imagineero
Addicted to ArboristSite
Just thought I'd pass along a handy tip a fellow climber gave me recently. I've used it quite a bit and it saved my bacon on one job.
A few basics out of the way first for the lurking new guys out there so you don't hurt yourselves (I know you're out there).
Here's a basic lowering setup, and not a very good one. We've got a single pulley rigged as a high point, a porty or friction drum or whatever on the ground, and a 1000lb branch being cut. We're going to forget lots of things like how the branch will swing, whether the line will be pretensioned, friction and losses, dynamic loading etc. It is worth noting however, that if there is a dynamic load (the branch drops because you can't pretension the line) then you can see a load of up to 5 x the weight of the piece, especially barrels which have no foliage to slow them down which means up to 10 x the weight of the piece at the pulley. Yeah that's right, a 2000lbs shock load from a 200lb branch.
In our simple example, if we put 1000lbs load on the end of the line, the friction device will also see 1000lbs, and the pulley will see double that - 2000lbs. The worst part about this setup is the fact that the force loading is pulling the branch downwards, increasing the chance of breaking it.
Moving right along.... This next scenario is nothing new to most of you and is a pretty standard rigging setup. 2 pulleys, set at approximately equal heights in the tree will share the load equally between them. Things are much better from a loading perspective here. Not only are the pulleys sharing the load (taking half the force of the first scenarios), but the force is now along the axis of the branches, loading them in compression. A lot stronger. It also gives you 2 high points to use. You can pull the tail through and switch ends of the rope to work both sides of the tree. This is a setup most of us probably use for basic work. I use this setup most of the time, with a 3rd floating pulley that I carry with me and rig to get a local lower off point to where I am since trees are 3D and there isn't always room to swing a branch all the way back to that high point.
So here's the tip.
Use a 2:1 in the tree. It's just like using a double fall setup on a crane. I'd done it a couple times in past, mostly to create a fictitious lower point, but had never really used it much because of the time to set it up. The setup time was because I was setting the 2 points far apart, out of necessity, but there's no reason not to use it locally for the 2:1 advantage. In truth you lose the 2:1 the further apart the 2 points are. There is some advantage to leaving the pulley far out, and having the tie off close in - the piece will float away from you when you cut it. But mostly, you'll want to rig a floating pulley directly above your desired lower off, down to the branch, then back straight up to tie off next to the pulley. You'll get the most mechanical advantage that way.
Instead of tying off to your piece, put a pulley on it and thread the rope back through then tie off the tail. Now, you've halved the force on the pulleys, which is nice... but you've also halved the load the rope is seeing. The big thing though, is that you've also doubled the lifting/holding power of your friction drum.
This isn't just a big tree thing - though it is handy on big trees for sure. It really speeds up lifts even though you need to lift twice as much rope for the same amount of lift at the branch - the effort required on the ground is a lot less which really speeds up the work. It also gives you a lot more finesse on a porty. You've lost a lot of the feel of the rope by the time you've got 3 or 4 wraps on a porty. With a 2:1 in the tree that might be only 1 or 2 wraps which gives a lot more control on the run.
"But look at all those pulleys! And now I need an even longer lowering rope! Don't you know how expensive big pulleys and 3/4" lowering ropes are?"
Good news is that you don't need big ropes and big pulleys any more. Using a 2:1 in the tree brings most removals into the realms of 1/2" rope and pulleys which are cheap and plentiful. If you use a ratchetting pulley and the tree isn't that big then you may not even need a porty any more. You can lift and lower by hand which really is fast! Even a little lift is a good thing.
"But I don't have a friction drum!"
Ok, so here's one for you....
I was using mechanical advantage a lot last year before I got my friction drum which is awesome and has replaced my family. Mechanical advantage is slow and painful, but it's cheap and effective and if you only have one or two branches to remove then go right ahead. Besides, if you don't own a friction drum your phone isn't ringing off the hook so you've got nothing but time.
In this example, we've got the basic 2 pulley high point setup, and a floating pulley out there over the house because otherwise the branch would be swinging way back in. It's a happy house as you can see from the 2 windows, so dont make the people unhappy by damaging the slate roof. Rope goes through the floating pulley, down through a pulley on the branch, then back up for the tie off. Due to the angle on the rope going through the floating pulley it sees very little load so you can haul a big ass piece off it.
Put a pulley on the base of the tree to bring the rope parallel to the ground. Now 2 or 3 guys can meaninfully put pull on the rope by hand. If the rope was going straight up, only 1 guy could really pull. Put your porty on another tree as shown. Now put a friction hitch around your lowering rope. Attach your 2:1/5:1 or whatever you've got to it.
You can preload the branch with this, then wrap the lowering rope on the pulley and take the friction hitch off for a straight lower. Or if you've got a bunch of ligting to do, then lift until you run out of rope, secure the lower rope on your porty, slide the hitch back out again, and repeat as many times as needed. Which may be a lot on a 5:1! But with a 5:1 on the ground, and a 2:1 in the tree.... a single groundie can realistically lift 500lbs with some effort.
