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Ksolem
Trad climber
Monrovia, California
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Sep 13, 2014 - 02:30pm PT
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such as the masterpoint flipping during a lower
By masterpoint I assume you mean the 'biners the top rope is passing through? That point can flip while loaded up in a lower? I'd have to see that.
Personally if the anchor is two modern bolts in good rock, any setup which is attached to both bolts, is approximately equalized and can't un-clip is bomber. An anchor built with gear for top roping should be 100% bomber as well. If it's not then someone is not competent or your TRing the wrong route.
Belay anchors on routes should be bomber as well, unless the climbers go into that terrain knowingly. In such a case every trick in the book comes into play. First is real expertise in placing gear, never settle for second best.
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apogee
climber
Technically expert, safe belayer, can lead if easy
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Sep 13, 2014 - 05:41pm PT
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"In which case the added security and reduced wear become more important."
Nah...it's really not about the security factor....doubled/opposed would be plenty secure.
As mentioned, it's the larger radius the rope moves across, which tends to run smoother and is less hard on the rope. Seems like a minor detail, but the ease of rope management over the course of the day really makes a difference.
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rgold
Trad climber
Poughkeepsie, NY
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Sep 13, 2014 - 07:30pm PT
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"A scenario of some interest to climbers that Long/Ewing did not consider is what happens in a factor 2 fall onto the belayer if the impact pulls the belayer off."
Maybe they didn't consider what happens in this scenario because...it is obvious...the whole team takes the dirt nap.
There are plenty of "obvious" things that are just plain wrong. I've had to catch a factor 2 fall and one very close to that with the so-called "shock load" horizontal without the party taking even a dirt coffee break. Fortunately, my anchors and the way they were rigged were up to the task.
Long, Gaines, and Ewing were well aware of situations in which factor-2 falls were held and other situations in which the anchor blew and the party was killed, so it is beyond question that this scenario was of "some interest" to them as contributors to a treatise on how not to take that dirt nap. But the test protocol used didn't address this situation and others as well (recall the DAV result mentioned above), and the results were widely misunderstood as saying, universally, that extension doesn't matter.
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Ksolem
Trad climber
Monrovia, California
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Sep 13, 2014 - 07:55pm PT
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So you will be psyched to TR on my sliding x made of dental floss, right? It's self equalizing!
Pardon me. I made the assumption this chat involves people who are discussing the use of climbing gear. ;-0
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Bill Mc Kirgan
Trad climber
Cedar Rapids, Iowa
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Sep 13, 2014 - 08:33pm PT
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Three ovals for the master point is good, but I think 5 might be even better. Has any one tried 5?
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JimT
climber
Munich
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Sep 13, 2014 - 11:43pm PT
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Since you get the same 180 degree bend in the rope (split into two 90 degree bends) and then friction along the top surface, my guess is the three carabiners provide more friction than one in a top-rope setup.
This is so.
Three ovals for the master point is good, but I think 5 might be even better. Has any one tried 5
Sure, Iīve tested up to 7 to see at what point the friction from adding karabiners stops increasing, after 7 itīs not detectable.
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the Fet
climber
Tu-Tok-A-Nu-La
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Sep 14, 2014 - 11:26pm PT
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^^ you've tested this? My guess would be 2 or 3 biners have close to identical friction.
Adding surface area doesn't increase friction. Friction is a function of pressure and the coefficient of friction of the two materials. At least that's what the experiments in physics class taught me. We tested a wide tire vs a skinny tire, exact same friction if the same weight is applied to both.
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Big Mike
Trad climber
BC
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Sep 14, 2014 - 11:50pm PT
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I could see adding a biner dissipating heat a bit better possibly causing less wear!
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bhilden
Trad climber
Mountain View, CA/Boulder, CO
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Sep 15, 2014 - 12:01am PT
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The key factor in choosing the number of carabiners for a TR anchor is not the number but making sure you use ones that are from different manufacturing lots. That's why I only use carabiners with individual serial numbers.
