Rigging anchors for balanced load

hi I'm Rob string it from High Point access and rescue in this video we're going to cover anchor angles we're going to look at the relationship between the angle and the loadings back on to the anchors okay so what we've got is we've got a hundred kilogram mass down here at 100 kilograms is connected through a series of connectors into an S type load cell or an S type load cell there which is connected with a wire back to an indicator so only our indicator panel we read 100 kilograms let's just written the mast down the bottom okay so I'm going to lower this mast down I'm going to put it on to two separate anchor points so we're gonna hoist the mass into place so we've got 100 kilogram load coming up through a focal point up to two separate anchors and a load cell on each anchor so first things first we need to estimate what this angle is now there's a few methods that people use to make that estimation one is the this method so you hold two fingers up like that and that's pretty much though that angle inside there so that's that's roughly 30 degrees drummond so that angles 30 degrees you can get iPhone apps and all sorts of things to try and measure that accurately but some down in this region it doesn't matter this there can be a bit of variance in there and it's not going to change much up in there as loading which I'm going to show you thirty degrees and you'll notice on this cell we got 52 on this cell we got 51 so it's pretty close to 50% so we're gonna put this on a chart so as we go through we're going to mark this on a chart so degrees along the bottom the degrees refers to this angle inside here yeah and up here on the y-axis we've got our percentage of load so percentage of actual load there so we've got a 100 kilogram mass which makes this easy okay so what we're saying is at 30 degrees we've got 50 percent of the load on each anchor so now we've got we've got a 60 degree or pretty close to a 60 degree angle again there's a few methods of estimating that one is this so people put their hand up there like that and think well that's pretty close to 60 is there another method what we've got if we take this length from the focal point to the one anchor and if it's the same distance across the top and the same distance down this side we've got ourselves an equilateral triangle so in an equilateral triangle if all sides are equal all angles must be equal which means that this angle must be 60 degrees okay 57 there 57.5 there well that's around that we're going to round that to 60 so 60 degrees equals 60 percent nice and easy to remember okay we've got a 90 degree internal angle a few methods of estimating that one is this so that that angle between those 90 degrees pretty close to it I can use a smartphone to do that so if I place the smartphone there I know the corner of of smartphones 90 degrees I could use a pad or a book or any any object that's got a right angle corners gives us 90 degrees so it's pretty easy to ask to make that one so 90 degrees there we have a look on a load cell on one side we've got sixty nine point five over here we've got 69 point five so they're exactly the same and they're roughly 70% so estimate for the board here at 90 degrees we've got 70% of the load on each anchor let's let's have a look at the mr. blue the charlie we went from 30 degrees all the way up to 90 degrees so there's a difference there of 60 degrees what they did was that changed our load from 50 percent up to 70 percent so there was only a 20% change in load with a 60 degree change in angle I think that's quite significant so we've just pumped this up to 120 degrees as a few methods of working out 120 degrees but accuracy diminishes the higher we get one method is this so people put their hands up there like that I think well that's 120 degrees there's not very accurate though okay the other one is if you're if you stand back and look at it this angle here should equal that angle which should also he call that angle again that's difficult to do without some sort of protractor but there's a bit of a bit of an eyeball you can see that that angle equals that angle equals that angle so for angles are equal out of three there must be a hundred and twenty degrees in it in each angle so let's put that up there 120 degrees if we look at the loading on that if all angles are equal all loads must also be equal so with 100 kilograms here we must have close to 100 kilograms on each of these so you see there's 97 up there and there's 98 up here so it's pretty close to the 100 each side okay so let's put that on the board 120 degrees 100% of the load so it should be a bit of a caution happening there because now whatever's here is also there and it stands to reason that if we increase that beyond 120 degrees the load on the anchor is going to be more than what's on here so we're going to prove that as we go through okay 150 