CMI Twin Expedition

I did not own a set of dually redundant duals back then. I'm sorry, Tyler did not see me climbing on these. They weren't single-handled, and they weren't dually redundant in the safety features. This is entirely new gear from before, related, but way, way different in performance.

The game has changed a lot.

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What are other advantages of double line other than retrievabilty and bigger purchase area for footlock. I like the retrievability


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Not even retreivability so much, that has nothing to do with the ascent/work climb. That's just repositioning the rope, nice if you have a long line of trees and you're able to traverse the canopies.

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dont think footlocking a single line is very difficult.

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Nor do I. but this is the science behind it;

SRT one rope beneath you, not moving.
TWIN two ropes beneath you, not moving.
DdRT one rope below you, moving downward with every footlock, which is why footlocking DdRT is generally considered a pain in the arse, soiling the true advantages of what footlocking can do for you.

Footlocking to ascend a twin line is unquestionably easier than on a single line..... there is twice as much rope to create foot-on-rope friction. Again, the phsyics don't lie. Physisics. Phizzz. Ugh. As well, the dual ascender, as with a single ascender, adds negligible friction going up. Now, you can move the ascender freely, at will, up or down, and with this, there is no difference between twin and SRT. The difference is that most guys like some rope to grip onto with their non-ascender hand. With 11 mm, in a twin rope configuration, you have ~22 mm of rope to grip. The hand thing and the foot thing I see both as advantages in twin rope ascent, pretty much everything, if you ask me.

Half the stretch in the rope, another little advantage, less bounce.

No tying off (anchoring) to the base of the tree.

Forces distributed 50% to each side of the ascender making the practical working load on each side of the ascender halved.

Guys tend to want to climb on 13 mm SRT, which is fat, heavy rope. Twin welcomes the lighter more amble 11 mm and all the advantages that carries, while still giving big rope(s) to handle below the ascender.

In descent, using a twin line descent device, each side of the rope takes half the wear, half the forces, distributes heat equally and need only provide half the frictional forces, each side taking on half the duties. This translates to half the wear and half the hand-belay pressure when using certain dual-sided friction devices. This is an advantage that must be experienced, light fingertip control pressure, precise, smooth.

Crawlovers, possibly one of the biggest advantages I can see. In DdRT these can wreck your ascent. In twin, you can look forward to limb crawlovers. Really. You can do & go places with a 4 wheel drive vehicle that you can't with a two-wheel drive. This is sort of like that. Twin can do everything SRT can do, and additionally can do the things it does uniquely well.

Just having different options to exercise, being able to drop through crotches into 2:1's/3:1's like you do in SRT, all that stuff you would never, ever consider doing inn DdRT, you can now look at differently. A twin line offers 2X the friction on drop-throughs, making the belay hand friction halved as compared to the same being done SRT.

Being able to use redirects and drop through natural crotches, like in SRT, & great abilities to set safety through slinged redirects.

Really, there is nothing that SRT can do that Twin line can't. Twin doesn't require anchoring one end. Lace your rope up and over, clip in, and go.

I could go on with finer details, maybe another time

Since we are essentially talking about ascent and work positioning with these things, all things considered, the dual should blow the single out of the water because the dual can BE a single, by just using one side. But the dual can go twin, which really opens you up to new options, hopefully enhancing your safety, confidence and abilities.

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... I am very intrigued. I would like to see it in action. ...

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YEAH!!! I am intrigued, too, TM. Been <u>reading</u> 'bout your system for a looong time - truly great work. Seen a vid of you breaking the world record
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for winding throwline. So, we know you can do videos. Is there any chance you could post a vid of your system at work - up, down, around. That'd be waaay coooool! PLEASE, PLEASE, PLEASE!!!
 
I believe he is implying that you simply grab one leg of rope (below the ascender) for friction and thumb open the cam on the corresponding side of the ascender. This allows the other leg of rope to run freely while your rope hand controls speed and friction. I could be very wrong, but that is certaintly how I interpreted his description. I second the need for a video of this technique. I am quite intrigued....
 
