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justthemaid
May 27, 2007, 6:59 PM
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I recently bought a new set of (#1-#5) ballnuts through the mail. I ended up sending one of them back to be exchanged. Mountain Gear exchanged it quickly with no hassles but I thought I would post my observations for educational reasons.
First let me premise by stating that I although I haven't done much welding, I DO have extensive experience at soldering, and have done so professionally for 15 years.
The ballnut I returned seemed to have the following problems:
1) The welds where the cables insert into the head looked bad. Specifically, instead of a nice smooth, welds with the solder flowing smoothly from the cables to the base of the nut, the joint had slightly rounded edges where the cables inserted into the holes. This indicates to me that the nut wasn't hot enough for the welds to adhere properly.
When doing regular soldering, a joint that looks like that can sometimes be cleanly separated from the underlying metal (not good). My concern was that the cables could simply tear out of the head.
Sorry the shadows at the base of the cables make this a little hard to see.
2) You'll also notice the two weep holes on the top surface above where the cables are inserted are not really clean or flush.
3) The nut itself was heavily pitted with tons of inclusions. Maybe a bad casting?
Here's a picture of a good one:
Notice the nice flowing joint that ramps smoothly from the cable to the base of the nut. Not too little and not so much solder that it causes a stiff/weak part at the base of the cables. The two weep holes on the top are smooth and flush. The casting seems cleaner without all the pitting.
Would this piece I returned have had a catastrophic failure? I have no idea. Perhaps not, but why worry about it. It was easier to just exchange it.
This is just a reminder to check any new gear you buy whether it be nuts or cams or whatever.
Stay safe out there.
(This post was edited by justthemaid on May 29, 2007, 2:48 PM)
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iamthewallress
May 27, 2007, 8:42 PM
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Thanks for your post.
I've been trying to take advantage of the whole CCH bruhaha to educate myself a bit more about how gear is put together and what sorts of things are key to look at.
Mal and others with metalurgy experience...what's your take? Since justthemaid's post is the only info I've ever read on such issues, I'm curious to hear other insights.
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bent_gate
May 27, 2007, 9:50 PM
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Very interesting. Anything that gets people to examine their gear is good to see. Though getting educated on what to look for is another issue  I have to say that the pitting seems rather strange on a new piece.
Does anyone know if the ballnutz are either tensile tested or placement weighted for testing before being sent on?
I will be interested to hear some of the responses of others, especially those on the Alien forum who have hands on experience with brazing.
It would also be nice to be educated on what the joints look like if a braze has been fatigued/over-stressed from use. But I'm sure that is way too much to ask for on this site. (but I bet the experts are out there!)
Thanks for posting.
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kimgraves
May 27, 2007, 10:30 PM
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Great post. Thank you.
My question is how did the nut get through QA? If the brazing is being done by hand, why didn't the person doing the work reject it. If it's being done by automation, did no one examine it prior to distribution?
Best, Kim
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maldaly
May 27, 2007, 11:46 PM
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Hey Gang,
As soon as that BallNutz comes back to us I'll pull test it to failure and report back here. I've seen better looking brazes, but I've also seen worse. All of the BallNutz are proof tested to 1/2 their rated strength. In this case that would be to 4kN.
More as soon as we get it back.
Mal
(This post was edited by maldaly on May 27, 2007, 11:50 PM)
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hosh
May 27, 2007, 11:56 PM
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maldaly wrote: Hey Gang, As soon as that BallNutz comes back to us I'll pull test it to failure and report back here. I've seen better looking brazes, but I've also seen worse. All of the BallNutz are proof tested to 1/2 their rated strength. In this case that would be to 4kN. More as soon as we get it back. Mal
I gotta say, the best thing that's come of the AlienGate scandal is the attention that I've noticed from gear companies when stuff like this turns up.
Good on ya Mal for being involved. It gives me confidence in gear when the people making it are willing to accept responsibility when things gunk up.
hosh.
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billl7
May 27, 2007, 11:59 PM
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Hey, I much appreciate it Mal. Thanks!
Alright everyone, we've only got a few days at most to get in our bids. So what is your bid to the tenth of a kN?
My bid: 7.9 kN, although I also would have asked for a replacement. By the way, the braze joints on the five BallNutz I recently ordered look much much better than these; now, they're not quite nuclear reactor quality themselves but pretty close.
Bill L
(This post was edited by billl7 on May 28, 2007, 12:13 AM)
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justthemaid
May 28, 2007, 1:19 AM
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Let me be clear- I'm not trying to slander the manufacturer in any way. I'm a huge fan of these nuts and totally love them. This is the only one I've ever seen that looks even remotely suspect.
I would guess there's enough solder there to hold through some drop tests but nowadays for my $ I'd rather have one that is perfect, not just OK.
