http://www.rockclimbing.com/...p.cgi?Detailed=69768

this takes the sliding x with limiter knots and allows it too be redundant and capable of multiple anchors. take a cordalette and loop it in half (or 2 big slings) (the doubling making the cordalette or sling redundant - an issue with most of our other systems)

I have an eye infection

4. A note: The main drawback (really the only drawback according to our testing) with the slinding x (to connect 2 pieces) is that the X sometimes binds on itself (the "clutch" effect), but this in entirely avoided by using an anodized widmouthed biner at the master point. Always use one and the slidng x is just about as good as it gets for use with two pieces--in both vertical and horizontal orientations.

5. Another note: There is little if any evidence of a strand breaking in a rigging system in any real world fall. Providing your gear is in good condition, the concern that a strand might break is a theoretical, not a real world, concern.

Yeah, you'll have to read it all, mostly forst 3 pages. john's research has pretty well debunked the "shock load" thing. Bottom line...statistical evidence says it's no worse than extending the fall by whatever the extension is. IE adding like 1 foot to the fall.

Cracklover, ref. the last anchor pictured in your post of yesterday, 2/20; (the one in front of the door): I've used that anchor set up from time to time, and felt fine about it in the right circumstances. Something to be aware of though, unless there is something above and out of the photo change things, is that when equalized, the left hand piece is taking half the load, with the other half being distributed between the other two pieces. I've used this distribution on purpose when I had one bomber placement and a couple more that didn't inspire as much confidence. You just want to make sure that if you do have a weak piece, it isn't the one that carries the largest load.

Snip

There are other instances of him not mentioning the limiting knots, but if they are unnecessary I doubt he would be including them in his test. I am just looking for some clarification. I suppose it's a matter of degree, as the limiting knots would certainly reduce the forces to some degree, but how much and is it really worth it? Just wondering.
sc

I was going to hold off on making a definitive statement on "Shock Loading" till I had time to work up what Jim at Sterling had actually found from his tests. But since it seems some folks simply can't let the thing go (nor should they till the data's in), here's basically what Jim scribbled down after doing some tests to try and create a shock load in a normal set up with a pretty stout dynamic fall (factor 1--80 kilo load dropped on 10.2 nylon rope connected to a two annchor point equalette).
JL

Here's my problem with this. If the belayer is doing a non redirected belay he/she is potentially being accelorated by the tension the rope to the falling climber in addition to gravity. In effect creating a potentatial higher than factor one fall factor (in terms of the belayers velocity versus amount of rope he's connected to).

When there is a lot of static components in the system, like tech cord and static line, a dynamic load is deceleratd very quickly, meaning the peak loading happens very fast, in a split second. Even moderate loads, when they are caught in this way, can bust the gear apart.

The standard sliding-x becomes redundant the minute you put a limiter knot on each side. You don't need to double it over for this to occur
[and in the very next post...]
Let's separate the breakage issue from the issue of having a cord sliced/crushed. In most cases, I would not be comfortable with an anchor that requires 20 feet of cord which, if it is sliced anywhere along the length, would cause catastrophic failure of the entire anchor. This failure mode is not implausible.

Again, thanks for all your and your team's work on this and I agree this has been one of the best and most useful threads to pass by on RC.com for some time.

I don't see how this could be worse (on the anchor) than if the belay was redirected through the anchor power point.

Regardless, rope slipping through the belay device should mitigate an related problems.

I know you wanted to see math on this but I think John's early testing indicated that many factors mitigate the potential "shock load".

Big mass (belayer) hiting a short lenth of hopefully static material at a relatively fast speed? Basically the question for me is it possible for the belayer to be speed up enough by the falling climber to have what amounts to a high fall factor fall. The answer is neither intuitively or mathmatically obvious to me.
Not neccisarily see above it's mostly about how fast the belayer is traveling not the climber. Rope slippage will provid an upper limit to how fast a falling climber can potentially accelorate a belayer but I still don't know what this value is.

That means the maximum force that any fall can put on the belayer is south of 600 lbf. After that, the rope starts slipping, dispursing the load over time.

Does that clear it up?

JL

All anchor setups should be put through the filters of KISS and SRENE.