What did you say back there, TM, they corner well. I'm waiting to see that in action. They go through crotches?
 
Iterim report...

I've had one for a week now but all I've been doing is excurrent trees so I don't have much to say about working with it yet, but here's what I have so far...

It works better than my taped together Petzls. It's smoother on the rope and the handle is more comfortable. It stows better too since it's less bulky.


This is not an earth shattering development but definitely IS an innovative improvement of the original concept. The SHD has left the realm of prototype and is now a production unit.

We needed this because now maybe more climbers will feel comfortable trying the single handle dual. It's a very efficient way to climb if you can footlock and the redundant safeties pretty much guarantee the ropes cannot escape the cams even if you actuate the triggers and forcefully TRY to get them out.

The cam pins are fat, looks like 3/32" or maybe 1/8" in diameter. It might break after years of wear but any shock load capable of shearing that pin will shear your body a lot worse.

Can the frame fail? I suppose so but see my previous point, you wouldn't survive that kind of force anyway.

Can a twig jam one of the cams open? Yep sure could, just like any other ascender or knot.

Do you HAVE to back it up? Only you can say for yourself. I think on doubled rope this device is about the safest way you can climb. But I also don't like climbing with only a single rope attachment so I'm looking into it. So far, the tether is what I keep looking at when I'm climbing, the ascender feels strong.

Tethers... I bought some All Gear HTLL and the first thing I made with it was a tether for this ascender... so I felt like a real idiot going 70' up a pine on a new ascender with this HTLL tether having never even attached it to a rope before... so I backed it up. Two pines later I was leaving the backup off. At this point I'm undecided about backing it up. It feels super solid.

Joshua, the dual handle has been out for a while now, thing is, it forces you to your wrists outward when you pull down and that's not nice to your connective tissue.
Also about double handles... are you climbing with your arms or your legs? You shouldn't need both arms since all you're doing is supporting your body weight and pulling it in to the rope. If you're hauling a bunch of weight up with your arms you need to learn to use your legs more efficiently.

The SHD bypasses limbs easily compared to other ascenders, it would bypass a crotch about as well.

Also, about the doubled line... think TIP... 1/2 the force on your TIP as you jug upward versus trunk tied SRT. To me, that's the hitch with SRT, I don't like doubling the effective force on an unknown TIP while ascending... especially if I don't HAVE to.
 
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The SHD bypasses limbs easily compared to other ascenders, it would bypass a crotch about as well.



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What's is the feature that allows that kind of action.
 
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Also, about the doubled line... think TIP... 1/2 the force on your TIP as you jug upward versus trunk tied SRT. To me, that's the hitch with SRT, I don't like doubling the effective force on an unknown TIP while ascending... especially if I don't HAVE to.

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The load on the TIP can be dispersed by spiraling the rope down the tree. I've played around with my 120# scale and seen some amazing reductions with just a little tree/rope friction.

Single Jack did this wonderful illustration.
 

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The SHD bypasses limbs easily compared to other ascenders, it would bypass a crotch about as well.



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What's is the feature that allows that kind of action.

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Only has one handle, there's nothing substantial to catch on the branch and your hand is well protected as you push past.

That makes sense about getting reductions from friction but what happens if the rope leaves the trunk above the wrapping, isn't all that friction negated relative to the TIP and you're back to 2x?
 
It's hard to explain but easy to picture in my head.

The friction must be contributed by the wood the rope is bending over, right? If you wrapped the trunk 20 times and then let the rope pass through mid-air for even a foot before it reaches the TIP... that trunk friction no longer shares the load on the TIP and the weight on each leg is now back in balance at 2X... roughly.

Also, if you have to wrap the trunk and make sure the trunk friction is useful at the TIP, that is, no rope running through free air near the TIP... that's sounds like as much work as isolating a throwline.
 
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...That makes sense about getting reductions from friction but what happens if the rope leaves the trunk above the wrapping, isn't all that friction negated relative to the TIP and you're back to 2x?

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Blink's right. <u>The diagram only addresses the friction at the limb.</u> In that context, ALL the friction from a trunk wrap is to be considered part of the anchor load - even if the rope doesn't leave the trunk. However, there still may be some friction at the limb that reduces the anchor load and thereby reduces the TIP load below 2x.


