Angles, Redirects, & Forces in the Tree w/ Craig Bachmann

Video Caption File/Transcript by Arborist Industry Experts Nick Bonner and Craig Bachmann.

Hi, I'm Nick Bonner and we're here with Craig Bachmann at TCI Expo 2019. This is the not-so-micro rigging lab. It's a little bit bigger than we've had, but you're a veteran on the rigging lab, right?

Yeah, before. You know exactly what you're doing.

Well, I enjoy doing it at least.

Awesome. So we've seen you talk about rigging here. We're going to talk about climbing, we're going to talk about leverage on branches, branch unions, and how force kind of translates depending on which system you've chosen to use.

Yep, absolutely, absolutely.

All right, well, let's do it.

Awesome. Well, thank you very much. Thank you to TreeStuff, and it's awesome to be here at TCI Expo 2019. This is such a great tool to illustrate rigging and climbing concepts, and it's hard to see them sometimes in the tree when the guy's 60 feet up and he's got a microphone and trying to explain this or that. So we're going to try to do it in a small scale today.

As Nick talked about, we're going to talk about loads and we're going to talk about torque. Torque is the idea of bending—it's a load at a distance. Where that comes into play in climbing is our tie-in points, and breaking tie-in points is a consistent source of accidents and fatalities in our industry. So we're going to talk about stationary rope and moving rope. Most importantly, we're going to talk about angles. We're going to talk about angle of attachment, we're going to talk about rope angles, and ways that we can reduce force in the tree.

So let's look at our little scenario we have here. Imagine I'm a climber doing a tree preservation job. I'm pruning and I've got to come all the way out on this limb just to make some reduction cuts or take some dead wood off—something that requires a pretty good-sized limb walk. In our tree, I've got this tie-in point up here.

When we think about loading in the tree, we might use a stationary rope system, we might use a moving rope system, and there's some basic mechanical advantages or disadvantages that come up between those systems. On a moving rope system—I've got a little example here, it's a black rope, it's hard to see—because we have two parts of line supporting our weight, our load is divided, but at the end it is a one-to-one load. Our tie-in point to our body weight is a single load. For me, I weigh about 200 pounds, so I'm putting about 200 pounds of load on our tie-in point. But the question is, what is it doing to bend this? What is it doing to bend that?

So when I need to be out here to make a reduction cut, to go get some deadwood—maybe it's over the client's roof, maybe it's over the neighbor's property—I want to be tied in at the most advantageous point, which is obviously up here. Why wouldn't you tie in there? But what happens is, when I'm tied in here, although I'm only one-to-one loading my system, all of my load is at an angle, almost 90 degrees to that limb. So this angle is creating a lot of torque here. The load at the tie-in point is one thing, but what are we doing at that attachment?

So in our demo tree—this is just a 4x4 post—but imagine up in the tree, you're tied in at 60, 70, 80, a hundred feet, and you're tied into a limb that's six or eight inches in diameter at the attachment. Reducing load, reducing bending moment or torque on this limb—super important. The fact is, we need to find a safe way to get out here that reduces that force.

So let's look at a concept that might be effective. We had talked about stationary—excuse me, moving rope—that makes a lot of sense, that's one-to-one loading. So we talked about using moving rope systems, and that reduces load at the tie-in point. But what about in a stationary rope system? If I were to set up a stationary rope, I might shoot a line from the base, go up over a tie-in point, and come on out here. So what have I done now? Let's imagine we don't have a lot of friction in this system. Potentially, I'm loading this—oh, this is about a 40-degree angle—so I'm loading this at something like 1.8 times my body weight. So if I weigh 200 pounds, 0.8 times 200 is 160, so I'm putting potentially 360 pounds of load on this tie-in point, which is going to translate into potentially 1,500 or 2,000 pounds of torque at the attachment.

So the question is, what can we do to reduce that? One way that we reduce force and load is by opening the angle. So check this out—I'm just going to tie this off so this rope stays in the right place for us. Imagine this is our climbing location, this is where our limb walk is over here. If this is my basal anchor configuration, I am multiplying forces, I'm creating a mechanical advantage on that tie-in point. But what if I opened that angle farther? What if I redirected my line here, or what if it was redirected back here? As I open that angle, the vector—the way the load is applied—begins to move. Our vector force divides the angle. When the legs of the rope are here and we're dividing it, it's pulling outward on the tree. If I can open that angle, that vector moves in closer to the stem of the tree, it's more in line with the limb, and I'm reducing force at this attachment point.

Now realize, we have to be mindful of defects, cavities, potential structural issues, but anything I can do to bring that force vector more in line with the limb that I'm tied into helps protect that attachment. And I'm a big believer that you have to have multiple tools in your climbing toolkit.

So this is an example of using a basally anchored stationary rope, but you could set this up with a moving rope too, with a hybrid system. And if that's not something you're familiar with, let me do a quick demo.

So if I could shoot my line in the tree and manipulate it, pull it up into place, I could attach to it a pulley, some sort of a friction management device, tie this to the end of my stationary rope system.

I'm going to tie a bowline with the Yosemite finish, and when I hoist that up in the tree, all of a sudden now I've created a floating tie-in point for my moving rope system. And that enables me—as I personally like doing limb walks off of a moving rope—that enables me to use a basally anchored system where I have opened that angle. Pull that a little tighter. I've opened the angle, and I still have the advantages of moving rope to perform my limb walk.

So I'm utilizing a variety of different tools, and again, this is a really simple demonstration designed to illustrate some of these concepts: opening the angle to reduce force, moving the vector more in line with the limb so that we load it in compression rather than creating so much torque or bending moment. These tools—as I hope you can—keep those in your head when you're climbing, when you're setting up systems to reduce force in the tree, make your climbing experience better and safer.

So thank you for the opportunity, and I look forward to hearing from you later.