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Ahhh.... the good ol' 60-60-70 triangle! Buy yourself one today! _(offer only good on convex surfaces)_

A good way to think about it is that the anchors must not only support the vertical load, but also the load against each other. One anchor is loading the other horizontally, hence the higher load than 50%

Great video as always! The only way to get a perfect 50/50 load sharing is to have an angle of 0° between the bolts, in every other case the sum of the load on the bolts will be more than 100%. The load multiplication of the death triangle has to do with the top strand being free and allowing the bolts to pull on each other. The numbers from the calculations assume no friction, to get similar results on the dynos as expected you will have to add pulleys on the top angles (not really a real world scenario though...).

In Australia, I was always taught that the ADT was called such because there was no redundancy built in.

When I started climbing at Josh in the late 70's, I learned that the Death Triangle was the typical arrangement of 3 button head bolts, center being higher, with countless loops of sun bleached webbing threaded through them. Often so many webbing loops that you couldn't get anything more through the eye of the bolt. Bolts were commonly all within 2 ft and the webbing was looped in a triangle through all three. It was practice at the time to just connect through the webbing loops without equalizing the anchor at all ( (3:58) picture the loop of webbing around the piranha in the video). Pulling on the longest span of webbing often left the angle at less than 30 deg. which greatly increases the load on all angled legs of the "system". The basic idea being that it was very easy to exceed the ability of the system since all aspects of that system were pretty sketchy to begin with. Manky webbing (albeit a lot of webbing) and 1/4 button head bolts. This did not inspire a lot of confidence. So NOT a myth just a safety tip that has probably outlived its necessity.

Your opening comment about taking F2 falls on American Death Triangles on unsheathed ropes is literally something I think about every time I rig slacklines and then I just say to myself "hmmmm it seems like people have been doing this and been just fine for decades so its probably alright" but this episode is what I have been waiting for all along!!!

You guys are idols of mine. I appreciate how selfless, generous, & absorbed in the science you guys are. I appreciate that you guys live life for fun, but also work hard to improve the fun of others

If you look up crane rigging deductions and theories, it explains in great detail how sling angle changes forces in relation to vertical load. 45 degree angle in sling multiplies force by 1.41 compared to a vertical force. So 1 kn vertical force will produce 1.41( barring strange friction forces in the rig) kn of force.

is it just me or is Bobby like the best Human being ever?

Makes sense that the ADT performs worse than a sliding X with the same masterpoint angle. However, if you only have one sling, you can get a more acute masterpoint angle with the ADT than a sliding X. It would be interesting to compare the ADT to the sliding X if the same length of sling is used, rather than the same masterpoint angle.

Is that a dynamometer in your pocket or are you happy to see me…

Just a note that was never explained in the video: the top side of the triangle will always have lower force than the two other sides due to the friction of the rope/webbing going around the corners at the anchor dynamometers. Each of the readings that are on the top length of the triangle are probably around 70-80% of the force felt on the two sides that are directly pulled. All the math problems we ever did in geometry classes are lies! They (thankfully) removed friction from the problems.

This is obviously more of a warning about vector forces in anchors, but you can also use the vector force multiplication to your advantage. It's a rescue technique that is taught to tower climbers and I've used it when we rigged the 1km in Oregon to pull in just a bit of slack. If you have a rope that is anchored at one end and a casualty on the other end that needs to be lifted slightly before being lowered, you can put your body weight on the tensioned rope and it will lift your casualty up slightly allowing you to detach them from whatever they are weighting before being lowered.

This video reminded me of something I’ve wondered about (and also a possible video idea). I’ve seen AMGA certified KZfaqrs suggesting the use of dedicated top-roping quick-draws with locking carabiners. If you orient them with both spines against the rock will you compromise strength of the dogbone (which would have a 90deg twist)? Note: I believe the benefit of using them in this orientation is to keep the rope away from the rock to prevent it from being pinched or rubbing, thus adding a lot of friction to the system and prematurely wearing your rope. Additionally, since they are both locking quick-draws the concern about the rope unclipping itself is eliminated (barring human error).

Ryan's oww makes him a human torque wrench.

