aramid fiber and bridge failure

texasmossball

texasmossball

Location
central texas
I recall a few years back someone posted some pics of a replacement bridge where the core had totally failed but the sheath showed no signs of wear. The person said it was some kind of high tech fiber, aramid I think, but I don't remember exactly what kind, and now I can't find the post. The rope was lime green and blue.

I remember that the consensus was that this type of rope should not be used for bridge material because the fibers could "cut each other" when put in a tight bend AND movement situation such as when used as a saddle bridge.

My question: Unless I have hallucinated all this, does that risk not still exist? I see where rope with core (and sheath) fibers like vectran and technora are being used in such apps as ring loops on friction savers for instance. Seems that would be the same exact type of stress on the rope.

So, is there a higher risk of rope damage/ failure when fibers of this type are loaded and reloaded when used in these types of apps vs. plain ol' polyester?
 
As much as aramid is a good strong rope, the problem is uv degradation.

I make foot loops out of aramid (kevlar) it is great for that as its extremely light wieght and thin,rated at 10kn.

The use should be limited to one year or thereabouts.

I have made bridges out of vectran, strength is good but again limit it to 1yr use.

Best bridge I have made was out of dyneema,with webbing chafe cover.
 
[ QUOTE ]
I see where rope with core (and sheath) fibers like vectran and technora are being used in such apps as ring loops on friction savers for instance. Seems that would be the same exact type of stress on the rope.

So, is there a higher risk of rope damage/ failure when fibers of this type are loaded and reloaded when used in these types of apps vs. plain ol' polyester?

[/ QUOTE ]

Vectran and Technora are the culprits as neither is very good at withstanding flex fatigue (or "self-abrasion"). This is not the same as simple loading and unloading. The forces on a bridge are very unusual, as the center of the bridge experiences repeated bending and straightening as the ring or biner slides back and forth. Dyneema is excellent at withstanding this sort of flexing, but not Technora or Vectran. Where repeated flexing is not occurring, both fibers should be fine. But don't use them in a bridge.
 
As far as I've heard from companys working with Technora and Kevlar, UV Degradation is not a big problem, or at least self abrasion is the much bigger one.
But no still data for all this.
UV is a problem vor Vectran and especially for PBO (which is the strongest, most static and most expensive of all them). But thats irrelevant for Tree Climbers, I know.

This reminds me of another thread I started a while ago, unfortunately with not much response...
http://www.treebuzz.com/forum/showflat.p...true#Post351999
 
:birra:
That Marlow link is great. It's the only useful thing Tuttle has ever done that I know of.
Once, he had a post that talked me into milking my entire rope towards a splice because it was supposed to make driving the splice home easier.
 
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