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clinker
Trad climber
Santa Cruz, California
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Sep 15, 2014 - 08:23am PT
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Four bolt anchors at all belays would allow more options.
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RyanD
climber
Squamish
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Sep 15, 2014 - 10:50am PT
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Can't believe nobody has mentioned making revolver quickdraws for Lowering off bolted anchors & TRs. Low friction & makes your rope last forever. You can't oppose 2 of them though because the wheels won't line up properly, causing the bearing to wear out quickly, so most ppl will probably want at least 5 of them on the rope side just to be safe, unless they are reckless n00bs.
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JimT
climber
Munich
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Sep 15, 2014 - 10:54am PT
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Can't believe nobody has mentioned making revolver quickdraws for Lowering off bolted anchors & TRs. Low friction & makes your rope last forever. You can't oppose 2 of them though because the wheels won't line up properly, causing the bearing to wear out quickly, so most ppl will probably want at least 5 of them on the rope side just to be safe, unless they are reckless n00bs.
If you reduce the friction at the top youīll have to increase it at the bottom when you lower someone and wear the rope even faster on your belay plate.
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RyanD
climber
Squamish
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Sep 15, 2014 - 10:55am PT
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Grigri Jim T, but that's for another thread.
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donini
Trad climber
Ouray, Colorado
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Sep 15, 2014 - 10:57am PT
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Overkill is fine and dandy with short climbs and TRs but don't being doing that if you multi pitch with me!
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RyanD
climber
Squamish
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Sep 15, 2014 - 10:58am PT
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Hahah!!
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JimT
climber
Munich
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Sep 15, 2014 - 11:03am PT
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^^ you've tested this? My guess would be 2 or 3 biners have close to identical friction.
Adding surface area doesn't increase friction. Friction is a function of pressure and the coefficient of friction of the two materials. At least that's what the experiments in physics class taught me. We tested a wide tire vs a skinny tire, exact same friction if the same weight is applied to both.
The classic model of friction is really virtually worthless anyway but donīt worry about that. The reason thereīs more resistance over more karabiners is the resistance over a karabiner or whatever is the sum of the force required to bend the rope around the object and the surface friction. Round a biner rope bending is the major resistance and bending, straightening the rope and bending it again takes more force than doing it once. The further apart the bending takes place the straighter the rope is inbetween and so more force is required to bend it again.
Sure Iīve tested it, hereīs the results;-
The caption is a bit confusing as itīs part of something else, basically the lower the force on the left scale the less effort was required to move an 80kg load.
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Moof
Big Wall climber
Orygun
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Sep 15, 2014 - 11:55am PT
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What the heck is your X axis? I am really confused as to what that graph is trying to convey.
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Barbarian
climber
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Sep 15, 2014 - 01:25pm PT
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I looked at the chart and discovered my problem - I keep using blue carabiners. I don't worry about friction. The one's I use are oval ones marked Eiger USA. I've been using them since 1972, and they're really smooth.
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JimT
climber
Munich
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Sep 16, 2014 - 12:08am PT
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What the heck is your X axis? I am really confused as to what that graph is trying to convey.
Like I said, itīs a bit confusing because the captions were related to something else really.
Basically the X axis is the force required to lift an 80kg load using a 2:1 hoist (Z haul) with varying numbers of karabiners at the turning point. Add karabiners and the force required increases i.e the friction increases. There are a number of ways of testing this experimentally and Iīve done most of them, the end result is always the same.
As part of testing lower-offs weīve also tested how what happens if you move two rings apart, the resistance stops measurably increasing at about the equivalent of 7 karabiners.
The Y axis is the pull time in the test rig but itīs left off since its a)irrelevant b)offset for each test otherwise you wouldnīt be able to see anything.
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climbski2
Mountain climber
Anchorage AK, Reno NV
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Sep 16, 2014 - 12:11am PT
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OH jezzus freaking christ..I didnt even read a single post on this thread..
84 posts??
cmon..have we become rcnoob on noob dot com?
here is my advice..not having read a damn thing other than the title
don't fall
oh
YER GUNNA DIE
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