Great explanation of Kilonewtons! A lot of my friends ask me why climbing gear isn’t rated for pounds of force. Knowing that is only as good as knowing the forces you’re generating. Your videos are such a good resource for that! Thanks!

another good and informative video - thank you. Coming from industrial climbing (rope access) my experience is that no matter what you show it will always be picked apart for what is perceived as wrong... instead of oh thats a new way to solve this challenge. Having said that - be sure when building an anchor that you check that your locking carabiners are locked... thank you

The vector chart assumes you have individual legs like a standard anchor. The ADT modifies the angle the anchor is pulling because horizontal leg at the top. When you have an equilateral triangle your strand is 60 degrees from horizontal but the anchor is pulled at 30 degrees (look at the angle the anchor is pulling). That means the anchor feels the force as if the master point is 120 degrees. This totally checks out with the test at 7:27. 2.9kn/2strands * tan(120/2)=2.5kn which is super close to 2.46kn.

Thanks for helping us be less obtuse about our anchors.

Explanation of what's happening with belay setups, starting around @17:00: (For clarity of language, imagine the setup on a wall or rock face instead of on the floor, so that we have a clear "up", "down", "left", and "right".) In the up-down direction, each leg of the triangle IS supporting 1/2 of the force on the static line. But in addition to that, they are also experiencing force in the left-right direction. The belay device is pulling both chains down, but it's also pulling them toward each other. And the angle of the "legs" of the triangle determines exactly how much. You can intuitively understand this if you think about a 50-lb. static load on the end of a rope hanging at your waist level in front of you from a point a few feet above you. If you want the rope to be at an angle instead of straight up-and-down, you can pull sideways on it. The harder you pull sideways, the more of an angle you can put in the rope. If you pull with just a couple of pounds, you will give the rope a slight angle. And if you pull with a whole bunch of force, you can make the rope almost horizontal. As we increase the angle of the rope, the up-down force remains the same - it's just the 50-lb weight. But the left-right force increases. Which means the total force being resisted by the rope is always at least 50-lb., and can be a lot more if we're really pulling it hard sideways. It's the same any time a rope (or chain) is at an angle. It's always resisting force in the up-down direction, and force in the left-right direction. How much exactly is a little more complicated, because trigonometry. If you're super curious and want a quick sanity check in a "death triangle" or anchor situation, you can use the formula below (or consult the cheat sheet at the end of this comment). In a two-anchor situation like at @17:00, the total force on each chain is 1/2 x F x sec(Ø ÷ 2) where F is the force on the line and Ø is the angle the ropes or chains make where they meet. sec is the notation for secant (pronounced see-kuhnt), which is one of the trigonometric functions like sin and cos. So if the angle at the belay device is 90°, the force on each chain is 1/2 x 1.83kN x sec(45°) = 1.294kN. If the angle is 60° (a narrower triangle), then it's 1/2 x 1.83kN x sec(30°) = 1.057kN. If the angle is 120° (a wider triangle), then it's 1/2 x 1.83kN x sec(60°) = 1.83kN. Which means with a wide, 30-30-120 triangle, the total force in each leg of an anchor should be exactly the same as the total load on the line! If the angle is 133°, which is the angle in the setup at @20:42, then the force on each anchor should be 1/2 * 2.16kN * sec(66.5°) = 2.708kN, which is very close to what you found. At 178° (meaning the chains are so far apart they're being pulled just 1° down from directly horizontal), the total force on each anchor would be 1/2 x 1.83kN x sec(89°) = 51.43kN!!!!!!! So don't do that. Obviously, the value of sec(Ø) increases a LOT between 133° and 178°, i.e., when the triangle is super-duper wide, but that's beyond the angle most people would try and get away with. However, this kind of multiple does come into play when calculating the total tension on a slack line. Finally, here is a bit of a cheat sheet for equal-length dual-anchor setups with approximate values: Angle Force on each Anchor ------------------------------------------------ 20° 0.5 x load 60° 0.6 x load 90° 0.7 x load 120° 1 x load 140° 1.5 x load 160° 3 x load 170° 6 x load 176° 15 x load (pretty close to horizontal, like a stiff slack line) 178° 30 x load (nearly horizontal, like hanging something from the middle of a very tight line or chain)

I want Bobby to be 100% again!

Thank you Bobby for talking about sliding x redundancy in the line itself. Hope you get better soon.

American caver. Was always taught that the issue was a lack of redundancy, not force multiplication. Pretty simple rule. If you have two anchor points have two independent loops in your rigging.

This angle stuff is super important if using ice screws.