LIMB FRICTION LOAD ©2009 by SINGLE-JACK, on Flickr
 
You also have to take into consideration angles. If the limb is isolated and both sides are vertical you have a 2x increase at TIP. If you create some angles by NOT isolating the limb you can reduce forces substantially. By doing this you can also create backups. Each scenario is different, I feel I can get higher TIPs by both distibuting the load through several crotches as well as creating backups. If I cant get the arrangment I like from the ground I can always isolate just cinch it off at the TIP using a bowline with a bight and then play around with it when I get up there so I can get my higher SRT distributed TIP.



Being able to access higher TIPs is one of the biggest positives of SRT. A higher TIP is key to easier climbing. I would like to see how DbRT is for TIP access it sounds like DbRT is like a Hybrid 1;1 for Assent and 2;1 for descent. That would mean you are still limited by the addition of friction in the system to your ability to descend. I really want to see how this would work though.
 
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Crawlovers, possibly one of the biggest advantages I can see. In DdRT these can wreck your ascent. In twin, you can look forward to limb crawlovers. Really. You can do &amp; go places with a 4 wheel drive vehicle that you can't with a two-wheel drive. This is sort of like that. Twin can do everything SRT can do, and additionally can do the things it does uniquely well.



Being able to use redirects and drop through natural crotches, like in SRT, &amp; great abilities to set safety through slinged redirects.



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Blinky, sorry I didn't realize SHD was single handed descender, duh. I thought you were saying the exped was better able to go over limbs and through crotches.

But TM seems to be saying this and that is my question. As we all know it is a nail biting moment when you need to ascend against a limb and getting through crotches is even worst. Am I understanding this right? And if so I am interested in what allows this or any handed ascender to do this.

I usually try in some way to push myself away from the limb so as to clear the rope from pressing on the limb and then somehow find a free hand and advance the ascender. Of coarse in a straight ascent I try not to involve crotches but when unavoidable it becomes a struggle (something I try to avoid when hanging on a rope) to manage though but sometime I will retie and go around. Which are energy wasting ventures in the least.
 
I don't own a high end dynomometer. I do own these:

http://www.fsdiscountarchery.com/vikingscalesbypelstar.aspx

as well as a twenty pound fish scale. Using 3mm cord or chainsaw starter rope and small shrubs trees I've set up many mini-rigging and climbing scenarios. Its super simple to make adjustments to rope angles and wrapping when the load weighs twenty pounds and you're standing on the ground. The relative changes in the loads is interesting to see. With no more than a pocket full of gear and a boot you can see the loads change.

I'm never concerned with overloading my TIP. If it isn't stout enough I choose something else. If climbers choose to use SRT they need to be taught all of the nuances and differences between SRT and DdRT. I've seen some SRT being taught by people who don't understand the physics and miss this point. Is this a failing of SRT? Hardly...
 
Adkpk,

I abbreviated Single Handled Dual |ascender| to SHD since I can't type, I was referring to the design. Sorry for the confusion.

It DOES go around branches (I think that's what he means by crawlovers) better because it's more or less one sided with your hand in a good position to pull it away from the branch as you push yourself away with the other hand... no more struggle, or not much of one at least.

Tom,
I wasn't calling it a failing, you do have to select your TIP more carefully with trunk tied SRT though. What I'm thinking is, I can select smaller, higher TIPS by climbing a doubled rope.

I've got a Uni on the way, I'm gonna give SRT another serious try. I'm not likely to get into rope walking though, I just don't like the way it looks... nerdly rather than manly.
 
I rarely ever RW but I use variations on frogwalking.

Nerdly?
Manyly?

HAHAHAHA! All part of industrial design. I am guessing that Rock and his design team will take Morgan's functionality and raise the design a bit for version II.

I don't really change my criteria for TIPs. They have to be bomber. It's rare that I choose an SRT TIP that wouldn't be a trad TIP too. If I need to I use several techniques to add safety factors to the TIP.
 

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