Thoughts on "Triaxial loading of a belay loop, waist belt, leg loops"?

Like ConorCaroll says it´s biaxial, I´d call it planar biaxial though to define it is in a single plane. But that´s engineering, for climbers it´s still easier to call it triaxial  

Jim Titt wrote:

Like ConorCaroll says it´s biaxial, I´d call it planar biaxial though to define it is in a single plane. But that´s engineering, for climbers it´s still easier to call it triaxial  

Don't the two axes define a plane, so biaxial loading has to be "planar"?

We should rename it to "trivector loading".

Kedron Silsbee wrote:

Don't the two axes define a plane, so biaxial loading has to be "planar"?

There´s all that stuff with torsion in columns that I don´t understand either but that´s probably why planar is used.

rocknice2 wrote:

We should rename it to "trivector loading".

It was just "three-way loading" until someone decided to fancy it up a bit.

Jim Titt wrote:

It was just "three-way loading" until someone decided to fancy it up a bit.

Truth.

Regardless of what you call it, loads applied to a biner via three slings/cables/etc will always be in a single plane.  This has become just the kind of pedantic argument that MP needs!

Maybe some of you think triaxial loading requires physical axials but that isn't what it means (when talking about biners and climbing). All it really means for triaxial loading of a biner is that it is being pulled based on the setup in 3 directions. It isn't talking about x, y, z. Sorry if you don't like the way it is used.

Lets say the bottom of the picture is south and the top is north. So for that picture A = South, B = Northwest, and C = Northeast. This is what people mean when they say triaxial loading for a biner. Sorry if you don't like the name because it doesn't mean x, y, and z physical dimensions. This all comes back to how the biners are designed to be pulled based on the picture to be loaded North and South. So when you add the pull in 3 directions it starts to partly cross load them which is weaker for the biner.

Here are your 3 non-physical directional single plane axials!.

Semantics aside, with forces applied in three directions in the same plane as in the BD diagram, doesn't this essentially replicate the force of the the European/American death triangle on the carabiner (in place of the sling)?  As someone without a background in engineering, I ask this purely from a curiosity standpoint.

Hmmm. So, a pull in the ideal way, AC, or north south, as you call it, is how many axes?

There is no z if it is in a single plane.  Just good ol x and y. 

But, I like your explanation. It reminds me of a kid caught red handed steeling some candy.  “I was walking in one direction. My foot slipped in another, and somehow the Snickers fell in a third direction and ended up in my pocket.  I don’t know how it happened though dad?”  So cute. 

NRobl wrote:

Semantics aside, with forces applied in three directions in the same plane as in the BD diagram, doesn't this essentially replicate the force of the the European/American death triangle on the carabiner (in place of the sling)?  As someone without a background in engineering, I ask this purely from a curiosity standpoint.

Sure. The implication of this is that the upper points are each getting signif. more than half of the load from point A.

30 extra posts because someone forgot to list their assumptions while defining the problem statement.  But at least we got the assumptions figured out.

Daniel T wrote:

30 extra posts because someone forgot to list their assumptions while defining the problem statement.  But at least we got the assumptions figured out.

It has nothing to do with assumptions.  It is technically a misnomer that I was trying to correct.  Of course, part of being an engineer is that I have to overcome my social ineptness through trial and error.  My lesson has been learned.... Now off to find that thread stating friction is dependent on surface area contact.... 

Greg D wrote:

The real question is why the hell are you using a daisy in the gym?

Yup that's also my main take-away here....

And also why would you even consider girth-hitching through the leg loop? Seems to me you only' lowering the point of force, therefore making it a less comfortable/stable position, for a pretty artificial gain in "safety" compared to belay/tie-in loops which are already rated more than sufficient for this tasks.

If you don't trust the belay loop alone to lower/belay pretty much statically with the auto-belay (hard to image a hard fall on auto-belay?), why would you trust it to take leader falls/lower people in the first place? Seems inconsistant to me - you either trust it completely or you don't trust it at all.

A PAS in a gym????? 

I do not normally use one, but when I do it’s tied into the top tie in point only. I find that while hanging this keeps the bottom tie in point down low, the belay loop slack, so you can clip several lockers into it without any problems. 

But most importantly, if I clip a locker or a PAS through the bottom and the top points (back up for belay loop) my manhood gets squeezed hard by the “tri-axial” loading. 

Anybody remember the Willians Harnes? 

Added new meaning to “The Leader must not fall”

Greg D wrote:

Hmmm. So, a pull in the ideal way, AC, or north south, as you call it, is how many axes?

There is no z if it is in a single plane.  Just good ol x and y. 

But, I like your explanation. It reminds me of a kid caught red handed steeling some candy.  “I was walking in one direction. My foot slipped in another, and somehow the Snickers fell in a third direction and ended up in my pocket.  I don’t know how it happened though dad?”  So cute. 

The general definition of an axis is "an imaginary line around which a body rotates". You can have multiple axis on the same plane according to that one and they are not equivalent.

The mathematical one is "a fixed line of reference for the measurement of coordinates". So if you're taking cartesian coordinates, then yes you can only have 2 per axis.

From a vector perspective, yes you can always decompose 3 vectors into X,Y components and get 2 vectors pulling along 2 axis. However, from a climbing gear perspective, those 2 vectors are NOT equivalent to the original 3 vectors, because the point at which the force is applied matters. Meaning you can't move the position of the vector on the plane, therefore you can't decompose it into 2 axis only. Therefore, while not very mathematical, the way it is used in climbing does make sense.

Greg D wrote:

Hmmm. So, a pull in the ideal way, AC, or north south, as you call it, is how many axes?

There is no z if it is in a single plane.  Just good ol x and y. 

But, I like your explanation. It reminds me of a kid caught red handed steeling some candy.  “I was walking in one direction. My foot slipped in another, and somehow the Snickers fell in a third direction and ended up in my pocket.  I don’t know how it happened though dad?”  So cute. 

Yup, it´s a pain in the ass when you remove one of the loads because then it´s bi-axial and then remove the last one and it´s an axial load even though there´s no load at all  

Jim Titt wrote:

Yup, it´s a pain in the ass when you remove one of the loads because then it´s bi-axial and then remove the last one and it´s an axial load even though there´s no load at all  

Nicely done. 

This is the thread that is going to help me break into 5.12 climbing, without a doubt!

Looks like Petzl is calling it "multidirectional" loading: https://www.petzl.com/NL/en/Sport/Examples-of-dangerous-carabiner-loading-