When you do the "regular" rappelling tests with the rope through the caribiners (with the caribiners touching) - you don't see the force multiplication because the sideways forces from when the regular death triangle has the bolts pull on themselves are "skipped" by the caribiners directly pushing on each other. The rope pulls them together and they transmit the side-to-side forces against each other metal against metal. So you are only left with the more direct vertical forces. The only way to rig the system so the caribiners don't touch is for either for the rappel rope to be rigid between the biners (not a thing) or for the bolts to be farther apart. Essentially - the death triangle only "works" as a death triangle if your anchor legs/bolts can't touch each other

Blake’s hitch drop test. As well as any other arborist climbing nots.

I think the scary part comes with is what happens in one anchor blows and how much force is applied to the remaining anchor

Why is E.T. just hanging out in the background and not helping?

Your angle and type of anchor configuration will affect the amount of load upon your bolts. In the rescue world we typically use two different types of systems the majority of the time for anchors. Either a load distributer or load sharing anchor configuration using webbing, anchor straps and such which would be strapped to our bolts or collection of anchors. The configuration with these two anchor types with the type of angle you use will ultimately effect the load on your bolts. Thanks so much for the awesome info you post, its great to work some of your tests into our trainings.

You have to go pretty extreme to get cosine losses eating up much of your force. At a 30 degree angle (equilateral triangle), you are only weakening the whole thing by around 13.4% on paper. At 45 degrees, so a right triangle, you reduce the strength by 29.3%. That's significant but still allows a decent safety factor. At 60 degrees, you're basically reducing the strength in half. Keep in mind though, that is 120 degrees for the bottom angle on the triangle. In reality, harsh angles are needed for any severe loss of performance.

You guys rock! Just want to point out a practical application of the science here. Ever rap off an anchor with one bomber bolt and one really sketchy one? You might think that the sketchy one just carries half the load but now we know that isn't true. So, what if it fails, causing a sudden extension on the other. Hey! That would be a cool video idea! Chop one leg of the anchor and see how big the load is when you're tied in close then at increasing distances below the anchor. Keep up the good work!

Congratulations, you have unlocked the "Trigonometry" perk!

This video is super educational enough!

The biggest issue is the direction of force vector in an ADT. Bolts or attachment points are usually designed to pulled toward the load, not horizontally toward each other. This can cause failure. Mathematically, force amplification won’t occur until the interior angles are greater than 120. 90 degrees is a good rule of thumb. The angle doesn’t matter on the chain when they are connected across the top. This was a rough one.

Hi, I would love to see different kinds of via feratta kits (also the old friction ones) on the drop test tower.

Nice film! Can yall test ice screws vs v-threds?

Ok as a downrigger in the entertainment business for many years this was a brilliant demonstration of the loading forces. We generally love anything from a 30 to 60 degree angle in a two point hang (called a "bridle" in show vernacular) but may do up to a 90 degree angle if need be. I generally speaking don't like hanging angles above a 100 degrees as they begin to side-load roof trusses in a way that causes them to want to twist towards the direction of the force. Brilliant examination of this very showbusiness related subject. Great stuff! 👍

Very good video. Confirms what I always suspected. ADT isn't so bad, Atleast on bolts. Trad gear a differnt story. Though on nasty alpine routes I've rappelled off many single nut anchors. Fixe rings are standard top anchors for sport routes around here.

It would be pretty cool if you could get a physics teacher to explain the theory and compare it to the empirical data :)

I’m a qualified mountaineer, and commercial rope technician and think your channel is awesome and has definitely added to my knowledge and understanding. At the moment I’m seeing so many American videos on KZfaq or Instagram posted by “rock guides” or so called IFMGA guides, that are doing so many dodgy things and posting them as educational. Such as unequalized, unloaded systems, using dual fixed point bolt anchors but then putting the load on one bolt. Anchor points that include a triangle of death, but in a belaying scenario that could end up shock loaded. It seems, all in the name of speed, lightweight, “innovation”. What is going on with the climbing instructors?

Ryan's ouch is now a unit of measurement 😃

You could use a marlinspike hitch for when you need to pull on the line manually. Wrapping it around your hand and yarding on it is no fun!

Will be impossible to share the load between the two bolts as long as you loop through. Because you will always have the rope pulling towards eachother as well as pulling down.

I like the way you California guys talk. Just the way you said, "Science!" at 16:45 made me think of "Bill & Ted's Excellent Adventure" starring a very young Keanu Reeves. LoL.

I feel that the ADT is a lot more concerning on ice or rock routes where you've placed your own protection as it can pull at less predictable angles as compared to other anchors. I've never been concerned when I'm on well bolted anchors of anything breaking. I have been concerned that trad gear might pop if pulled at an angle other than downward.

