Falling on two or more aid pieces combined

Please let me know if there is already a topic on this and sorry if this is a repeat or a dumb question but I was looking to find more information on clipping into two or more aid pieces and falling.  I know if a piece has less than 2-3kn it is not desirable to fall on it but what if you combine two or more microcams/micronuts as a piece of protection and fall on it (assuming you placed them correctly)?  Does the factor force increase?  Just wanted to know the community's thoughts, experiences and other recommendations I may not have thought of.

Thanks in advance!

Edited: wording

there are more factors going into safety of this scenario than just a straight yes or no answer.. (rock quality, how you are placing the pieces, what the pieces are, extension or not.. etc)... why not play around with it yourself and have a solid piece you trust to catch you shortly underneath it in a safe falling distance.  you could take other people's opinions and experience... or your own.

You’d have to clip them in a way to share / distribute the load. One option for 2 pieces could be a sliding x to hopefully “equalize” (they are never really equal).

Sometimes you have to take what you can get.  If you're climbing a route that protects with marginal gear, whether it's a free route or an aid route, chances are that you'd understand that before you leave the ground and have a good discussion with your partner about what you're in for- fall potential, ledges, rope management, and have a "what if."

Alex CV wrote: You’d have to clip them in a way to share / distribute the load. One option for 2 pieces could be a sliding x to hopefully “equalize” (they are never really equal).

This is precisely the original use of the sliding X.

I don't think there is any consistent answer.  Here are some things to consider.

If the two pieces are not horizontally aligned, then any rigging that is meant to share the load will lower the clip-in point and so increase the fall factor, but that increase is so small as to have little or no practical significance.

As Marc mentions, a sliding-X may be worth trying, more so as the leader gets high on the pitch.  Sliding-X behavior has been shown to be unpredictable in testing, so may not confer an effective load distribution, but then again it might.  But note that getting an effective load distribution assumes the two pieces will withstand relatively equal loads.  If this is not the case, distributing the load, having the weaker piece fail and cause a higher load to the better piece because of sliding-X extension, is actually counterproductive.  If a sliding-X is used, all the carabiners involved should perhaps be lockers, as we have relatively recently seen evidence that the chaotic rope dynamics that occur when a piece fails can cause unclipping.

At worst, with two pieces judged to be about the same, you default to the situation in which the two pieces are clipped without trying to distribute the load, albeit with some extra extension from the sliding-X if one of the pieces fails.  With a lot of rope in the system, this extra extension will have little practical effect on the fall factor and so on the peak load to the second piece.  On the other hand, trying the same thing  close to the belay is more questionable, as the extension in a sliding X failure in that case might have a significant effect on the fall factor and so load the remaining piece with more than it would have gotten without trying to distribute the load.

These considerations are complicated by the fact that if two pieces are not equalized, there can be fall energy absorbtion involved in the failure of the first piece, and so the second piece gets less of a load than it would have gotten had it been the only piece involved.  (This is not because there is any significant energy absorbed in the actual extraction of the piece, but rather that the rope stretches some and then snaps back before the second piece is involved.)

The trouble with all this is that there is generally no way to know which of thes scenarios you are facing, so the knowledge of possibilities doesn't end up providing much if anything in the way of guidance, and at the end of the day you do what your gut tells you. Whether an informed gut is better than an ignorant gut isn't clear either.  

Perhaps two vague guidelines do emerge: one is not to try equalizing pieces with a sliding-X that you judge to be quite different in holding power, and the other is that the extension penalty from a sliding-X failure decreases as one gets higher on the pitch---at least if the rope path is not one with a lot of friction.

In view of all these uncertainties, one also has to consider whether the extra time consumed in fiddling for load distribution is ultimately worth it.

I've used sliding Xs on two closely - placed pieces to protect a crux in run outs. long sling tied into a masterpoint is better, as there's no anchor extension if one piece were to pop out, but, you're the leader. It's your lead, your art. Getting advice and doing something just because we said so is no insurance for your survival. 

Paul Hutton wrote: I've used sliding Xs on two closely - placed pieces to protect a crux in run outs. long sling tied into a masterpoint is better, as there's no anchor extension if one piece were to pop out, but, you're the leader. It's your lead, your art. Getting advice and doing something just because we said so is no insurance for your survival. 

No doubt and you described it best that your lead is your art but I'm just looking to hear people's experiences and thoughts/reasoning behind these situations where the route is runout and you're resorted to questionable micro placements.  I feel it's good to at least have some kind of preparation rather than none.

John C wrote:

No doubt and you described it best that your lead is your art but I'm just looking to hear people's experiences and thoughts/reasoning behind these situations where the route is runout and you're resorted to questionable micro placements.  I feel it's good to at least have some kind of preparation rather than none.

If the route is runnout and the gear is marginal then ultimately you have to consider the likelihood of a fall. Efforts to distribute the load or otherwise increase the holding power of marginal pro are unlikely to make a huge difference in reality. All the variables that are practically impossible to assess on lead, and potential to make the problem worse, complicate this situation even further.

Ultimately it comes down to not falling or bailing off the route. If the terrain is well within your abilities and the rock quality is good (low likelihood of breaking off holds) then perhaps it's time to clench the butthole real tight and get down to business. If the terrain is difficult and/or the rock is crappy then you're probably better off bailing. 

In practice this situation probably calls for bailing, but in theory I think a quad-like equalized anchor (e.g. a sling with limiter knots, clipping one of the strands between the knots) would have less of a friction/locking problem than a sliding X.

Serge Smirnov wrote: https://www.mountainproject.com/forum/topic/109787271/equalizing-2-pieces-on-lead
https://www.mountainproject.com/forum/topic/111226119/kn-and-micronuts
https://www.mountainproject.com/forum/topic/112917478/equalizing-two-pieces-vs-clipping-individually

In practice this situation probably calls for bailing, but in theory I think a quad-like equalized anchor (e.g. a sling with limiter knots, clipping one of the strands between the knots) would have less of a friction/locking problem than a sliding X.

Thank you!!! Good links to info I was looking for!!