lowest diameter for pull cord

[lofty]

what would be the lowest diameter for a pull cord for a 120 or 200 ft rope ? Would a 5mm accessory cord ( type found at rei ) do ? or do I need something more specialized. I have my ropes but so far friends always had the pull cords... time to buy my own and I would like to go as light as possible.

thanks :)

[Iceaxe]

I use a 6mm pull cord, the reason being is I feel safe enough rappeling on a 6mm cord in an emergency and I think its nice to have that option if needed. YMMV

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[lofty]

which cord do you buy ?

[Iceaxe]

I use Imlay (Tom's) ropes and pull cords as they are hard to beat for the price.

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[denaliguide]

I've used this as a pull cord and as an emergency rappel line for years. 5mm and 5000lb test.

http://www.backcountrygear.com/maxim-tech-cord.html

[Mountaineer]

I've used this as a pull cord and as an emergency rappel line for years. 5mm and 5000lb test.

http://www.backcountrygear.com/maxim-tech-cord.html

Excellent. That is what I use. Very strong, light, resistant, and I would rap from it in an emergency. It has worked in even the hardest situations. Although it has a tendency to tangle more than other pull cords (bit stiff); so a rope bag can help.

I also have used a 4mm accessory cord for shorter/clean pulls, but wouldn't recommend it as a best practice. There are many who swear by a 8mm (or 6mm if you are comfortable and experienced with that small of a rope) so you have something useful to rap from if your other rope is compromised, stuck, or needs to be extended. It is great to go light, until you get into a situation that wasn't planned for...

[Iceaxe]

There are many who swear by a 8mm (or 6mm if you are comfortable and experienced with that small of a rope) so you have something useful to rap from if your other rope is compromised, stuck, or needs to be extended.

What do you mean 8mm in an emergency..... 8mm was my standard rope for years.

FWIW: Now I use Tom's 8.3 Fire (which is noticably larger diamenter then my older 8mm stuff I was getting from anther source).

[reflection]

Canyon Pull Cord.

For years, a decade back, most used a 6mm NYLON accessory cord. The line was fairly supple, easy to use, but it stretched big time on long pulls and the sheath wore easily. Not a good back up for rapping. Often used for prussic building.

Rope makers then began to use various alternatives to "accessory cord" nylon. Poly/nylon mix, Poly/poly and then technora/poly or technora/nylon. Other variables exist. The poly and the technora have a more "static" feel and have less stretch; some have a much stronger sheath and some are marketed as rope vs accessory cord. I have an esprit 6mm line that is a poly blend, stiff static rope" that is used as a pull line, and also has been used to rap on. I've NOT tried the Maxxim mentioned above. May be an ok option? I've seen expensive 3mm line that is light and small.

Tom's Imlay 6mm line is poly sheath, poly core. Static feel, light/minimal stretch. I've used the product - for price and quality it's A-1. It's going to weigh more and stuff larger though than the 5mm mentioned above - I don't know the properties of that line though and don't know how it is rapping.

So, with the modern evolution of ever increasing outdoor product available, I'd AVOID a full nylon accessory cord, and probably go with the Imlay product, or maybe the Maxim above? Cost, weight, size, potential use as backup, stretch, wear, water saturation? Long ago I tried some pricey 4 & 5mm for a while and then went back to 6mm.

[ratagonia]

I've used this as a pull cord and as an emergency rappel line for years. 5mm and 5000lb test.

http://www.backcountrygear.com/maxim-tech-cord.html

Yeah? Don't do that.

Before the Internets (therefore, not easy to google), Sandy Stewart did a test of aramid-core "rope" as he was thinking about using it as fixed line in the Himalaya. Might be something in Rock and Ice, about issue 20...

Sandy Stewart: http://www.rockandice.com/articles/h...256-first-lady

(Aramid = a class of materials that includes Kevlar and Technora)

Aramid-core ropes have a significant problem, which is why you won't see many (any?) around. When you flex it, it abrades against itself and destroys itself. So while it is 5000 lbs strong when fresh off the spool, after 10 rappels, how strong is it?

My memory (always suspect) is that Sandy rappelled on it 100 times, then went and tested it, and it held 200 lbs. In other words, he is lucky he did not die (or get hurt) in the testing, because the core was gone.

The Aramid-core cords were originally made for slinging chocks, where they are not subject to flexing.

Gemini cord was developed by my pal Chuck Brainerd at Chouinard equipment to get around the self-abrading problem. Gemini cord has both aramid and spectra-like in the core, the spectra-like being self-lubricating and acts as a lubricant for the aramid. Also lighter. A better "power-cord", but the time the differences were pertinent passed 2 decades ago.

Tom

[ratagonia]

I've used this as a pull cord and as an emergency rappel line for years. 5mm and 5000lb test.

http://www.backcountrygear.com/maxim-tech-cord.html

Hmmm...

This might be of interest:

http://www.backpackinglight.com/cgi-...tml?startat=30

QUOTE: "This website inspired me to buy 10 foot lengths of several ropes and tech-cords and test their abrasion resistance.