degrees now now 150 degrees is very difficult to pick you're going to need a smartphone or some protractor or something to establish that that's actually a hundred and fifty degrees it's it's a bit hard to use a rule of thumb so 150 degrees up there now you'll see it 150 degrees there but over 190 kilograms on each each anchor which is sort of what we were expecting hundred kilograms here 191 191 so let's put that on the graph 150 190 let's call it 200 200 a nice even number now the issue comes here that there's a this is inaccurate I can't I can't judge that easy and the error here creates a big difference up there so I'm gonna I'm gonna make a slight change to this I'm gonna move this down one peg okay so I'm going to go from 152 152 degrees we want to measure what happens on that on the load cells when I'll make that 2 degree change so at the moment we're reading 191 9 0 okay so we went from 152 152 degrees we also went from 190 to 215 kilograms so an increase of 2 degrees gave us a 25% increase in loading that Manu changed now I can't see the difference between 150 152 I'm flat-out seeing the difference between 150 and a hundred and 60 visually on an anchor system so that tiny little difference makes a big difference in loading up here okay so the graph when we graph this thing actually what put in a few other numbers as a rough estimate 160 is 300 165 is 400 so you can see that that's a very steep ramp as we leave 120 degrees so let's put a curve in here it starts here at 50 it's way up there okay so let's have a let's draw some assumptions in here I'm gonna start with the Green Zone so the green zones a good zone and I'm gonna say between 30 and 90 here's a green zone green for go I'm gonna say between 90 and 120 is a cautionary zone you have to be very mindful that once you go over 90 you're starting to get more and more load on the inka once you get to 120 whatever's on the load whatever the load is that's on each of those anchors and once you go beyond 120 I'm gonna paint that red so we're gonna paint that red because that's so that's what we consider a fairly dangerous area now I'm not saying you can't rig stuff with that in there because we we do that quite often if you look at high lines and things like that and sometimes you do offsets that that you've got quite a tight angle inside there what I'm telling you is once you get into this red zone you've got to know the physics behind it you've got to know some other ways of managing how to establish what those angles are and ultimately what the loads are okay so our first rule of thumb I'm gonna give you first rule of thumb is keep the angle between 30 and 90 degrees okay so we're back to 90 degrees I just want to point out a few components that we've got here we call this blue line or in this case this is our load line load line comes into a focal point and from there we've got our anchor legs back to the anchor points in this case through the load cells I'm gonna add this sling here to demonstrate what we call a projected load line if I pull that up tight just imagine that this is the load line and it runs up and we project that through here this imaginary line that we're putting in place this Dyneema sling so it's our projected load line and you'll notice that the projected in this case by sex that angle which means it splits it in two okay so we've got 90 degree angle there this one comes through the middle so ii tell you we've got 45 on each side okay and in that case we've got balanced load i've got 69 kgs 69 kgs now what i'm going to do is onna radically shift this load sideways we're going to shift it across sideways we're gonna see what effect that has on the loading so I'm gonna shift that across sideways let's look at where this projected load line ends up it should end up somewhere there so we've got a nice straight line now your so you'll see that the projected load line now is closer to this sling that it is to that now the effect up on the anchors is this one's gone down this one went from 70 down to 58 this one is gone from 70 up to 76 so any time when the projected load line doesn't bisect the angle we're going to have different loads on each anchor okay so I'm going to bring that back to the middle that's gonna hang normal project the load line should be somewhere about there so that should be a straight line and these things should balance 69 69 go s so a second rule of thumb the first rule of thumb was keep the angles between 30 and 90 the second rule of thumb is to keep this projected load line bisecting the angle now you might be looking at the chart thinking what's the go with this little box down here what's the go with this angle between 0 and 30 well I want to talk about that specifically a lot of organizations have a system where they talk about anchors and they say there's an eye a Y and a T okay so I would be these angles nice and tight so down in here and they