWEST with the Grigri!

Maybe it catches quicker and drags the belayer sooner which lowers the force. I wonder if these devices were static when tested?

captain static wrote:Came across this abstract: http://www.leeds.ac.uk/sports_science/a ... bauer1.htm
It would be nice to get a copy of the full paper.

Agreed.

Interesting results. 900 pounds peak force using a GriGri static belaying a climber taking a .375 factor fall. 468 pounds with the same hdw and FF with a dynamic belay.

Take a typical situation that can cause a .375 factor fall -- 50 feet of rope out to a climber who is about 9.5 feet past his last bolt and so takes a about a 19 foot fall. (19/50 = about .375)

Most interesting is the way the test was conducted. The author mentions use of a strain gage to measure the force. This is precisely what we will be doing soon here in our tests. I'm rigging a 10k pound load cell (type S strain gage bridge) to be used both for measuring the force on a climber and the bolt from which he is falling. This instrument will also replace our poor old hydraulic hardware testing machine which bit the dust after doing battle with the FIXE glue-ins.

Note that the force encountered by the bolted hanger will be higher than that experienced by the climber. Both these forces will be measured for various fall factors and climber weights. Not sure how much we want to get into different belaying techniques. Definitely will test various belay devices.

We will add an extra bolt as a backup in the unlikely event that the 10k load cell would fail.

A couple days ago, in a post I asked for someone to volunteer to loan us a portable computer for the tests. This is not necessary now because I recently ordered instrumentation that will record the peak force encountered in the falls. All portable.

Rick

So.... Arnold.... won't be back?

dhoyne wrote:So.... Arnold.... won't be back?

Meet the "Son of Arnold." Actually, we will be using most of the hardware -- all except that messy hydraulic cylinder.

Rick