Basic Mechanical Advantage for Arborists

Video Caption File/Transcript by Arborist Industry Expert Nick Bonner.

[Music] Hi, I'm Nick Bonner for TreeStuff.com, and today we're going to cover the basics of mechanical advantage as it applies to arborists or tree care work. There's definitely a ton of information available—we're not going to cover it all, but we are going to try and cover some of the easy things that you can do and some of the more complex systems.

For the purpose of our example today, I've got a pulley above us. It's a relatively low-friction Rock Exotica pulley. I've got a rock that is—it's heavy. I'm not sure exactly how much it weighs, but you can see, you know, I'm not a very big guy, and I'm struggling to try and lift this here. The rope that we're using today is fairly small diameter, but I chose it because it has very little stretch. It has a Dyneema core with a polyester jacket, so it should help us show what we're trying to show today pretty well.

So you can see that I struggle to lift the rope by itself. So what I'm going to do is I'm going to go ahead and unanchor it from our Portawrap here, and I'm going to show you one of the simplest forms of mechanical advantage, which is often called an old-school come-along. So I'll come here as about as high as I can reach on this line, and I'm going to tie an alpine butterfly very simply in the end of the rope like that. I'm going to keep the Portawrap over here. Instead of a pulley—this would be more efficient with a pulley—but we'll keep the Portawrap for the purposes of this initial demonstration.

So here, I'm going to take the tail of the rope, and I'm going to pull it through this knot, and I'm going to form a really basic three-to-one system. So you see here, I can start taking it up, and I'm making more progress with the rock now than I was before. Still, it's not easy, and you notice when I let go of it, the rock's going to just come straight down to the ground. There's no progress capture, and I also don't have any ability to reset this system. Once this knot comes to here, I've exhausted all of the pulling that I can do, and because I'm using the redirected tail, it would be difficult for me to lock it off and try to move this at all, right?

So, this is a good system when you're trying to pull a tree over that maybe takes a little bit extra force. You know, you've got a couple of guys, you can really, you know, multiply the amount of force that they're able to put in without a bunch of tools. If you're going to be doing a really heavy lift or something super critical, this isn't the type of system that I would recommend, but it is the same basic technique.

So let me just undo this alpine butterfly here, and what we'll do is we'll show a different version of this.

And I'm going to take a prusik, and I'm just going to put a pretty standard French prusik or English prusik on here. It's a three-wrap, so you end up with like six coils here, and I'll just go ahead, set that, and then I'm going to take a very simple pulley—this is nothing fancy, it's a simple swinging side plate pulley. This one happens to be made by CT. Pretty much any similar pulley that's rated appropriately is going to do the job.

So, same concept again, where I'm doing that. In this instance, I'm going to take the rope off of the Portawrap and put a pulley in at this side as well, and I'll clip that straight to the top of the Portawrap. So now, again, this is the same three-to-one system, but I've got a lot better efficiency here because of the pulleys. But still, no way to stop it or put any type of progress capture on or anything like that, because I'm still using the leg of the rope as a redirected way to create the mechanical advantage. I could obviously lock this off on the Portawrap, but I still don't have any way to reset it using this technique.

So what we'll do now is we'll go ahead and use an external mechanical advantage setup. That could be something as simple as a piece of rope with these types of pulleys to build a mechanical advantage setup, or you can use something that's pre-made like this. This is a really nice setup—the Rock Exotica Aztek setup. This features Sterling rope and a really nice set of fours pulleys. Again, you don't need to have something like this, but it is really helpful, and we'll show you a couple of the reasons why here today.

So, go ahead and take some of the slack out of this.

All right, so here we go, and you can see I'm able to lift the log with relative ease. However, it's a lot of rope being pulled out, and now again, I've gone ahead and exhausted my pull, so I need a way to reset it and ideally to have some progress capture. So I'm going to take the tail of the rope, and instead of just leaving it hanging, I'll insert it on the Portawrap like normal. So now what I'll do is I'll install this orange control prusik up here on the top of the pulley. This is really nicely built in to this Rock Exotica Aztek setup, but this could be done, like I said, with a piece of scrap rope, and this could just be an extra normal-sized prusik that you attach to this carabiner and then attach to the right leg of your mechanical advantage setup.

So you can see here, as I'm applying pressure, it's holding it here with this prusik, allowing me to really focus on putting the force in and getting it set up. Now again, I've exhausted the pulling distance, and I want to reset this, I want to move it, so I'm going to come in here and I'm going to break it with the Portawrap, lock that Portawrap off with two half hitches around the pins. I'm able to disengage this prusik, and now I can move this up as far as I'm able to reach and re-engage my pulling.

So this is just one example of how you can use a set of fours like this, or a fiddle block system, or any type of mechanical advantage setup with a prusik and a Portawrap to create a simple system where one person can raise, stop, control, and lower a load that they might not otherwise be able to. All these different types of tools and techniques are going to be interchangeable with various types of pulleys, whether you've got fancy ones that split apart and have magnets in them, or just simple becket pulleys like you see here from DMM with the Pinto.

So, hope that you were able to learn something today. If you find yourself in your backyard and you need to lift the rock, or maybe you're on the job site and you need to lift a log, these techniques should come in handy. Thanks for watching.