Hey! Try the death triangle combined with other common issue: carabiners with open gate. See how hard you need to pull to break an open carabiner on anchor with death triangle.

I would have really liked to see percentage numbers in addition to the raw values in KN. For example the lowest point always sees 100% of the load but the center point saw 40% in this configuration. You guys make such fantastic content. Please keep on keeping on!

As a French guy who has been taught to use the "European death knot" I am curious about the result of the test with that one. And to add a comment on the ADT since that is the subject the death part is really the one you mentioned, there is no redudency and fi you break the sling due to a rock falling on it or rubbing against the rock you go all the way down.

On rewatching, at 17:00 and 21:00, finally the realization that the top horizontal strand of the ADT is totally different from a single, taut strand weighted in the middle, where significant magnification of load is possible. If frictionless pulleys were substituted for biners(which add friction that reduces transfer of load), tension on a continuous strand will be equal all the way around; at each bend, both sides exert the same force, and the angle between determines the single resultant force on that point, as the dynamometers were set up to record. Practically, the triangle 1) makes the effective angle on each side shallower, hence slightly increasing their share of load; 2) the main risk is a cut sling, with no isolation to add redundancy, not so much the risk of the triangle causing failure; 3) the horizontal portion of the rappel rope as run directly through rings, will basically equal the applied load below, no matter what the setup involves; the angles at the respective bolts may change, which can increase the load there, but under rappelling loads, never to a dangerous level. A taut cable between bolts, with a ring midway, is about the only configuration which might magnify loads on the bolts beyond a safe level. Another aside, is that isolating loads from two bolts in a 30-45 degree Vee requires no extra "sliding X" because if one side fails, the shift onto the other side involves a very small pendulum of a foot or so, and drop of just inches; equalization tricks can actually increase the distances and shock, tho still negligible.

Hey ! I'm 2 years late for commenting but I just discovered your channel 😅. Anyway, this stuff is kinda basic for me being a mechanical engineer but I love that you're taking the time to test it all ! I laughed a bit when you thought that when using chains and basically just moving your measurement point you'd get a different result with the same angle ! Anyway, keep it up !

Trigonometry is one hell of a drug.

NOTE!! What is shown at 12:00 is very different from the test setup. There are no force magnifying triangles at 12:00, but the test setup using 1 atc creates a triangle. Force wise the 12:00 setup is just fine.

The reason the force on the bolts will never be half the force at the master point, in the triangle configuration, is because the bolts still have to support the tension on the rope twice. The best case scenario is having the bolts very close together and the master point very far away, and in that setup the tension on the rope will be half of the force at the master point, and the bolts will have that tension pulling in 2 directions 90 degrees apart. Because it's 90 degrees you can just use Pythagoras, square roof of 2 because the forces are equal, so the total force on the bolt is square root of 2 times half the force at the master point, so call it 70%. The angle at which the force on the each bolt is equal to the force at the master point is also a cool geometry problem, but i couldn't do that one in my head

@HowNOTtoHighline if you did that last experiment (the 133 degree one), but with even higher angle (ideally 180 degrees) and with less stretchy material, you should see the forces on bolts to be multiples of your load.

Hey guys I have a few simple rules when setting anchors. I sure you already know this but just to say my thing. FYI I come from a climbing but predominantly industrial background. Anchors should be installed at a minimum of 10 x the diameter of the bolt apart, the further the better thus minimizing the conning effect. If you want to form an equilateral triangle of 60 degrees than all you need is three sides of the same length. Ryan how come you don’t use a jumar to tighten your pulley system instead of your hand? Have you guys come across the Harkin hand winch built for a rope access application? One side gives you a 3:1 mechanical advantage and the 2nd configuration gives you a 10:1 mechanical advantage. Bolts to the ground and is compact and great for compressed (small) mechanical advantage.

The reason the chains take less force is because you do not have the added force from the line between the two bolts. When you make the continuous line into a triangle the bolt points are acting as pulleys and directly loading each other along the top.

No jokes about sharing the load? The climbing community is apparently more grown up than me

Hi can you post a link to the dynamometer? I need one for my job. And other things! Any reply appreciated.

A question about the anchor you build at the end: Doesn't the knot you put in the sling for redundancy prevent it from properly load sharing?

