Blown wire on #1 BD Stopper

[korup]

Aiding Iron Horse yesterday, I had total cable failure on a brand new #1 BD nut under BODYWEIGHT (195 lbs; nut is rated to 2 kN, 450 lbs). The cable failed at the bend (biner junction, not the swage). Piece was pull tested 3 times, and then weighted- has anyone ever observed failure like this before?????

[Alex]

i've only seen the cable break on a really short leader fall, not under body weight

[catbirdseat]

Time to go on a diet. But seriously, it's possible one side got more stress than the other because of the position of the piece. Any number of factors could weaken it from it's rated strength.

[JosephH]

Bill Coe and I found a fairly new #1 BD stopper with a blown wire on a route last year. Looked like someone had an unhappy experience on it. Not sure exactly what "pull tested 3 times" means mechanically, but it is quite easy to blow these pieces. I've typically used a pre-sliced Air Voyager (pre-Screamers) when I'm using these sizes of pro. In general I wouldn't test these babies very hard.

[chris]

Did you just pull test it, or did you bounce on it too? I'd imagine it wouldn't be too hard to reach cable failure if you bounced on the piece, even if it wasn't intentional.

[korup]

Nope, no bounce testing, just three sequentially harder pulls with a runner.

[Alpinfox]

 

 

I was initially even more shocked by this, but I just read that #1 stoppers are only rated to 2kN (~440lbs). I'm still surprised though - especially that it failed at the cable rather than the stopper itself shearing which is how I've always imagined those small stoppers failing under heavy loads.

[lancegranite]

Most of the time, undamaged wire rope fails at the nicosleve.

Edited July 5, 2005 by lancegranite

[catbirdseat]

Seems to me that the use of stainless steel thimbles on the wire loop would be a good idea on the smallest wire sizes. Thimbles serve to increase the radius and reduce point loading.

 

[Szyjakowski]

Most of the time, undamaged wire rope fails at the nicosleve.

does that make brassies better if they are attached into the chockstone part?

[billcoe]

Use of thimbles would increase the strength, but would also dramatically increase the weight of a piece which normally stays in the basement.

 

Black diamond says batch testing ensures consistent quality, plus each unit use to be individually tested to half its rated strength before leaving the factory.

 

Perhaps a smaller radius carabiner means you do not get close the full tensile rating they came up with?

 

? What was the carabiner you used?

[Bill_Simpkins]

I've bounce tested a #1 stopper on several occasions with no failure. I weigh 200 pounds.

Must have been a bad nut or weird loading.

[korup]

'biner was a BD ovalwire, no burrs or other damage. I, too, assumed either the nut would shear out, or the swage would separate before actual wire failure...

[lancegranite]

Bad nuts indeed!

There is no way to say how strong a piece is going to be in the field.

Those guys can pull test in the shop all day long...

but everything goes out the window the minute you place them.

 

[JosephH]

I should add that the one we found was also blown at the bottom of the clipping loop. 2kn is not a hard number to reach and I likely wouldn't bounce or hammer test a #1.

[flyingkiwi1]

I managed to blow the wire on a #2 stopper a few years ago. We had meandered off up some old aid route towards the top of Beacon, reached a section with some hard moves protected by what I thought was a bomber placement. It was a bomber placement. Sadly, I forgot about metal fatigue. I think the wire blew on my third try at the sequence; the first two falls had been less than 10'. The last one was significantly longer. I called BD (not really to complain, just to tell them what had happened) and they sent me a new nut.

[chelle]

Korup - have you contacted BD about the failure? They'd probably love to analyze the piece and may even send you a new one.

[korup]

Just sent 'em an email. We'll see, eh?

[Szyjakowski]

if they don't give you a new one, what does a stopper cost. 7$...oh no. I think i found a few this year.

[archenemy]

Black diamond says batch testing ensures consistent quality, plus each unit use to be individually tested to half its rated strength before leaving the factory.

 

Perhaps a smaller radius carabiner means you do not get close the full tensile rating they came up with?

 

The BD factory does batch test, but I don't think they test each piece.

MEC--I don't remember seeing them test each piece, but I do remember batch tests. Do you remember something different?

 

The tensile rating is for the maleability of the metal-and each rating should be applicable for its corresponding piece.

 

MEC--Help out here-what would Big Bill say here?

[Thinker]

[mec]

That is correct, BD only batch tests their stuff. long gone are the days of looking at each and every piece before it went out the door.

 

The tensile rating of each piece is a combination of things. The malleability of the actual stopper is one. The yield strength and size of the wire, and any stress concentrations acting on the wire (bends, crimps, etc, those little thimbles would help out). And the method used to close the loop. The small pieces are affected more by the wire size. The stress concentrations are roughly the same.

 

The malleability stays the same throughout, but the effect is increased since the piece is so small, a bit of deformation can more easily cause the piece to lose its grip, but the piece itself will not 'fail'.

 

Overall, I am surprised the stopper failed, but as we all know batch sampling will not catch 100% of faulty. Batch sampling with good process control does catch the big majority of them, so in general there is nothing to worry about.

I am sure with a good email and sending the piece back to BD, they will replace it.

[archenemy]

That is correct, BD only batch tests their stuff. long gone are the days of looking at each and every piece before it went out the door.

 

The tensile rating of each piece is a combination of things. The malleability of the actual stopper is one. The yield strength and size of the wire, and any stress concentrations acting on the wire (bends, crimps, etc, those little thimbles would help out). And the method used to close the loop. The small pieces are affected more by the wire size. The stress concentrations are roughly the same.

 

The malleability stays the same throughout, but the effect is increased since the piece is so small, a bit of deformation can more easily cause the piece to lose its grip, but the piece itself will not 'fail'.

 

Overall, I am surprised the stopper failed, but as we all know batch sampling will not catch 100% of faulty. Batch sampling with good process control does catch the big majority of them, so in general there is nothing to worry about.

I am sure with a good email and sending the piece back to BD, they will replace it.

 

Yeah, that's what I thought.

 

And how do they get those really big airplanes to stay in the sky?

[mec]

Airplanes are lighter than air of course.

[korup]

Yeah, I could care less about a free stopper, I'd rather it never happened...the 25+ footer was "interesting."