(This post was edited by justthemaid on May 28, 2007, 1:23 AM)
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healyje
May 28, 2007, 1:21 AM
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Justthemaid - good eyes. Will be interesting to see what Mal finds out on this one. But Mal has been getting after this and any other problems in the production of Trango products like a bull dog long before this whole affair with Aliens. In fact, the contrast with Trango's standard problem response behavior and ever-evident integrity is just another reason why we know things are a problematic at CCH.
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justthemaid
May 28, 2007, 1:24 AM
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Mal's rapid respose and attention to detail is quite refreshing.
Thanks Mal.
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climbinginchico
May 28, 2007, 1:47 AM
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This is why I love and will continue to buy Trango gear. A good company, with an obvious concern for their customers' safety.
Not only did I read about the #1 Max cam recall, but the day after I saw it on this site I got a little warning slip in the mail from them, I'm assuming because I got mine directly from them as an EP. Even though I inspected it and it looked fine to me, I sent it in. I got it back less than a week after I mailed it, and it was marked inspected and tested, came with an apology and thank you letter, and a little bag of chalk.
Now that I've seen this, I think I will go re-inspect my own set of BallNutz, because I have yet to fall on those babies.
Thanks again Mal, for being super responsive.
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rightarmbad
May 28, 2007, 2:35 AM
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I have 7 of these and like others I immediately went and checked them. They is all lovely. Looking forward to the day of the Trango Alien launch.
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btreanor
May 28, 2007, 3:09 AM
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As I noted over at Supertopo...
Everyone please take note:
(1) Mal's reply:
Hey Gang,
As soon as that BallNutz comes back to us I'll pull test it to failure and report back here. I've seen better looking brazes, but I've also seen worse. All of the BallNutz are proof tested to 1/2 their rated strength. In this case that would be to 4kN.
More as soon as we get it back.
Mal
(2) CCH's reply:
Notice any difference?
There is no failure related to this Ballnut, but Mal is on top of it. We all agree climbing is dangerous, that good (even great) gear can fail under the right (wrong?) conditions. No one (at least not me) is demanding that any other human being be perfect (medical doctors, climbing gear manufacturers, and other high responsibility people are as human as the rest of us).
All I want is for people to try to do what's right--and Mal seems to do that as consistently as anyone I've met.
Brian
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dirtbagger
May 28, 2007, 11:10 AM
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Hi Mal
After having read this thread, I went and checked out my 2 Trango BallNuz I have on my rack and found that the #4 looked a bit like the one posted on here above!
The weep holes are also not fully flush and welds, well I can't really tell if they are good or bad!
Here the pics:
Top
Close-up
Front
Now my question is, from the look of those weep holes, I am a bit unsure if the braze was done well or not? Should I be worried or can I be sure they are ok?
Should I send it in? I bought it 3 years ago or so, from MountainTools website I think!
cheers for your feedback
dirtbagger
(This post was edited by dirtbagger on May 28, 2007, 11:19 AM)
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j_ung
May 28, 2007, 1:08 PM
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I heart responsive gear makers.
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justthemaid
May 28, 2007, 2:36 PM
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It would be interesting to get a little education here from someone who knows more than lil' ol' me, but I'll toss in 2 more cents.
The molten metal wicks down the cable and out the holes. I'll wager a guess that it doesn't have to be completely flush to hold the required kn's if the braze is good.
It's the state of where the cables enter the nut that was more of an issue with mine and all the pitting and bubbling and the slightly rounded edges to the weld meant (in my mind) there was an off chance the metals didn't bond 100%.
Dirtbagger- it's a little hard to see, but your nut seems to have good looking brazes where the cables enter. Although the holes aren't flush I probably wouldn't have returned that one.
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justthemaid
May 28, 2007, 2:39 PM
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BTW. I just made up "weep holes" .
What the hell is the term for those things anyhow, and why the heck doesn't CCH have one drilled in the shaft of their cams? It would solve a lot of their problems.
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maldaly
May 28, 2007, 3:54 PM
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Gang,
I've never brazed anything in my life and all I know about it is what Hugh Banner (RIP) told me one evening over a bottle of scotch. What I gleaned:
- The braze needs to be smooth and even at the joint
- The braze shoudl flow arounf and through the cables
- the braze should completely fill and penetrate through the entire depth of the hole.
The "weep" hole indicates if the braze has flowed all the way into the the hole so a slight bit of a dip or bubbling here is not critical. So the OP's unit with an aberration at the entry point is a bit worrisome to me and that's why I want to test it ASAP.
BTW, the OP returned the unit to the shop where he bought it, adding several days and maybe even a week to the turn-around time. I would love it if people would contact me directly and if there's a real concern I'll give you my FedEx # to get it back ASAP.
Stay tuned....I'll break that BallNutz as soon as I get it back and report.
Mal
(This post was edited by maldaly on May 28, 2007, 4:02 PM)
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anykineclimb
May 28, 2007, 4:04 PM
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Mal,
The Ball(nutz) Breaker!
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dirtbagger
May 28, 2007, 4:26 PM
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Hi Mal
Thanks for the feedback!