This is first year classical mechanics, applications of newtons laws. If you vary the angle then the force of tension will be different. All you need to know to calculate the forces in terms of that tension is the angles and the kilo newton reading. You can decompose the forces acting on the angled straps summing the x and y components to zero assuming the system is at some point in equilibrium. Then you can set up a system of equations and substitute one of the angled forces in terms of another. Then with this A=T/(cos(theta)tan(theta)+sin(theta)) you can vary the angle and see mathematically what the forces will be without doing this experimentation. If you don't make that assumption then you would need to calculate the acceleration by using the 1D position equation in kinematics. Which is the approach I would use when you do those drop tests

when you visualize the forces in your anchor, it helps to see the forces in between the two bolts, separately from the forces along the axis of pull. So you have a) the axial force through the master point and b) the force between the bolts. The Cosine of the angle, gives you the horizontal force between the two bolts. With that, you can easily see how all the forces add up.

From about 12:00 on, running a rappel rope through two rings that are separate does magnify the loads on each bolt. Ideally, the solution is to have chains long enough to hang down far enough to make a lesser angle - but not have two separate rings, at all. Instead, join the two chains with one or two links, and have the rope run just through that, eliminating the horizontal section of rope altogether. Visualize the chains as two lengths of webbing, and the idea is clear. There is no purpose served by creating rings apart. Once again, modern practices have arisen without thorough considerations of the various consequences, and just because bolts ordinarily are assumed "bombproof" does not mean one should routinely use them in ways that tend to multiply forces.

I don't know what I'm more impressed; your test, or the fact that you have 2 enforcers and 3 more dynamometers.

Not sure if I got it right, but here goes: Assume X is the master point force, Y is each bolt's force, and A is the angle between the lines coming from the master point and going to the bolts. Take the vertical components of the angled lines and add them together. That equals the downward force. 2*Y*cos(A/2)=X The force on each bolt Y = X / (2 * cos (A/2))

just some formula, at 19:20, based on the way you measured angle, the 60 deg, i believe formula would be something like: Per sling load = main_load / ( 1 + cos(angle/2) )

By putting the lfk in all knots reduce the strength Is that acounted for in that configuration?

Can you guys break test non equalized anchors?

Try testing Edelrid's "ADJUSTABLE BELAY STATION SLING", if you can get a hold on that. It should behave kinda like sliding-x.

@9:50 - I checked my local climbing store, but I couldn't find an alien like you've got.

That's a cute angle if I've ever seen one.

can you test the weight limit on a dry treat 9.5 70 meter rope?

Que buen video. Por cierto, espero ver a E.T. volando como dummy de pruebas desde la torre jaja

There's a reason that the tension in the ADT anchors at 60° angles doesn't match up with the sliding X at 60° angles. When you have the equilateral triangle tensioned, if you look at the angles that the anchor point load cells are being pulled at, they are NOT 60° with respect to the master point vertical line, even though the ADT angles themselves are. I suspect that if you set up a sliding X so that the pull angle of the anchor lines are the same as the pull angles of the ADT anchor lines, they would be a much closer match in tension numbers.

Would like to see 2 bolts with a tensioned steel cable between them, then put a carbiner in the middle of that span, clip a rope to it as a toprope point, seen this set up in some areas...

Drop tower ideas - test fall factor more than 2

I have a question, is the point of the sliding X design to help equalized forces on either bolt? If that's the case, when you put a knot into the system to create redundancy don't you lose the equalization factor? maybe I'm missing something about why you'd use a sliding x, or maybe redundancy is more important than equalization? Either way, love the videos!

Top tier content!!✌😁👍

The question is did the “death triangle” come from above or below ground and when. It’s probably old enough to be from the natural fiber era. There is an insert in On Rope about multi-rope anchor angles.

can you test the bermuda death triangle next

The idea that the top of the triangle is experiencing some kind of force greater than the tension in either of the other legs is a bit odd. There's only two points acting on that part of the triangle - the tension in the sling pulling each end out until it's balanced. So the tension in that rope should only be about the same as the tension in any other point of the sling (otherwise, the sling would move through the karabiner at each end until it equalized.) It's only when there's some force acting on the middle of the rope or if a knot was jammed up against one of the points that it could change much. A tip: You can analyze a system of rope or chain *fairly* well by considering each bolt/piece of gear/pulley/karabiner as a point in space, then considering each point separately and drawing the forces on the ropes as vectors pointing in the directions that the ropes travel away from the point. This neglects friction and the weight of the ropes/gear, but in a lot of cases those are negligible (and when they're not, you can add those in, too). If you do this with any of the anchor systems you tested, you'd find that the force on each bolt is not just the force required to hold the climber up, but also some force pulling out to the side because of the angle. That's why you'll never see the load being shared all the way down to 50% unless the bolts are exactly in a vertical line.

