Death Cam: Rebuilding old C4s with cord stems (yes stem, not sling)

Ryan Swanson wrote: A picture of joe shaking his fist at progress

God knows I do love looking at what passes for 'progress' in modern climbing.

Kyle Tarry wrote:

Aside from climbing 2 full number grades harder, doing much bigger and more committing objectives in the mountains, and being kind to follow climbers who don't have exactly the same interests as them, modern climbers are pretty much the same as they were in your heyday.

The average climber is climbing nowhere near two full number grades harder on a demographic basis. And make that the few that actually climb trad and it pretty much goes completely out the window.

As far as 'being kind', exactly when have I been anything but...?

ryanb wrote:

The pdf i posted earlier has flex tests for technora (Bd gemini cord which i don't think is made any more) on page 8:

Thanks. I saw that reference years ago when I was researching high tech cords for Gunks tie-offs on rigid stem Friends. 

You are correct: BD Gemini is no longer available. But the original Gemini was Kevlar. Gemini 2 was something else (maybe Technora). I wrote this sometime before 2013 http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?post=2621289#2621289

So, Tech cord is OK for slinging hexes and rigid stem Friends but not OK for this application?  Maybe because single strand vs loop..

ryanb wrote:Does the CSR reference you found cite similar studies?

This is all I saw there: http://csrbraids.com/index.php/technora-fiber.html

wivanoff wrote:

Thanks. I saw that reference years ago when I was researching high tech cords for Gunks tie-offs on rigid stem Friends. 

You are correct: BD Gemini is no longer available. But the original Gemini was Kevlar. Gemini 2 was something else (maybe Technora). I wrote this sometime before 2013 http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?post=2621289#2621289

So, Tech cord is OK for slinging hexes and rigid stem Friends but not OK for this application?  Maybe because single strand vs loop..

Technora is a blend of aramid fibers and spectra. The idea is that adding the slippery spectra reduces some of the fiber on fiber friction that ends up abrading a degrading the aramid fibers under load. The result is a cord that resists fatigue better than plain aramid but still experiences some fatigue unlike nylon. However, it has very poor strength efficiency when knotted, even with generally high strength knots like double fishermans bend or figure 8.

Typically people use something like titan cord, which is a blend of nylon and spectra, to resling hexes and sometimes cams. I've never seen people using technora to resling anything. 

eli poss wrote:Typically people use something like titan cord, which is a blend of nylon and spectra, to resling hexes and sometimes cams. I've never seen people using technora to resling anything. 

AFAIK, NE Rope 5mm Maxim Tech Cord and Sterling Powercord both are Technora core

eli poss wrote:

Technora is a blend of aramid fibers and spectra. The idea is that adding the slippery spectra reduces some of the fiber on fiber friction that ends up abrading a degrading the aramid fibers under load. The result is a cord that resists fatigue better than plain aramid but still experiences some fatigue unlike nylon. However, it has very poor strength efficiency when knotted, even with generally high strength knots like double fishermans bend or figure 8.

Typically people use something like titan cord, which is a blend of nylon and spectra, to resling hexes and sometimes cams. I've never seen people using technora to resling anything. 

What about Maxim Tech Cord? It's not a blend. And the fact that you have never seen it used for reslinging anything, Maxim suggests it:

"The polyester sheath surrounds a parallel fiber core of 100% Technora, resulting in a cord that gets extremely high tensile strength (3,000 pound tensile for 3mm; 5,000 pound tensile for 5mm). Tech Cord is perfect for balancing anchors and slinging chocks and hexes,"

Basically they contradict everything you said about Technora.  

Kevlar was the fiber that self-abrades in first generation cords like the original BD Gemini. Technora is not Kevlar.

eli poss wrote:

Technora is a blend of aramid fibers and spectra. The idea is that adding the slippery spectra reduces some of the fiber on fiber friction that ends up abrading a degrading the aramid fibers under load. The result is a cord that resists fatigue better than plain aramid but still experiences some fatigue unlike nylon. However, it has very poor strength efficiency when knotted, even with generally high strength knots like double fishermans bend or figure 8.