Just PM'ed ya, with regards to my #4 Ballnutz
cheers
dirtbagger
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billl7
May 28, 2007, 4:59 PM
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maldaly wrote: Gang, I've never brazed anything in my life and all I know about it is what Hugh Banner (RIP) told me one evening over a bottle of scotch. What I gleaned: - The braze needs to be smooth and even at the joint - The braze shoudl flow arounf and through the cables - the braze should completely fill and penetrate through the entire depth of the hole. The "weep" hole indicates if the braze has flowed all the way into the the hole so a slight bit of a dip or bubbling here is not critical.
In my humble non-brazing-expert opinion, if anyone reads that and still has concerns about their pro they should have the piece looked at by an expert.
justthemaid, Thanks for posting the pictures and for the discussion. That took some care to put together and post - no small thing.
Bill L
(This post was edited by billl7 on May 28, 2007, 6:17 PM)
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the_climber
May 28, 2007, 6:07 PM
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Mal, You da man for the quick responce!
I've always been impressed with Trango gear! In light of all the braising issues with aliens and stuff, and the more common use of gear that is braised (cams, micros,...) I had a thought. Most gear comes with a little pamphlet, would it be possible/usefull to have a picture showing the difference between a good and bad braise in the pamphlet? Just an Idea.
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maldaly
May 29, 2007, 3:17 AM
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Wow!, that's a hell of a suggestion. I'm not sure how inspiring that would be if it came with a piece of gear you shelled out your coin for. Hmmmm. I''ll have to think about that. Keep the good ideas flowing, though.
Mal
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JAB
May 29, 2007, 5:56 AM
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the_climber wrote: Mal, You da man for the quick responce! I've always been impressed with Trango gear! In light of all the braising issues with aliens and stuff, and the more common use of gear that is braised (cams, micros,...) I had a thought. Most gear comes with a little pamphlet, would it be possible/usefull to have a picture showing the difference between a good and bad braise in the pamphlet? Just an Idea.
While more info usually is better, wouldn't it give the picture of Trango pushing over the quality control to the customer?
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bobruef
May 29, 2007, 10:23 AM
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Maldaly and Trango rock! It's responses like this that make me buy trango when I can. Mal is the man!
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the_climber
May 29, 2007, 3:13 PM
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JAB wrote: While more info usually is better, wouldn't it give the picture of Trango pushing over the quality control to the customer?
If it was done in such a manner to show what it is that the quality control people are looking for then no, it could show greater responsibility on the part of the company. Perhaps it could be presented as an inspector looking at then with zoomed in circles of the good and bad.
With all the questions regarding quality control being thrown around latley, showing it in action in not a bad Idea. If not in the pamphlet, then pehaps a section in a catalog or on the web site.
(This post was edited by the_climber on May 29, 2007, 3:14 PM)
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kimgraves
May 29, 2007, 11:30 PM
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the_climber wrote: JAB wrote: While more info usually is better, wouldn't it give the picture of Trango pushing over the quality control to the customer? If it was done in such a manner to show what it is that the quality control people are looking for then no, it could show greater responsibility on the part of the company. Perhaps it could be presented as an inspector looking at then with zoomed in circles of the good and bad. With all the questions regarding quality control being thrown around lately, showing it in action in not a bad Idea. If not in the pamphlet, then perhaps a section in a catalog or on the web site.
I agree with this. Something on the website entitled, "What to look for when inspecting your gear." And a sentence saying, "We are committed to catch all manufacturing defects. However the end user should inspect every piece of gear they buy. Here's what to look for."
It's a partnership - and should be.
Best, Kim
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carabiner96
May 29, 2007, 11:37 PM
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I feel as though a pamphlet would say "We're too lazy and cheap to inspect our gear ourselves, so here's what you do..."
But the website/catalog page is a good idea!
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gunkiemike
May 30, 2007, 12:25 AM
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carabiner96 wrote: I feel as though a pamphlet would say "We're too lazy and cheap to inspect our gear ourselves, so here's what you do..."
Exactly. If it's that easy to SEE a bad unit, then the manuf. has to LOOK AT each piece. It doesn't take long.
Reminds me of those Petrenko cams...
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the_climber
May 30, 2007, 4:26 PM
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kimgraves wrote: the_climber wrote: JAB wrote: While more info usually is better, wouldn't it give the picture of Trango pushing over the quality control to the customer? If it was done in such a manner to show what it is that the quality control people are looking for then no, it could show greater responsibility on the part of the company. Perhaps it could be presented as an inspector looking at then with zoomed in circles of the good and bad. With all the questions regarding quality control being thrown around lately, showing it in action in not a bad Idea. If not in the pamphlet, then perhaps a section in a catalog or on the web site. I agree with this. Something on the website entitled, "What to look for when inspecting your gear." And a sentence saying, "We are committed to catch all manufacturing defects. However the end user should inspect every piece of gear they buy. Here's what to look for." It's a partnership - and should be. Best, Kim
What do you say Mal? Could Trango get something like this going on the Wed site or in the Catalog? I guess it would kinda be an out line of the quality control and what is being looked for in that process, or something along those lines.
