Friction hitch on double rope

[Tree Machine]

Before we go any further, does this Jive with everybody? I mean, if I am full of crap, please call me out. If you're freaked out about this talk of using metal pieces in treecare, or you're just very intimidated by it, by all means, step up and tell us why. We can use this as group counseling.

I think, though, as you understand the dynamic of friction generation and heat transfer you'll get very clear on what the device is doing for you.




Questions?

 

[squisher]

Keep going very intriguing and interesting. One of the best threads going right now.

 

[OTG BOSTON]

Before we go any further, does this Jive with everybody? I mean, if I am full of crap, please call me out. If you're freaked out about this talk of using metal pieces in treecare, or you're just very intimidated by it, by all means, step up and tell us why. We can use this as group counseling.

I think, though, as you understand the dynamic of friction generation and heat transfer you'll get very clear on what the device is doing for you.




Questions?

TMI---not that you all haven't made valid points.

Bob's original question was if anybody was using a friction hitch on a double rope. My answer, NO, however I did see an oldtimer use a traditional two wrap prussic(half inch line) on a doubled half in. line.

Then I think the question changed to are there any other devices that can be used? I don't know of any.

Bob, correct me if I'm wrong but you used my double ascender at the climb event we did, and all you want to know is if there is a device that can go up like the ascender AND lower you safely to the ground, without changing hardware.

Having said all this: I am easily confused so please continue

 

[Tree Machine]

Bob's original question was if anybody was using a friction hitch on a double rope.

First, he meant to say 'doubled'. Bob went on to ask 'is there a friction hitch that will go down a stationary, doubled line' and that he has ascended on dual, and was wondering if, rather than pull the tail up and fashion a traditional 2:1 DdRT, could he just go onto the dual line and descend it. That was the question. He was just asking if it could be done on a friction hitch.


"No" was the quick answer to that and our talks of heat generation and friction can help better understand the 'why?'. Excess wear and tear, and poor overall performance.

I did see an oldtimer use a traditional two wrap prussic(half inch line) on a doubled half in. line.

And how fluidly was he moving about the crown with his chainsaw, pole pruner, two silkys and a rack of slings and biners? If he can't move through the crown with tools and get his job done, the technique is useless in commercial treecare. 100% total control of the friction using minimum effort is not achievable with a two-wrap prussik.

Bob, correct me if I'm wrong but you used my double ascender at the climb event we did, and all you want to know is if there is a device that can go up like the ascender AND lower you safely to the ground, without changing hardware.

You're talking about an all-in-one unit. That's called the unicender. If there were a miracle device out there that was rock-solid in it's ascent & descent capabilities, a one-piece, do-it-all device, I think you would have heard about it. It's not out there, but maybe some day it will be.

For now, we have awesome ascenders that ascend like there was no tomorrow. It is what they were designed and intended to do. There are lots of models to choose from, even titanium. It's very efficient which is why we use ascenders in the first place. 100% control of ascent. We have ascending covered.

Descending on dual, now we get back to the question and keep this train on track.

 

[rmihalek]

OTG, I vaguely recall your climbing rig but not accurately enough to expound on its virtues. One thing I was saying to Moss when discussing the next Boston Rec climb was that I wanted to try your system out some more. I seem to recall that I could just climb the rope hand-over-hand and if some one was holding the running end, the hitch would self feed and I could zoom right up the rope.

TM, I have no problem using a metal device for self belay when descending. Does anyone know if such a device is made that can be used on a doubled rope and has a "let-go-and-stop" safety feature similar to a Blake's Hitch on DdRT?

I guess what I'll eventually end up doing is ascending with SRT and then switch to DdRT for moving about the tree and a self-belay descent.

 

[TheTreeSpyder]

i think in general; hardware you can descend on you can't use as safety to ascend on; because you can place pressure below the device to lift self or device fights you. grabbing higher than device; rope won't pull through device.