Typically people use something like titan cord, which is a blend of nylon and spectra, to resling hexes and sometimes cams. I've never seen people using technora to resling anything. 

You pretty adamantly present that as fact, but did you make it up?

According to the manufacturer (Teijin Aramid), Technora is a para-aramid.  I can find no evidence that it is blended with Spectra (an UMPE). A link supporting your position would be helpful

Dynomometer arrived.

I can test some of your theories if ya'll pitch in or send some cord. 

eli poss wrote:

Technora is a blend of aramid fibers and spectra. The idea is that adding the slippery spectra reduces some of the fiber on fiber friction that ends up abrading a degrading the aramid fibers under load. The result is a cord that resists fatigue better than plain aramid but still experiences some fatigue unlike nylon. However, it has very poor strength efficiency when knotted, even with generally high strength knots like double fishermans bend or figure 8.

Typically people use something like titan cord, which is a blend of nylon and spectra, to resling hexes and sometimes cams. I've never seen people using technora to resling anything. 

Idk where you got that information from, but technora isn't a blend, it's still just a para-aramid like kevlar, got this screen shot from one of my books. null

wivanoff wrote:

You pretty adamantly present that as fact, but did you make it up?

According to the manufacturer (Teijin Aramid), Technora is a para-aramid.  I can find no evidence that it is blended with Spectra (an UMPE). A link supporting your position would be helpful

Sorry, my bad, I misread. I was confusing BD's Gemini 1 with Gemini 2. BD Gemini 1 was a blend of aramid and spectra with a polyester sheath. I have been told that pretty much all of the various "tech cord" was the same materials as BD gemini 2, which lead me to believe that technora was the same as BD gemini 2.

"The original Black Diamond Gemini was a different product, similar to Maxim's Spectra-A, and has not been
sold in several years. Spectra-A has a braided Spectra/Kevlar core and a polyester sheath"

from https://user.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf

Edit to add: Technora still has the same problems with fatigue and knot strength efficiency, although not as bad as kevlar.

"Instead, Nylon and the Spectra/Nylon webbing show no drop in strength over the
test, and Technora, Spectra-A, and Vectran all show an immediate and dramatic reduction in strength, but at higher
cycles, the curve flattens and little further strength appears to be lost. Since the effect happens so quickly, a used
piece might show this strength loss everywhere along its length. The knot efficiencies for these materials, which
are very low in new material, may be higher when the cord is used and more flexible, but further testing is needed
to determine this."

Zack P - got the thumb loops thanks! sent shipping $. Thanks! The thumb loop design works perfectly.

The "6mm" dyneema china cord I ordered was more like 8mm so that was a bust.

I hope to do preliminary strength testing this week but I have a crap load of work to do too. Probably need a better cable puller.

What's the status on Death Cam? Eager to see it come together!

Too damn busy with work. Hope to get back to this next week. 

It took more than a week but I finally pulled on a couple death cams. one is a clog cam (similar to size black metolius) retrofit with looped 4mm cord and the other a BD #3 retrofit with single strand tech cord. both showed promise until the boulders they were placed in shifted at around 600 lbs applied tension. Instead of continuing to ruin landscaping I'll have to build an artificial placement out of steel. 

Essentially a DIY UL camalot.

Exactly,  BD Ultralight stem design  (see the patent citations for prior patented cam designs)  However, I do remember seeing an older patent for a cam with a sling stem.  I cannot find it at the moment. 

DrV - I'll pay $100 to you or anyone who finds a previously patented cam with sling or cord stem. Keep in mind, this is not because I think that patent does not exist. I would be happy to pay the $100.

I'll PM you my paypall info ;-)

Balla! payment sent. Ah shit. DrV It'd be fair to pay that back man. The "patent" you refer to is an application- the patent was abandoned.

Aren't you reinventing totems?

https://patents.google.com/patent/US7014156B2