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billl7
May 31, 2007, 4:15 PM
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I suspect that your nutz are the reason mgear just asked me to return my new and perfectly good-looking nutz for a pull test to destruction.
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highangle
May 31, 2007, 4:49 PM
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WOW! Mgear is being pro-active about testing like that! First Paul Fish confirms the Alien issue, now he is taking care of this?!! (not saying there is anything wrong with nutz or Trango!)
Glad to send him my business any day!
(This post was edited by highangle on May 31, 2007, 4:50 PM)
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billl7
May 31, 2007, 5:26 PM
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highangle wrote: WOW! Mgear is being pro-active about testing like that! First Paul Fish confirms the Alien issue, now he is taking care of this?!! (not saying there is anything wrong with nutz or Trango!) Glad to send him my business any day!
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adatesman
May 31, 2007, 6:40 PM
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healyje
May 31, 2007, 6:53 PM
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MGear and Trango are simply showing how the real deal conducts their affairs. In days gone by REI or EMS might have played the MGear role - but those days are long gone in another example of the evolving battle between Internet and Big Box retailers.
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justthemaid
Jun 1, 2007, 10:43 PM
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Egads. 
Apologies to anyone who got their gear confiscated. I guess an over reaction is better than the alternative and everyone will love Trango even more for their paranoia.
Typical day in my life. YUP. Caused a nation wide recall today. uh- Oops.
Someday I'll be touring a nuclear reactor and inadvertantly lean on the lever that blows up the city. Welcome to my world..
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billl7
Jun 1, 2007, 11:10 PM
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Hope to return the favor some day.  Perhaps it will be me in the control room.
Shipped mine off today. BTW, I'm pretty certain that the mgear person that called did not use the word "recall". I think it was something along the lines of a request to send them back for testing to destruction due to questionable braze(s) on some others (yours I presume). It seems likely that Trango just wants/needs more data thus far. And for a moment, I did consider refusing to return them - they looked that good to me.
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stymingersfink
Jun 1, 2007, 11:18 PM
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billl7 wrote: maldaly wrote: Gang, I've never brazed anything in my life and all I know about it is what Hugh Banner (RIP) told me one evening over a bottle of scotch. What I gleaned: - The scotch needs to be smooth and even at the joint - The scotch shoudl flow arounf and through the cables - the scotch should completely fill and penetrate through the entire depth of the hole. Well said, succinct summary.
perhaps the scotch has flown around and through the cables, penetrating through the entire depth of the hole (i call my brain).
ok, back on topic.
yeah, mal... when will we be seeing Trango Aliens? At least we know you climb... who knows if D.W. does? (probably not on aliens anymore, if at all!)
WE do appreciate your remaining in contact with the climbing community... your prompt input on issues which may or may not directly impact the company you operate says a world to those of us out here in (real) life.
It should speak to those of us who participate in this (insert objectionable superlative) activity as much as DW's input (or lack thereof) does.
In fact, WE do appreciate how much you have given back to our community year in and year out. It is one of the highlights of my year to see you MC'ing the auction every year down Ouray way. Keep givin' 'em hell, Mal.
again... thanks!
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maldaly
Jun 1, 2007, 11:25 PM
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The Ouray auction is one of the highlights of my year, too. You know I got $10,000 for my "Got Stump?" shirt this year? That makes almost $20,000 total that the ice climbing community has donated in the name of that shirt for operations of the ice park.
bill7, you got it right. After I saw this thread I was just about to pick up the phone to MGear and I got call (or email. I forget) from Eric at MGear. We decided to do this mini-check just to see where reality is. I've pull tested tons of BallNutz to failure and never had a braze blow on the #2-5, regardless of the appearance of the braze. They all break at the carabiner loop. The #1s all pull the braze off the sides, thus the low strength rating.
One of the saddest moments in my career was when Hugh Banner (RIP) and i realized that we wouldn't be able to infuse Scotch into the braze joints of the Brass Offsets. We tried and tried but the stuff would just boil off when the torch hit it. We thought we were on to something when we tried to apply our cold fusion theories to the problem at hand but the scientists at the UU research lab beat us to it. And then it turned out to be a fraud!
Hang in there. I'll be testing next week. In the meantime, I'm off to the SuperTopo beer gathering tonight at the Southern Sun.
Mal
(This post was edited by maldaly on Jun 1, 2007, 11:30 PM)
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mheyman
Jun 2, 2007, 12:39 AM
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Mal,
You’ve managed to make even a mini-recall confidence inspiring and fun!
Course I wasn’t asked to send my Ball-Nutz in.
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billl7
Jul 4, 2007, 1:11 PM
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Bump.