Similarly, holding a line tight below someone, can make it easier to ascend with software (hitch); but impossible with descending hardware (fig. 8, Muenter);as one of the defining characteristics of the 2 strategy types.

More and more examination has all ways brought me back to more respect for each system; in it's own specialty; including our hitches on DdRT; in their correct place/ setting. Especially when i tried to find a similar ascend/ descend hitch/hardware to work as well in SRT/DRT/DbRT 1:1 strategies as cleanly as our handed down DdRT(besides it's particular flavour of 'faults'/ tradeoffs).

Friction is how it these machines all work to support; but as a double edged sword of it's own yin/yang tradeoffs; also what we fight in these devices.

 

[jefflovstrom]

I cannot believe this is still going on.
Jeff Lovstrom

 

[squisher]

C'mon man it was just started on the sixth that's not that long. Isn't this what it's all about sharing thoughts, theorys, and experiences with different gear and techniques. I mean what else are climbers going to talk about.

 

[Tree Machine]

Jeff, we're just getting warmed up.

Of the hundreds of threads, only a handful are about climbing, I mean, climbing. This is commercial treecare, meaning we get paid for what we do. The forum is called Commercial Tree Care and Climbing. The thread, right here, right now, climbing. This is highly focussed, specific to one little-used rope method and we're about to fully describe it as it applies to professional tree climbing. This is as climbing as it gets.

Coming down a dual line has been lightly gone over at Arboristsite for just over 4 years. This is the furthest we've gotten yet.

 

[OTG BOSTON]

OTG, I vaguely recall your climbing rig but not accurately enough to expound on its virtues. One thing I was saying to Moss when discussing the next Boston Rec climb was that I wanted to try your system out some more. I seem to recall that I could just climb the rope hand-over-hand and if some one was holding the running end, the hitch would self feed and I could zoom right up the rope.

TM, I have no problem using a metal device for self belay when descending. Does anyone know if such a device is made that can be used on a doubled rope and has a "let-go-and-stop" safety feature similar to a Blake's Hitch on DdRT?

I guess what I'll eventually end up doing is ascending with SRT and then switch to DdRT for moving about the tree and a self-belay descent.

That is a schwabish prussic with a micro pulley---very simple rig. I thought you were referring to the doubled ascender I have for footlocking.

Using both is probably the way to go!!!!!!!!

 

[Tree Machine]

Please describe with a picture if possible. Arboristsite visitors just love pictures.


A picture of friction is a toughie. Friction is a force, like magnetism, gravity, elesticity. You can't see the force itself, which makes it a little harder to understand. But you can experience the effects of the force, and you generate heat as a by-product.



Controlling friction, therefore, is controlling heat, meaning the less friction overall you apply to the hitch or device, the less wear and tear on all parts of the system. Highly accurate application of either lower-pressure, distributed friction or higher pressure, concentrated friction. In the dual-line setup we are talking about with the two lines, each line need only pick up 50% of the friction duty. The pressure really isn't all that great. The friction, by design, is being spread over a more distributed area. How you climb and how heavy you are will dictate how much friction and wear you are creating.


The design of the device may keep ropes seperated (maybe by just a couple millimeters), OR the design of the device (or your unique use of it) may cross the rope over itself creating a 2-part friction system in one.

The simplest sub-family in the world of mechanical pieces uses simply rope-on-metal.

 

[SRT-Tech]

We are pretty much in 100% agreement on this subject. I would like to point out that all of the friction at one point does generate quite a bit of heat too. I've heard stories of long, fast descents......that when brought to a stop..... the device has melted the climbing rope...resulting in a fall.

I've never known someone this has happened to but it does sound plausible, or it could be an urban legend.