"But I have a big ass crane, I laugh at guys who have friction drums"
Screw you.
Shaun
A few basics out of the way first for the lurking new guys out there so you don't hurt yourselves (I know you're out there).
Here's a basic lowering setup, and not a very good one. We've got a single pulley rigged as a high point, a porty or friction drum or whatever on the ground, and a 1000lb branch being cut. We're going to forget lots of things like how the branch will swing, whether the line will be pretensioned, friction and losses, dynamic loading etc. It is worth noting however, that if there is a dynamic load (the branch drops because you can't pretension the line) then you can see a load of up to 5 x the weight of the piece, especially barrels which have no foliage to slow them down which means up to 10 x the weight of the piece at the pulley. Yeah that's right, a 2000lbs shock load from a 200lb branch.
In our simple example, if we put 1000lbs load on the end of the line, the friction device will also see 1000lbs, and the pulley will see double that - 2000lbs. The worst part about this setup is the fact that the force loading is pulling the branch downwards, increasing the chance of breaking it.
Moving right along.... This next scenario is nothing new to most of you and is a pretty standard rigging setup. 2 pulleys, set at approximately equal heights in the tree will share the load equally between them. Things are much better from a loading perspective here. Not only are the pulleys sharing the load (taking half the force of the first scenarios), but the force is now along the axis of the branches, loading them in compression. A lot stronger. It also gives you 2 high points to use. You can pull the tail through and switch ends of the rope to work both sides of the tree. This is a setup most of us probably use for basic work. I use this setup most of the time, with a 3rd floating pulley that I carry with me and rig to get a local lower off point to where I am since trees are 3D and there isn't always room to swing a branch all the way back to that high point.
So here's the tip.
Use a 2:1 in the tree. It's just like using a double fall setup on a crane. I'd done it a couple times in past, mostly to create a fictitious lower point, but had never really used it much because of the time to set it up. The setup time was because I was setting the 2 points far apart, out of necessity, but there's no reason not to use it locally for the 2:1 advantage. In truth you lose the 2:1 the further apart the 2 points are. There is some advantage to leaving the pulley far out, and having the tie off close in - the piece will float away from you when you cut it. But mostly, you'll want to rig a floating pulley directly above your desired lower off, down to the branch, then back straight up to tie off next to the pulley. You'll get the most mechanical advantage that way.
Instead of tying off to your piece, put a pulley on it and thread the rope back through then tie off the tail. Now, you've halved the force on the pulleys, which is nice... but you've also halved the load the rope is seeing. The big thing though, is that you've also doubled the lifting/holding power of your friction drum.
This isn't just a big tree thing - though it is handy on big trees for sure. It really speeds up lifts even though you need to lift twice as much rope for the same amount of lift at the branch - the effort required on the ground is a lot less which really speeds up the work. It also gives you a lot more finesse on a porty. You've lost a lot of the feel of the rope by the time you've got 3 or 4 wraps on a porty. With a 2:1 in the tree that might be only 1 or 2 wraps which gives a lot more control on the run.
"But look at all those pulleys! And now I need an even longer lowering rope! Don't you know how expensive big pulleys and 3/4" lowering ropes are?"
Good news is that you don't need big ropes and big pulleys any more. Using a 2:1 in the tree brings most removals into the realms of 1/2" rope and pulleys which are cheap and plentiful. If you use a ratchetting pulley and the tree isn't that big then you may not even need a porty any more. You can lift and lower by hand which really is fast! Even a little lift is a good thing.
"But I don't have a friction drum!"
Ok, so here's one for you....
I was using mechanical advantage a lot last year before I got my friction drum which is awesome and has replaced my family. Mechanical advantage is slow and painful, but it's cheap and effective and if you only have one or two branches to remove then go right ahead. Besides, if you don't own a friction drum your phone isn't ringing off the hook so you've got nothing but time.
In this example, we've got the basic 2 pulley high point setup, and a floating pulley out there over the house because otherwise the branch would be swinging way back in. It's a happy house as you can see from the 2 windows, so dont make the people unhappy by damaging the slate roof. Rope goes through the floating pulley, down through a pulley on the branch, then back up for the tie off. Due to the angle on the rope going through the floating pulley it sees very little load so you can haul a big ass piece off it.
Put a pulley on the base of the tree to bring the rope parallel to the ground. Now 2 or 3 guys can meaninfully put pull on the rope by hand. If the rope was going straight up, only 1 guy could really pull. Put your porty on another tree as shown. Now put a friction hitch around your lowering rope. Attach your 2:1/5:1 or whatever you've got to it.
You can preload the branch with this, then wrap the lowering rope on the pulley and take the friction hitch off for a straight lower. Or if you've got a bunch of ligting to do, then lift until you run out of rope, secure the lower rope on your porty, slide the hitch back out again, and repeat as many times as needed. Which may be a lot on a 5:1! But with a 5:1 on the ground, and a 2:1 in the tree.... a single groundie can realistically lift 500lbs with some effort.
"But I have a big ass crane, I laugh at guys who have friction drums"
Screw you.
Shaun