(am curious how the testing is going)
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ncrockclimber
Jul 4, 2007, 4:12 PM
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Mal,
I met you briefly at the NRR, and was impressed with the way that you took the time to answer my questions about Trango gear at your booth. You were patient and really took the time to make sure that I understood the finer point of your product line. Your handling of this issue also impresses me. I like doing business with people who have good attitudes and stand behind their products. For what it is worth, you have won my business, and my next set of draws (not to mentions anything else I need) will be purchased from Trango.
Thanks!
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maldaly
Jul 11, 2007, 7:13 PM
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Hi gang,
BallNutz are in and tested and I'm relieved to say that they all met the minimum spec of 8kN. Sorry this took so long but we had a first order FedEx epic and the units got lost for 2 weeks. It appears that small bubbles or un-conformities in the "weep" holes aren't a strength issue. All of them failed in the cable system somewhere. Pictures below. The far right unit is the one that justthemaid (the OP) returned.
Group shot:
#1 - 10kN Cable failure at thumb loop.
#2 - 8.8kN Cable failure at nicropress sleeve
#3 - 10.4kN Cable failure at braze
#4 - 9.9 kN Cable failure at thumb bar
#5 (original unit) - 8.15 kN Cable failure at braze
BallNuts have always failed in a number of different modes. I wish we could get them all to fail at the thumb loop (In theory the highest strength possible) but it just hasn't happened. I'd also like to see more consistent breaking strengths but with the variety of failure modes we can't do that either. I've always rated BallNutz by the rounding down to the nearest kN from the lowest breaking strength.
Be safe out there.
Mal
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dynosore
Jul 11, 2007, 7:43 PM
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Nice. Can you imagine being in a situation where you took a 8kn fall on a ballnut? Yikes! That'd be a story to tell.....
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the_climber
Jul 11, 2007, 8:03 PM
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Thank you Mal!
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reno
Jul 11, 2007, 9:19 PM
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the_climber wrote: JAB wrote: While more info usually is better, wouldn't it give the picture of Trango pushing over the quality control to the customer? If it was done in such a manner to show what it is that the quality control people are looking for then no, it could show greater responsibility on the part of the company.
I agree with this. Showing folks how to inspect gear isn't a bad move for the manufacturer. I'd view it as "Hey, here's your gear item. We strive to make sure our products are up to snuff, and you should make sure we're doing our job. We have to answer to you, our customer, so if you see something here you don't like, holler and we'll make things right."
That sort of thing.
And it raises awareness, always a good thing. While lots of folks here are diligent about inspecting the gear they use, other people are not: Go to store, buy cam, go to crag, place cam.
Big time kudos to Mal for being a stand-up guy and running an honest, ethical business.
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boku
Jul 11, 2007, 9:23 PM
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maldaly wrote: ...I've always rated BallNutz by the rounding down to the nearest kN from the lowest breaking strength...
Not to complain or anything, but have you considered adopting a 3 sigma rating for the Ballnutz?
I'm no math whiz, but based on the test results here and the Wiki page on Standard Deviation, I get a mean average of 9.45 kN and a standard deviation of 0.839 kN (did I do that right? Anybody?).
According to the BD page on 3 sigma, applying 3 sigma to these test results would yield a rating of of 6.93 kN - say 7 kN if you fudge it upwards just a tiny bit. Of course, this is based on a small set of results that are likely not representative; more extensive testing might result in a very different 3 sigma rating.
Thanks, Bob K.
(This post was edited by boku on Jul 11, 2007, 9:30 PM)
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tinnchris
Jul 11, 2007, 9:41 PM
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STDEV = .938
Yay, I have something to contribute!
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billl7
Jul 11, 2007, 10:02 PM
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Very cool. Glad we all had a nice ending to this story - a credit to Trango for the story and especially the ending. And, I just got a call from Mountain Gear who facilitated the return of the good-looking set I had previously. They conveying the results too. I arranged for an order of a new set.
Bill L
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maldaly
Jul 11, 2007, 10:07 PM
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boku,
There are a lot of different ways to rate things, 3-sigma being a good one. If you want to use it go ahead. I don't like it because with most sample groups all it does is allow a specified percentage of the sample group (about 11 in 10,000 units) to fail below the rated strength. I don't like failure so I use the minimum breaking strength. If I ever test a unit and it fails below the rated strength I'll lower the rating on the whole bunch. Again, using a 3-sigma analysis with most sample groups a single unit that fails below the rating would be unlikely to change the rating. Most industries use a "working load" rating of 25% of average failure rate. I don't like that either. The working load rating for most carabiners would be 6 kN. Back in the good old days, we used average breaking strength. 3-sigma is a huge improvement over that and I like to think that minimum breaking strength is an improvement over 3-sigma.
Mal
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boku
Jul 11, 2007, 10:08 PM
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tinnchris wrote: STDEV = .938 Yay, I have something to contribute!
Hmmm... I wonder where I went wrong?