Do people not watch these all the way through? I love these videos.

Can you just redo every single test you've ever done, but on the drop tower?

Loved watching this video, but the book “ on rope” ( which has been around since the 80’s) has discussed this in thorough.

Would love to see this with pulleys instead of carabiners at the corners of the triangle.

very interesting tests

Interesting video. I had never considered the vector forces at play here. I always though the American Death Triangle got its name because it has no redundancy.

I wonder what the forces would be for simul rappelling? You wouldn't have the triangle scenario, but rather a rectangle

The triangle basically turns the carabiners into opposing snatch blocks. The middle of the line between them will become the floating anchor point and they will then both multiply any force you put through them.

Hey! Can you you do testing on how to splice/knot Samson Tech-12/Spectra/Amsteel?????? PLEASE

9:00 What a background!

You use two bolts instead of one because bolting material or even the rock could fail through damages from rockfall or vandalims

It will be nice to see these tests on a drop tower

WRT Units: The US Customary/Imperial system is, as usual, confusing. Pounds (lb) are a unit of weight (mass * gravitational acceleration) instead of mass, except for the US customary pound which is defined as exactly 453.59237 grams (mass). Pounds-force (lbf) are a unit of force (mass * total acceleration). There are actually several different types of "pound", used for measuring the weight of different materials. For this, I'm considering only the Avoirdupois pound (the normal one). Otherwise you get weird effects like a (Troy) pound of gold weighing less than an (Avoirdupois) pound of feathers. Slugs are the Imperial unit of mass, but they're almost never used. Instead, the US defined pounds to be a unit of mass, instead of weight as was traditional. In this system Newton's second law isn't F=ma, it's F=ma/g_c, where g_c is 32.174 lb * ft / (lbf * s)^2 In US Civil Engineering there's also the unit kip (thousand pounds-force). 1 kip = 4.44822kN. This is mostly important if you're setting up a climbing gym or similar, since the rated forces the walls and other structural elements can withstand will likely be in kips. In the SI system kilograms are the unit of mass, Newtons are the unit of force (mass * acceleration), and there's no explicit unit of weight. In this system, Newton's second law IS F=ma.

Bridles are useful when you need to mount something somewhere where there is no way you could anchor exactly there.

15:25 lookits like a 5:1 ratio , fer every foot wide, youd want it at least five foot long

TLDR: Still don't use the death triangle because it's stupid, but there are misunderstandings in this video. The only reason there is more force on those bolts is because of the mechanical advantage of having the rope go through both in series. If you connect the rope to each by threading it back to the main anchor like a tight V, it simply splits the force. The assistant guy mentions this at 18:00. It's because the ropes are going through the carabiners separately. There is also another difference which is the velocity of the force. The amount of force being put on the bolts in a death triangle is less velocity than in a V shape which does change the danger factor some. (in a 2:1 mechanical advantage the velocity will be half as much ish) It can't "share the load" unless it is connected to each bolt independently. The reason there is slight loss when doing a very acute angle is because of loss of force in the ropes themselves.

I think you’re not taking into consideration that when you make the triangle you’re making two pulleys that are pulling towards each other multiplying the force. Look up an example where someone uses a winch to pull a vehicle that is stuck off road. If the winch is rated at 12,000 pounds that’s what it can pull. If you take the winch line and take it through a pulley back to the vehicle with the winch on it it pulls double because you’re reeling in 1’ of cable but only moving 6” with nearly twice the force.

TLDR; the results you found were not at all surprising if you add the vector forces produced by each strand and use a bit of trigonometry. In your rappel example, even if you're very far below the anchor so that the angle goes to zero, the ropes make a 90* angle through both bolts, which means each bolt sees a factor of sqrt(2) (or cosin 45*) times the tension on the rope, which is half of the climbers weight. So in that case each bolt sees sqrt(2)/2 or 0.71 x the climbers weight. That's why the anchors don't "share the load", because the connecting segment across the top always adds another component of force that is perpendicular to gravitational pull. By contrast, if you have a very long sliding x (approaching 0 degree angle) both strands on each bolt pull down, so the vector forces are are parallel. In that case each strand carries 1/4 the climbers weight, and each bolt supports two strands, so each bolt supports half of the climbers weight, hence "sharing the load".

When you're climbing on an old route whose bolts are sketchier than poorly placed micro nuts, it surely deserves the name "Death Triangle".