Equalizing anchors.

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WBraun

climber
Feb 11, 2007 - 12:04am PT
No those won't work Ed (Juans detectors).

Ed if you need load cells come see me next time you're here in the Valley and I'll lend you mine.

GOclimb

Trad climber
Boston, MA
Feb 11, 2007 - 12:41am PT
rgold said: In my possibly mistaken reading of Gabe's diagram, the Mooselette appears to have seven bends around biners compared to the five bends around rings in the Geekqualizer. Two of the Mooselette bends are at relatively large angles, in some cases (e.g. the indoor picture posted earlier as opposed to the sketch) so large as to be insignificant, in which case the number of bends could in some cases be effectively as low as 5, the same as the Geekqualizer. However, the Mooselette has three strands interacting and possibly binding at the power point biner, whereas the Geekqualizer has no such interactions.

You're quite right that in the Mooselette, (or any configuration with multiple strands through a power-point) the strands at the power-point biner might bind in a hard fall. I've never seen it happen from bodyweight, perhaps because cord strands tend to sit next to rather than on top of each other, or perhaps because all the strands at the power-point are moving in the same direction, or because only one is moving more than millimiters. But with a harder fall, or with a piece blowing - I don't know, that's beyond the scope of my testing.

As for the number of biners with tight bends, take another look. Of the 6 biners, as you say, two of them are at angles that are probably insignificant, and one of them is completely fixed (due to the limiter knots on the middle strand). So there are really only three biner interactions at high angle. Of those three, there's only one strand/biner that moves much. Do folks think it matters how much cord must move through a biner, or is any movement equivalent?

By the way, the CharlesJMM and the Equalette look like they should be big winners on the friction front, unless the tiny-movement theory redeems the Mooselette.

GO
climbingjones

Trad climber
grass valley,ca
Topic Author's Reply - Feb 11, 2007 - 01:08am PT
WOW! Thanks for all of the posts to this thread. I knew there was some discussion to be had here. Though I must admit that I dont understand all of the equations that have been posted. I still feel that the sliding "W" is the best, for a regular free climbing anchor anyway. Tying a know in the system anywhere just limits the distribution of the load. We know that the belay is always shifting if you, as the belayer, are hanging from it. I feel the slider works constantly to evenly distibute the load. The shock loading of one piece blowing is minimal, in my opinion, since we routinely rely on one piece to arrest a fall of much more distance than the resulting "fall" in the event that one piece blows in the anchor. But, I still respect the opinion of you much more knowledgeable folks in the physics of this situation. Thanks again. Keep it coming to make this the most responded to post I have seen. ;)
murcy

climber
San Fran Cisco
Feb 11, 2007 - 11:50am PT
The solution is in today's SF Chronicle!

rgold

Trad climber
Poughkeepsie, NY
Feb 11, 2007 - 03:12pm PT
I bet Werner's got one of those things for rescue rigging. This just shows how useful climbing gear can be when you open your mind to the full potential of uses.

Back to the Mooselette:

"As for the number of biners with tight bends, take another look. Of the 6 biners...one of them is completely fixed (due to the limiter knots on the middle strand). So there are really only three biner interactions at high angle.

It isn't the number of biners with tight bends that matters for friction, it is the number of tight bends in the system. When I look at the Mooselette diagram, I see three movable strands at the power point biner, one from the left anchor to the lower limiting knot, one from the right anchor to the lower limiting knot, and one from the left anchor to the right anchor. These three strands plus the two bends at the left and right anchor biners make for a total of five friction-inducing bends in the system, as well as whatever effects the binding of the three powerpoint strands produces. Moreover, I wouldn't completely discount the friction contribution made by the other two biners; it depends how you rig the Mooselelette.
GOclimb

Trad climber
Boston, MA
Feb 11, 2007 - 04:41pm PT
Regarding the Mooselette: Yup, three moving strands through the powerpoint. What I'm just not clear on is whether or not it matters how much each strand moves. Because two of those strands move only like a millimeter per foot, and typically in the same direction as the main moving strand.

GO
raymond phule

climber
Feb 12, 2007 - 07:23am PT
Nice rig rgold. It should be easy to use. Friction could definitely be on issue with this and many (all?) 3 piece setups.

"now that we are learning how bad the cordelette is, even with just two equal length arms"

The worst load distribution in the equal length arm test was 39%-61% i.e. the force in one of the arms was never less than 39% of the total force. I dont belive that this is that bad.

I think that it should be interesting to see tests performed for a 3 anchor rig, both static and equalising.

The link you posted suggested that friction playes a large roll in a setup like yours. It is hard to say what happens with a larger load and dynamic case. I think friction plays less of a roll then but I am not sure.
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