First, I calculated mean average:
mean average=(10 + 8.8 + 10.4 + 9.9 + 8.15)/5
= 47.25/5
= 9.45
Then I used the mean average to calculate sigma, the standard deviation:
sigma=sqrt(1/5*[(10-9.45)^2+(8.8-9.45)^2+(10.4-9.45)^2+(9.9-9.45)^2+(8.15-9.45)^2])
= sqrt(1/5*[(0.55)^2+(-0.65)^2+(0.95)^2+(0.45)^2+(-1.3)^2]
= sqrt(1/5*[0.3025+0.4225+0.9025+0.2025+1.69]
= sqrt(1/5*[3.52])
= sqrt(0.704)
= 0.839
(This post was edited by boku on Jul 11, 2007, 10:11 PM)
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forkliftdaddy
Jul 11, 2007, 11:51 PM
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An awesome attitude:
maldaly wrote: I don't like failure so I use the minimum breaking strength. If I ever test a unit and it fails below the rated strength I'll lower the rating on the whole bunch.
A bit of history I didn't know:
maldaly wrote: Back in the good old days, we used average breaking strength.
Gulp.
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yokese
Jul 12, 2007, 12:25 AM
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boku wrote: tinnchris wrote: STDEV = .938 Yay, I have something to contribute! Hmmm... I wonder where I went wrong? First, I calculated mean average: mean average=(10 + 8.8 + 10.4 + 9.9 + 8.15)/5 = 47.25/5 = 9.45 Then I used the mean average to calculate sigma, the standard deviation: sigma=sqrt(1/5*[(10-9.45)^2+(8.8-9.45)^2+(10.4-9.45)^2+(9.9-9.45)^2+(8.15-9.45)^2]) = sqrt(1/5*[(0.55)^2+(-0.65)^2+(0.95)^2+(0.45)^2+(-1.3)^2] = sqrt(1/5*[0.3025+0.4225+0.9025+0.2025+1.69] = sqrt(1/5*[3.52]) = sqrt(0.704) = 0.839
That would be the standard deviation of that particular subset of 5 units, but if you want to estimate the standard deviation of the whole "population" you'll lose one degree of freedom:
stdev = sqrt ( SUM[(x-average)^2] / (n-1) )
basically:
= sqrt(1/(5-1)*[3.52]) = sqrt(3.52/4) = 0.938
But of course, for a 3sigma test to be meaninful way more than 5 units should be tested.
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boku
Jul 12, 2007, 12:32 AM
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yokese wrote: That would be the standard deviation of that particular subset of 5 units, but if you want to estimate the standard deviation of the whole "population" you'll lose one degree of freedom: stdev = sqrt ( SUM[(x-average)^2] / (n-1) ) basically: = sqrt(1/(5-1)*[3.52]) = sqrt(3.52/4) = 0.938
Ah, thanks, I'll look into that method.
yokese wrote: But of course, for a 3sigma test to be meaninful way more than 5 units should be tested.
Just so, as I noted in my earlier post on the topic.
Thanks, Bob "BoKu" K.
(This post was edited by boku on Jul 12, 2007, 12:36 AM)
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billcoe_
Jul 12, 2007, 3:55 AM
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Malcom - you rule. I wish you were making aliens.
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justthemaid
Jul 12, 2007, 2:57 PM
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...and the # 5 ballnut lived happily ever after as it rode off into the sunset.
It's wires were frayed but it's love for Trango was strong.
After all... tomorrow is another day.
*(fade to silhouette of ballnut standing in the sunset)*
(This post was edited by justthemaid on Jul 12, 2007, 2:59 PM)
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papounet
Jul 12, 2007, 11:25 PM
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maldaly wrote: boku, There are a lot of different ways to rate things, 3-sigma being a good one. If you want to use it go ahead. I don't like it because with most sample groups all it does is allow a specified percentage of the sample group (about 11 in 10,000 units) to fail below the rated strength. I don't like failure so I use the minimum breaking strength. If I ever test a unit and it fails below the rated strength I'll lower the rating on the whole bunch. Again, using a 3-sigma analysis with most sample groups a single unit that fails below the rating would be unlikely to change the rating. Most industries use a "working load" rating of 25% of average failure rate. I don't like that either. The working load rating for most carabiners would be 6 kN. Back in the good old days, we used average breaking strength. 3-sigma is a huge improvement over that and I like to think that minimum breaking strength is an improvement over 3-sigma. Mal
Common misconception that is worth challenging.
choosing the minimum breaking strength from a sample as the boundary of the whole population is not good or bad per se. It is dowright dangerous if the samplesize is small relative to the population. It could be superior to sigma based method if the ratio sample size/population size is large.
There is a definite probability that if the total population follow a normal distribution, that there will be a certain number x biners in THE TOTAL POPULATION failing below the minimum breaking strength observed in a sample.