say I stands for ideal Y is what we've got here such sheets of white boy shape and Y stands for yes so yes you can use it t is when they're really tight like that you up in this angle up in this area and they suggest he stands for terrible Alanna challenge the eye on a challenge and I'm going to put some cautionary notes about having angles nice and tight okay so we're going to drop this slide down bring that back in okay so I've dropped this angle back to close to 10 degrees and if you look at 10 degrees it looks pretty good I've got 50 point 5 and 50 so 5050 that and that sort of matches up here zero degrees it's 50/50 it all sounds good the problem comes though when I have a slight shift in the load so I'm going to move that slightly probably only three or four inches or 7080 hundred millimeters we're gonna see what happens to that so essentially when I shift that there I shift that projected load line back over closer to this one it's just very difficult to see over there I've now got I've gone from 50 back to 25 so of harvard's a load on that one I've gone from 50 up to 70 2.5 there with a very little shift in this okay so I'm not saying you can't rig stuff down in that tight angle but what I'm suggesting to you is you've got to be very cautious with it to ensure that our load doesn't move and that we balance the load evenly between these two strands if it is that you're gonna try and make a load cheering anchor okay so we're back out to sixty degrees now and I've put the projected load line in there so just remember the two rules of thumb keep the angles between 30 and 90 make sure the projected load line bisects that angle I just want to make a couple of acknowledgments the first one is this sheet over on the side here I pinched this chart from wreath on I watched him present a chart in one of his courses where he had degrees and he had percent there and he put this line in didn't have the shaded section underneath but he put the line in there I looked around the room and I saw a lot of people understood it they the penny dropped so to speak so you know pinch that off read thanks for that a few other things about five years ago back in our 8:09 we bought some load cells so we bought all these load cells to use in training they had clunky rows joints on them which were difficult to use and a bit cumbersome so the first time we did is we pulled apart a rock exotica omni block and we put the components either side of a load cell so now we can run a rope through that we can measure the actual magnitude of that resultant force through their back through an indicator which work pretty well the other thing we did was we married up and I'll laser pointer to the side of it so I can put a green dot that indicates the direction of that resultant force so not only can I do magnitude of the force I can do direction of the force with that it's a really good learning tool within a year after that I ring rock Thompson up from Rock exotica told him what we were doing and he sent me out so he sent me out some swivel vina carabiners and some of the buckets from the from the pulleys and a machinist a local machinist Ogata and Roussel manovich he made up the fittings to join them all together onto a load cell so that's what you see there the latest addition to the load cell group is this one so Andrew machined up a few fittings for me to put an S type load cell into a leg so this represents a vortex leg or any of the type of high directional leg and we can measure the compressive force down there so it just gives a negative indication on the indicator of force so we can set this up inside our black frame here we can put different angles back to the frame different angles to the load and we can demonstrate what those might what minor changes in their give as a result in force down the pole and back to the guys and anchors okay so that's available we got time for today thanks for watching

Channel: Rope Rigging Academy

Views: 147,395

Rating: 4.9419141 out of 5

Keywords: Rigging, Rope access, Rope, Anchor, Sling, Load, force, Load cell, Force, Angle, Highpoint, Rescue, Highline, Stage, Rock Exotica, Experiment, Outdoor, Caving, Laboratory, Abseil, Rock climbing

Id: X0SP85S1m4Q

Length: 17min 20sec (1040 seconds)

Published: Mon Jan 27 2014

Reddit Comments

[u/yoinker]

tl;dw

https://www.youtube.com/watch?v=aQsn1MZx-hs

[u/uskrewed]

tl;dw Keep anchors less than 90 degrees

Did anyone have any concerns that the anchors weren't self equalizing? I feel like his demonstration of the anchors at 15 degrees (or his projected load line in general) would have been moot if they were.

[u/Kamesod]

Just robbed a familiar infographic out of John Long and Bob Gaines' "Climbing Anchors" guide to simplify this video for y'all. Hope this helps.

http://i.imgur.com/wLnGCZl.jpg

[u/PM_ME_YOUR_PAIN_GURL]

I love the faces he makes and the way he regards measuring with fingers