My test rig differed somewhat from the link above. One end of the rope was attached to a secure anchor 10' above the ground. To keep the rope under tension, I tied into the other end so that I was suspended 3' above the ground. I then measured the time/sweat required to saw through the rope with a blunt rock.

The 5 mm maxim tech cord (polyester cover, technora core) was disturbingly easy to saw through; much easier than 8 mm perlon. The polyester cover provided marginal abrasion resistance, but the technora core cut like a hot knife through butter."

[Mountaineer]

The Aramid-core cords were originally made for slinging chocks, where they are not subject to flexing.

Tom

Great response and insight here. Continued flexing will damage these types of ropes. From Comparative Testing of High Strength Cord by Tom Moyer, http://user.xmission.com/~tmoyer/tes...ength_Cord.pdf:

"The decrease in strength with use is a worry forany of the Technora, Kevlar or Vectran materials. The Gemini and the Spectra-A are also extremely stiff and
difficult to tie and untie. An 18 -foot piece makes a bulky object hanging from the harness. They make excellent
chock cord (where a stiff cord is desirable), but would make a poor cordelette. Among the high-strength cords,
Titan seems to be the most suitable material for cordelettes. The Ultratape is even better, and the webolette is an
elegant solution to multi-point anchors, although we'd prefer to see slightly higher strength on the single-strand
arms. Last, Nylon cord and webbing may be the best of all. Although heavier, they are cheap, strong, universally
available, and seem to have a virtually unlimited flex life."

[Mountaineer]

From Comparative Testing of High Strength Cord by Tom Moyer, http://user.xmission.com/~tmoyer/tes...ength_Cord.pdf

Note that according to this study, the Technora drops really fast in strength after just a few flexes, but then tapers to a "steady state" breaking load of 2000 lbs even after continual flexing.

[denaliguide]

oops

[denaliguide]

@ratagonia thanks for the links. that is good to know. the rock and ice link though just seemed to be about catherine freer. did i miss something?

[lofty]

Thanks everyone for all the insight....Decided on Tom's 6mm pull cord. :) Now I just have to mosey on south, pick up my gear and do some canyons.

cheers,
lofty

[ratagonia]

@ratagonia thanks for the links. that is good to know. the rock and ice link though just seemed to be about catherine freer. did i miss something?

It was the first google result for Sandy Stewart, who was mentioned as doing Choalotse in there. Just trying to make it clear Sandy Stewart had some bonafides as a climber, though certainly lesser-known.

Tom

[moab mark]

YMMV but myself and most of the people I go with just bring double the rope. May have a couple of shorter working ropes to tie together for a pull on a long rappel but I do not see the savings in weight and space worth the risk of getting stuck if your ONE rope goes south. Plus you can rig multiple rappels with your extra ropes etc. Someone smarter then me should start a poll on using a pull cord vs rope.

[Iceaxe]

For me it depends.... some times you need to save weight.... ever done Heaps as a pair? I have... and every ounce saved counts when you are hustling 600' of rope through a difficult canyon.

Now if you have an abundance of horsepower than by all means carry real ropes.

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[Brian in SLC]

6mm is a nice size. Imlay looks like a great deal. Best for the money IMHO.

Had the Espirit and still have the bits of it (rock fall damage). Liked it.

I think I'm using a BW searchline in 6mm. 2500lbf. Great hand. Gettin' a touch fuzzy as I've used it a bunch. Mo spendy.

[ratagonia]

oops

I realize it is against the Bogley style-guide to provide actual vetted information, but -

I sent in a question to New England Ropes, and here is the reply:

Hello Tom,

While all aramid fiber ropes loss strength due to flex fatigue, depending on the type of aramid fiber used in the cord, the rate of strength loss will vary greatly.
Kevlar and Twaron have very poor performance regarding flex fatigue, where as Technora is substantially better.
Additionally there are various grades of Technora with differing / improving degrees of fatigue resistance.
TechCord uses the cordage grade of Technora with it's improved fatigue resistance.

As a result when the USArmy was testing aramid cords in an effort to choose an Emergency Rappel cord, they choose Tech Cord.
While Tech Cord (with it's Technora core) out performed other types of Aramid fiber cords, please note Emergency Rappel means just that, Emergency only.
And as such our recommendation is that the line be retired after 10 rappels.

Thankyou for your interest in the product
Best Regards
Steve Parola

From: Tom Jones [mailto:canyoneeringusa@gmail.com]
Sent: Tuesday, September 04, 2012 6:21 PM
To: NERopes Mail - Inbox
Subject: Rappelling on Tech Cord

On the Page: http://www.neropes.com/product.aspx?...1&lid=3&pid=66

You list "Emergency rappel" on the page for the Tech Cord.

I am surprised. I am under the impression that aramid-cored "cord"
loses strength very quickly under the flex conditions of rappelling.
Do you have lab data showing that the Tech Cord maintains sufficient strength after (say) 200 rappels by a 200 pound person on a single line? Or something like that? Would you like to share that lab data with me so I can share it with the world?

Thanks -

Tom Jones
Imlay Canyon Gear
(AND former New Englander)