Its called "rope lubricated rappel causing uncontrolled descent", common with rappel racks on LONG DROP (200 - 3000 foot rappells on big walls). basically the rappel rack (on long drops) CANNOT dissipate the heat (caused by friction) fast enough, which causes the rope to get glazed, then you descend faster, then the rope and rappel rack heats up even hotter melting the rope, which in turn further lubricates the rack with hot melted nylon, until you simply cannot control the rappel anymore and you slide at high speeds into the ground. Often time the rappel rack and the base of the big wall/cliff will be covered in orange sized globs of melted rope.

when you suddenly stop a rappel, the heat buildup in the device is CONCENTRATED on one tiny spot of the rope (around 2 - 5 mm), thats why in some cases it will suddenly melt thru (if the heat on the rappel device is hot enough). That is why it is better to COMPLETE your rappel to ground, then keep pulling rope thru your device to prevent hotspotting.

Now if you think this ("rope lubricated rappel causing uncontrolled descent") is possible in in tree climbing, think again.....we are NOT descending LONG DISTANCES or descending LONG ENOUGH to create excessive heat!!!!! . We are descending maybe at the most 200 feet, if that. There WILL be some heat from friction, but not enought to cause the treeclimber to enter that "rope lubricated hiway of death".

ON ROPE goes into more detail about this, but we as treeclimbers really dont need to worry about it.

 

[Tree Machine]

Thanks for that, SRT Tech. Another note to add to the friction / heating scenario is that the heavier the climber, the more the friction (as well as tension on the rope). I am in agreement with you that "rope lubricated rappel causing uncontrolled descent" is very, very unlikely in tree climbing. Possibly in recreational where the highest trees are often the goal or inexperienced yahoo demons showing off, rather than paying attention to their safety.

I attended a presentation last year at our monthly caving meeting. One of the members had had been out to a national park and rappelled down the face of a monlithic boulder called Half Dome. It was shaped like half a boulder, but had the size of a mountain. It was a very, very long drop, a good chunk of the day just coming down a rope. The presenter said he could sense the heat building up to dangerous levels and used his water bottle, drenching the rack to pull off more heat. It's probably a good thing he did. Those oblivious to the heat generation will be the ones lying next to the gobs of melted plastic.

Over the last 14 years I have used a lot of different devices and all the friction hitches ever covered here at Arboristsite. Close attention is paid to heat, friction, wear on the device/hitch/tress cord and the wear on the rope, as well as how tight a bend on the rope as it passes over a device at the point of friction knowing that the tighter the bend, the more stresses on the fibers and weakening of the rope at that point.

A parallel doubled rope takes 1/2 the friction per line. Additionally, if the friction center utilized both rope-on-metal friction as well as rope-on-rope friction, as well as control friction from your hand, the heat is distributed around and shared to a good degree. Any heat generated into the rope itself is left behind (above), sparing the device from the full amount of heat buildup. Personally, I like a setup that distributes the heat around in this way, rope-on-rope and rope-on-metal. Most devices, however, take the entirety of the friction (pure rope-on-metal). Some will be absorbed by the rope, but rope doesn't absorb heat well (unless it's wet).

Thanks again, SRT. I would encourage everyone, however, to be aware and be in understanding of what is going on. A simple, non-scientific way to measure the heat generated after a long descent or a really fast descent is to touch the device. If you want even more accurate non-scientific measurement, purse your lips right up to it without actually touching. If you do this 50 or a hundred times you get a very good idea of the level of heat you're generating. Like SRT says,

we as tree cimbers really don't need to worry about it.

As far as the use of devices on a doubled parallel line, it's more important to apply the rope within the device correctly, to be certain how much hand-control it takes to slow or stop, and where are your positions for soft lock / hard lock. Each device is unique, even within the same class of devices. Each class works on the same principal, but it is the finer nuances of it's performance that will determine precisely how it is used.

 

[Tree Machine]

The next very important point (before we actually go into specific doubled rope descent devices) is the difference between two similar terms.

The terms are Rappel (or abseil) and self-belay. Anyone wanna take a stab at how these are different?