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Author Topic: Nuts in opposition *Geek Warning*  (Read 453 times)

DLottmann

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Nuts in opposition *Geek Warning*
« on: October 31, 2003, 11:18:51 AM »

How many of you have used this technique, and how often?  In 10 years of climbing I think I may have done it 2 or 3 times.  The reason I starting thinking about it, other than being a total geek, is multiplication of forces.  Nuts in opposition are subject to the same multiplication in force two anchors are subject to if the angle is greater than 90 degrees.  Most instruction books show this method, and the angle usually looks close to 180.  Let's say you set it up and the angle is 170.  This puts 573% more force on each piece.  Since most of these placements are sometimes less than ideal, which is why we think to "make them stronger" by using an opposition nut, we may actuaully be making them weaker... unless it is the only possible gear, I wouldn't use this, and am surpised that not one instructional book mentions this fall-back to opposing nuts.  The book will mention the danger in angles on a two-bolt anchor if your sling is too short, and then suggest an oppositional nut placement two chapters later with no mention of the higher forces placed on the gear and rock...  Anyone want to add to this geek thread?
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Schandy

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Re: Nuts in opposition *Geek Warning*
« Reply #1 on: October 31, 2003, 12:13:10 PM »

I've only fooled around with the technique myself, and would only use it when that is the only solid pro because it takes forever to rig and might not go so smoothley unless at a stance.  As far as I can tell your critique deals with horizontaly opposed pieces, not verticaly opposed.  Using a directionaly to keep a nut weighted, or to protect an anchor from an upward pull shouldn't multiply the forces because the downward force is still being held by the top piece.  I'm no physics whiz, so take it with a huge grain of salt.  
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DLottmann

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Re: Nuts in opposition *Geek Warning*
« Reply #2 on: October 31, 2003, 12:26:41 PM »

Anywhere there is an angle, there is a multiplication of force.  This would definitely happen more often with pieces in a horizontal or diagonal crack.  Interestingly enough I have heard from a reputable source that in multi-pitch gear anchors you should not place an upward-pull-piece below you due to this force.  Better to have one or two multiple-pull pieces in the anchor in front (or slightly above) you.
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drb1215

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Re: Nuts in opposition *Geek Warning*
« Reply #3 on: October 31, 2003, 12:34:39 PM »

DMan, I think you are missing the point of placing nuts in opposition.  It's true that you have forces being multiplied, but only if you pull from the center point between the two nuts.  The reason for placing nuts in opposition is to stop the piece from zippering ( usually occurs on the first piece placed, when the rope going back to the belayer is at such an angle that the rope will exert an upward force on the piece if the leader should fall ).  Nuts in opposition provides a means of making sure that the piece doesn't fall out, from a force that is opposite that of the direction desired to hold a fall.

Dan
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DLottmann

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Re: Nuts in opposition *Geek Warning*
« Reply #4 on: October 31, 2003, 12:55:00 PM »

Dan,

I see that point, but would rather move my belayer closer to the wall, or find a single multi-directional piece.  I guess it's a good tool to know, but doesn't see much use.  Do you use it often, and if so where?

Dave
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Schandy

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Re: Nuts in opposition *Geek Warning*
« Reply #5 on: October 31, 2003, 01:27:01 PM »

If you were to fall, the downward pull would be taken by the top piece.  The bottom piece is just there to keep tension on the top piece so it doesn't pull out.  I don't use it a ton, I instead prefer to place a solid piece in a horizontal as my first piece, which can be considered multi-directional on its own.  The forces are only multiplied when the pull is (in this case) directly away from the rock.  
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MJS

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Re: Nuts in opposition *Geek Warning*
« Reply #6 on: October 31, 2003, 02:31:48 PM »

Many routes in the Gunks with a less than "G" gear rating offer up horizontal cracks before their cruxes.  Placing two opposed nuts in a horizontal is great practice, however, I try to only do it when 1 nut is solid.  The other nut is generally placed to keep the first in position.  Another factor to take into account is the direction of rope travel once past the 2-nut placement, so as to not disturb either placement.

Also, when placing 2 nuts in opposition in a horizontal, I generally try to use a rabbit runner/webolette to equalize them, making sure the hard point is far enough away from the cliff in order to decrease the angle between the 2 pieces.  The trick is to have the 2 pieces relatively close together.

That is all I have to offer on the subject of opposing my nuts.
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tradmanclimbz

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Re: Nuts in opposition *Geek Warning*
« Reply #7 on: October 31, 2003, 05:47:52 PM »

I have been climbing about 20 years and back in the day we used to do that stuff a lot but then I got cams. For years i didn't realy trust them but then I gradualy got comfortable with them and now when I am at all concerned about the directional integrity of a placement I try to place a cam. This is not a cure all but in most situations a cam will be multi directional enough to get the job done (while we are young) ;D Anyone here ever froze their arse off while their partner fiddle F$ked arround  trying to equalize a nest of crappy  flared nuts ::) Plug the cam in and climb on through 8)  
« Last Edit: October 31, 2003, 06:43:48 PM by tradmanclimbz »
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Edge

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Re: Nuts in opposition *Geek Warning*
« Reply #8 on: November 01, 2003, 04:35:01 AM »

I think the only nuts in opposition are in the "De-bolting Thin Air" thread.  According to the front page poll, there are 68 nuts in favor of replacing the anchors, and 44 nuts in opposition....
« Last Edit: November 01, 2003, 07:25:05 AM by Edge »
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tradmanclimbz

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Re: Nuts in opposition *Geek Warning*
« Reply #9 on: November 01, 2003, 06:40:33 AM »

WORD ;D
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