Rope Wrench Feedback?

weight or strength are constants in the equation. THe climbers stength is X. the climbers weight is Y. THey dont make a difference. Mechanical advantage basically trades force for distance or visa versa. Think in a 2;1 the climber is both climbing one side of the rope and pulling himself up with the other side of the rope so his force is distributed across the two sides of rope but the trade off is the distance he has to travel. A groundsman trying to pull someone up the tree would either end up climbing up the rope himself if he were lighter than the climber or if he were heavier it would be a huge feat of strength to pull the climber into the tree.

In a Rads, The climber sets up a 2;1 on oneside of the rope and climbs the tail. He is climbing one leg and pulling up on himself with a 2;1 on the other side while he is climbing the other leg. = 3;1.

In a 100% effecient system his weak arms will only pull 1/3 of his fat butt at a time but he will also pull 3 times more rope through his hands. The climber is pulling himself and climbing simultaneously.
 
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Just wanted to shout out to Kevin for the RW idea yet again! Been climbing in Central Park in NYC, and I'm loving SRT and the RW. Most of the climbs are just straight up, avg 40', get a few limbs/hangers, come down and move on. The RW and SRT is awesome in this application. No time wasted isolating a line, etc.

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I have just such a job this week, white and red oaks, up to about 70 feet in 5 trees, remove a few dead limbs and hangers, then down.

primo for the wrench :) but....Adrian, in a big tree with a huge canopy and a lot of up and down, do you still find DdRT and a hitchclimber/pulleySaver rig better for that? I find, in some trees, still hard to beat that set-up too ;)
 
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...Still not an increase in mechanical advantage. A decrease in the amount of weight that's being moved while the pull is happening, maybe. You can't simply add a "1" to the ratio just because you are in the system. How about adding 1.5... or 2? What if a climber is really heavy but has really weak arms? What if a climber is super light but has super strong arms? What if I jump really high for each pull? What if I'm rescuing my friend and we're both hanging in my system but he's unconscious and I'm the only one doing the pulling? What if I rig a jet pack to the log I'm lifting so it moves toward the fixed pulley during the lift? Have I now changed the MA somehow? The jet pack log takes less input to move, but the MA ratio of the system stays the same.

I am not trying to come across as confrontational....

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Succeeding without even trying. :)

This is some very basic and tree relevant information that you really need to figure out.

Dave
 
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I have just such a job this week, white and red oaks, up to about 70 feet in 5 trees, remove a few dead limbs and hangers, then down.

primo for the wrench :) but....Adrian, in a big tree with a huge canopy and a lot of up and down, do you still find DdRT and a hitchclimber/pulleySaver rig better for that? I find, in some trees, still hard to beat that set-up too ;)

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Not really, once you get the SRT mind set, its hard to go back to DdRT for anything.
 
A redirected 2:1 MA takes 2 feet of pull and 2 feet of rope to get 1 foot of travel (I measured). Take out the redirect and you have a 2:1 MA that also takes 2 feet of pull for 1 foot of travel, but only 1 foot of rope is needed. This is because the extra foot is not needed to make it to the redirect. However, in either case the (theoretical) MA does not change.

I understand the climber's loop system, and I do not believe that what occurs in the loop system applies beyond it to block and tackle rigging, or RADS, etc.

A RADS system uses the same amount of rope per unit of travel regardless who is doing the pulling; climber or ground person.

Who has a link to Peter Donzelli's article from Arborist News that's in the ISA Compendium series? I loaned mine out. As I recall, it briefly described the climber's loop system.

Where is Treespyder? Where is Brion Toss? Give me a formula. I want science!

I'm making a video tomorrow with my throwline and tape measure. The RADS (redirected 2:1 MA) takes 2 feet of rope and 2 feet of pull to advance 1 foot. Pull 2, get 1.
 
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A redirected 2:1 MA takes 2 feet of pull and 2 feet of rope to get 1 foot of travel (I measured). Take out the redirect and you have a 2:1 MA that also takes 2 feet of pull for 1 foot of travel, but only 1 foot of rope is needed. This is because the extra foot is not needed to make it to the redirect. However, in either case the (theoretical) MA does not change.