This probability is dependant on the size of the population and of the sample.
with values 10; 8,8; 10,4; 9,9. 8,15
the stddev of the sample is 9,84 (it is only an estimate of the standard dev of the population)
the average of the sample is 9,45
the 3-sigma value is 6,64
99,85% of biner picked randomly from the population are at least stronger than 6,64kn
but only
91% of biners would be at least stronger than 8kn.
we are far from the minimum breaking strength of 8 kn you found from the sample and that you quote
If we enlarge the sample to 50 with the same values from 10,4 to 8,15, the 3-sigma lower limit is 6,91
if we enlarge the sample size to 500 with the same values from 10,4 to 8,15, the 3-sigma lower limit is 6,93
it is true that on large sample size relative to the population, it is possible to have one outlier in the sample such as one out the 500 which fails at a value lower than the 3 sigma
if the total sample size is = to the population size, the probability is near certainty that that there will be between 0,1% and 0,2% below average - 3stdev
Unless you are willing to share the population and sample size, i dare say that i would take the minimum breaking strength rating with a grain of salt.
Because it is not economically sound to have large sample size in destructive testing, in the absence of complete knowledge, 3-sigma and 6-sigma would appear to be safer than the observed minimum breaking strength.
in fact, I am almost certain that having the actual population and distribution characteristics, under the hypothesis of normal distribution, one can compute the equilibrium sample size for which there is a high confidence (99,5% for example) that observed minimum breaking strength is equal to the average-3estiamted standard deviation
On a related note, it is often the law that defines a Safety factor. In Life-protection-Equipment, the Safety factor can be 4 or 5.
Meaning that equipments are designed to sustain a Maximum Load 4 or 5 times larger than the Working Load (a load in normal operation).
Thus the use of steel biners in some rescue settings.
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the_climber
Jul 13, 2007, 4:52 PM
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Papounet, I think you missed much of what Mal was saying. Perhaps lost somewhere is the translation? I don't know. I would think Mal is mentioning a simplified/dumbed down (ie. stating without unnecessarily complicating the issue with to much detail) rundown of different types of safety ratings.
Ie. the construction and trucking industries require the Chain be rated by a safe working load of aprox. 25% of the breaking strength. I have however seen 70proof chain break at surprisingly low forces in 4x4 recovery. His reference to biners seems only to use an arbitrary piece of gear which, we as a climbing community, can relate to.
Ratings based on both standard deviation and minimum breaking strength are simply other ways of rating safety equipment. They happen to be the two which likely have the most relevance to real world climbing situations. But that’s my opinion. I have used standard deviation calculations in many situations, but relating to ore body concentrations and Paleoclimate calculations. So I’m not unfamiliar with the way sigma ratings work. And I’ll admit it works good with rating climbing gear. If it didn’t I’m sure a reputable company such as BD wouldn’t use it. I do have to side with Mal on the minimum breaking strength stand potentially having greater real world relevance to climbing. Yes it requires a large sample base, so does 3-sigma, to get accurate data on a specific batch. However, it does appear that Mal has no issued with destroying gear for the sake of safety. Quite simply the way he has handled this issue with the Ballnuts is an example one of the most responsible manners with a potential gear problem/issue has been handled with in recently (I’ll add OP with the link-cam to that list too).
The fact that should the minimum failure on a batch of gear be lower, but still within reason for climbing gear, Mal rates the gear at a lower strength shows great responsibility on the part of Trango. (I think this is what you were saying Mal, correct me if I’m wrong about the lower rating thing please)
When it comes down to it, it becomes a personal preference as to what ratings you trust in. I trust the safety of Trango gear just as much as any other brand of gear on my rack. It is amazing gear, if it wasn’t I wouldn’t use it. The same can be said for every piece of gear on my rack.
I guess this is where I stop rambling on and get back to work.
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shogun
Jul 13, 2007, 5:23 PM
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billcoe_ wrote: Malcom - you rule. I wish you were making aliens.
what bill said!
thanks malcom!
-=g=-
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the_climber
Jul 13, 2007, 5:31 PM
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shogun wrote: billcoe_ wrote: Malcom - you rule. I wish you were making aliens. what bill said! thanks malcom! -=g=-
One more vote for Trango Alien-like cams!
C
mon Mal PLEASE!
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stymingersfink
Jul 13, 2007, 6:23 PM
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the_climber wrote: shogun wrote: billcoe_ wrote: Malcom - you rule. I wish you were making aliens. what bill said! thanks malcom! -=g=- One more vote for Trango Alien-like cams! C mon Mal PLEASE!
A TrAli-en-ago cam?
Yeah, I'd be down with that... especially the hybrid version
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ktb
Jul 13, 2007, 7:02 PM
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Wow - good stuff to read in this thread! I will definitely work Trango into my next gear purchases. Hopefully someone like Mal will buy CCH and improve the production process. Could we start a petition! Pass the hat to help fund the buyout :) ?
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maldaly
Jul 13, 2007, 9:50 PM
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I LOVE you guys!
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fear
Jul 14, 2007, 2:24 AM
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ktb wrote: Wow - good stuff to read in this thread! I will definitely work Trango into my next gear purchases. Hopefully someone like Mal will buy CCH and improve the production process. Could we start a petition! Pass the hat to help fund the buyout :) ?
