Leveraging Mechanical Advantage to Pull Over Trees
What is your tree clearing business using to pull over trees? Just a rope and one of your ground workers? Maybe a couple ground workers? What if you need to pull more than they are capable of? Using pulleys to create additional mechanical advantage helps add as much pull as possible, and is a great way to get those big flops and drop jobs on the ground! Let's take a look at some easy ways to create a mechanical advantage!
Understanding Mechanical Advantage
First off, mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. That makes sense, right? We are multiplying the amount of force we are putting on the tree we are attempting to pull over. We can achieve this by using pulleys on the rope being pulled, using a geared system like the GRCS or using a piece of machinery like a mini skid steer. All of these are examples of mechanical advantage. Today, let's take a look at using pulleys to create a mechanical advantage!
Creating Advantage with Pulleys
First off, the easiest and most economical of our examples is by attaching pulleys to the rope you are pulling as well as an anchor point. The rope would be attached to the tree you are attempting to pull over and then ran into the pulling area that is at least 1.5 times the height of the tree you are removing. Now, the first pulley can be attached to a solid anchor point with a sling and the rope can be ran through the sheave. Now a prussik can be attached to the rope a distance away from the anchor point. Next, attach the other pulley to the prussik with a carabiner and run the tail of the rope through the sheaves of this pulley. If you are using double sheave pulleys, you can run the tail of the rope back to the anchor point and run it through the next pulley sheave. Then follow up with putting the tail through the next set of sheaves on the pulley attached to the prussik. At this point your tail should be getting pretty short, but this means your mechanical advantage is growing!
A great way to determine how much mechanical advantage you have is by counting the pieces of moving rope between pulleys. With the above-mentioned system, you should have a 4:1 mechanical advantage. So, if one of your tree removal service guys can pull 100 lbs on their own, they should be able to put 400 lbs of pulling force to the tree being pulled over! That's huge if you only have one person helping you!
Maintaining Your Progress
Another really smart thing to add to your pulley setup is a prussik to capture progress. What would happen if you still couldn't get enough pull on the tree to get it to come over and it started going the opposite direction that you planned? Technically, the rope would just pull out of your ground crews' hands at an extremely fast rate and the tree would probably fall. If you added in a progress capture prussik, it would grab the rope any time it started to go in the opposite direction. The prussik can be added on to the rope at the pulley that is attached to the tree. It will be installed on the second leg of rope after it goes through the second pulley sheave. This will allow the rope to pass through the prussik when you pull but as soon as you let go, the hitch will grab the rope. Obviously, you need to make sure that the hitch is guaranteed to hold.
You can create this mechanical advantage system for yourself with an ISC Small Aluminum Double Pulley and one of our Tenex 10mm prussiks!
Be sure to check them out on the Bartlett website and share some of your favorite ways to leverage mechanical advantage for pulling trees in the comments!