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You answered you own question here. Two feet down one foot up equals three. climber pulling its 3:1.
For the ground person pulling, two foot pulls the climber goes up one foot. so its a 2:1

Measure the rope in relation to the person doing the pulling not in relation to the ground.

In ddrt the climber pulls down one foot and goes up one foot. If you mark the rope and measure the distance of the climber to the mark on the rope there is now 2 feet. 2;1 system. In a Rads the climber pulls down 2 feet of rope and goes up one foot. There are now three feet of rope between the climber and the mark. 3:1
 
Look at Dave's photo, and assume that the Uni sheave and Ascension sheave are 1 foot apart. That gives 2 feet of rope between the sheaves. Reach up and grab the rope as it exits the Ascension sheave. Pull until the sheaves contact one another. You have just pulled 2 feet of rope and traveled 1 foot. You have taken the 2 feet between the sheaves and pulled it through. That 2 feet of rope is now between your hand and the Ascension sheave. I don't see where you get 3 feet? In the case of RADS, how can that measurement be any different based on who's pulling?
 
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... how can that measurement be any different based on who's pulling?

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How is it possible to have advanced so far in the tree industry, as a climber, and not grasped this concept? I would suggest that you stop pouring over charts and graphs and looking to science for your answers. You already know this, you're just not recognizing it.
Take one fixed overhead pulley. Run a rope through it. If a 150lb man is tied to one end and another 150lb. man pulls hard enough to lift the other, that line will be loaded with 150lb per leg.
Now if the 150lb man tied to one leg and grabs onto the other and lifts himself, the line will be loaded with 75lb on each leg. A dramatic change in the situation produced by who is doing the pulling.
The basic physics here are not negated by the addition of more pulleys so they cannot be discounted as not existing.
The efficiency of the system, as far as friction losses go, also does not negate the fact that it is a system. You can have a high efficiency (climber with a super efficient pulley) or a low efficiency (climber with rope thrown over rough branch) both are 2:1 systems when the climber is doing the pulling. One just transfers a higher rate of mechanical advantage.
Go out and try it, don't just try to analyze it on paper or pictures. The differences are plainly obvious and easily felt.
Dave
 
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Perhaps this line of discussion would be best continued in its own thread. Just a thought. ...

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You're absolutely right, Shawn. This post was moved to its own thread: RADS Theoretical Ratio

My apologies to TreeStuff and the others for my participation in the protracted derail. Now back to your regularly scheduled program ...
 
Perhaps this line of discussion would be best continued in its own thread. Just a thought.

As per the topic of this thread, "Rope Wrench Feedback", frickin love it!!! Have been on my homemade pulleysaver for about 2 months, and only used the WR to access my TIP during that time, and I cant believe how much Ive missed it. Worked a fantastic wide spreading oak yesterday for fun, and just absolutely loved it. The ease with which one can redirect is enough selling point on its own, but throw in the fantastic handling characteristics, and Im sold!

Ive been using a quick connect pin in the upper holes, with a bushing installed with that midline, adjustable bushing all the way in the "open" position. Im using a 6" petzl dogbone going to a CT oval in the top hole of my hitchclimber for the WR attachment. Climbing on 10mm ocean, with a 6 wrap Michoacan. Best setup Ive used, EVER. Mad props to Sir Bingham for this gift of climbing ecstacy!
 
Ok, i've finally got it. Had to change my whole world to get there but its there. Vortex, hitchclimber, 8mm OP, Double ascender with teather to advance the wrench. 1st time up, the friction was too tight on the wrench. It was like pulling a second person up with me by hand. Kicked my a$$. Loosened the pin and opened it wide up. Second time up is a charm. The only thing I cant get used to is moving past a limb or through a crotch when you're not near the tree and all the hardware is basically underneath the wood and cant be advanced. Super awkward for me and it just hasn't clicked.
 
Arbor care,
This is a one of the things you just have to get used to but no big deal. Get your wrench as high to the crotch as possible and weight your Pantin and free climb until you are safe and lanyard in. You just free climb a little more and it’s all good.
 
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