You mean actually HAVE a production process. And no more smoking weed whilst brazing.
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papounet
Jul 14, 2007, 2:29 PM
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the_climber wrote: Papounet, I think you missed much of what Mal was saying. Perhaps lost somewhere is the translation? I don't know. I would think Mal is mentioning a simplified/dumbed down (ie. stating without unnecessarily complicating the issue with to much detail) rundown of different types of safety ratings. ... When it comes down to it, it becomes a personal preference as to what ratings you trust in.
This is where I jumped in with Mal and i jumped in again with you.
The relative merits of the minimum observed breaking strength and 3sigma based values is not a place for OPINIONS.
Provided that the population's characteristic follows a normal distribution, there is a definite mathematical function that describe the probability that one item has a specification lower than a arbitrary value (and especially one computed on a sample.).
let n be the sample size
let p, be the population size
let v1= minimum breaking strength observed
let v2= observed mean - 3 observed standard deviation
for a small sample size, the probablibity that the value of a random item v =< v1 is higher than the probability that v =< v2,
for a very large sample size, the reverse.
one can compute the equilibrium n for a given p, that will give identical probability to both events
(it is equivalent to compute the Probability that v1=v2)
My objection is with OPINIONS on the merits of which rating to use. There is little room for OPINIONS when statistics are considered. The 2 ratings are only equivalent for a certain range of n and p. in other cases, one is superior to the other, which can be computed.
Due to the costs of destrructive testing, I am doubtful that a manufacturer would have the large sample size that would make minimum observed a better predictor than mean-3stddev.
I doubt also that the climbing items from a small scale manufacturing process follow a normal distribution.
I am happy with ratings on 3sigma combined with exhaustive non destructive testing to 50% as this later test would most likely catch the outliers.
ignoring the relevant data from Trango, i can only accept the minimum breaking strength on their products with a grain of salt (and I would suggest that Trango double check the legalese around the statement).
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frodolf
Mar 4, 2008, 1:11 PM
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A bit of thread revival here, but I think this is relevant to the discussion.
I got a set of Trango Ballnutz a few weeks ago and being an aid climber, and having heard so much good about them, I joyfully went out to test them on the rock. It took me two minutes to break one.
What happened was that I bounce tested the smallest one. It wasn't a too hard a bounce test and my weight is in the neighbourhood of 75kg (150lbs). It broke at the "clamp" that keeps the two wires attached to each other (I don't know the word for it in english), which the spring rests on, above the coloured bar of the clip-in/thumb hole. The "clamp" simply blew apart. And I wasn't using too much force. I've bounced micronuts with half the rating just as hard. My estimate is that I created between 1,5 and 2kn of force.
It wasn't a lifethreatening breakage: the wire didn't brake or anything. But that "clamp" is what keeps the spring from being torn apart. Next time I hang from it will be the last. And that sucks. And what's even more stupid is that the clamps on all the five sizes has the same width, so they all have this same weakness. I still keep them on my rack, but I dare not bounce test them at all hard, and I don't care much for falling onto them. I regard them as bodyweight placements for now, sort of.
Thing is I ordered them from the States to Sweden and the shipment was a hazzle and took weeks, so I don't feel like returning it - it'll take mounths! And as I said, I don't trust any of the ones in my set, so in that case I'd like to/had to return the whole bunch. I'm not sure the retailer is up to that. I would't suprise me if they're not.
Has anyone had the same problem? Or am I simply unlucky? (or both)
And how could that peice get through security!?
F.
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the_climber
Mar 4, 2008, 3:46 PM
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frodolf, I would contact Trango directly on this one. Mal is great to deal with as are the rest of the Trango staff.
I've bounce tested the smallest two ballnuts HARD, and never had an issue I also took a short daisy chain fall on one without any incident like your describing. I'm much heavier than you too... about 75lbs heavier.
You don't have to send them back right away then wait, but I would start by calling trango directly and talking to them. Let them know what's up and perhaps get some photo's and let them know to expect them via email or something.
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moof
Mar 4, 2008, 5:54 PM
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Yeah, what the_climber said, contact Trango. The owner, Mal, posts here as maldaly. He is a good guy and will treat you right.
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maldaly
Mar 5, 2008, 5:27 AM
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Hey Frodolf, that nicropress shouldn't have broken. PM me and I'll take care of you.
Mal
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CCEbeling
May 26, 2008, 5:44 AM
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The folks at Trango are really great to deal with. I had a cinch fail to lock out last year when i was climbing in a gym, resulting in a 30-ft ground out. Being on the sharp end of the rope i didnt know if the fall was a result of device failure or belayer error. I called trango and they were happy to inspect and pull test the device and send me a new one. After inspection and pull testing it was determined it must have been belayer error as there was nothing wrong with the device.
I bring this up now because i believe I have discovered the way this accident happened. My climbing partner and i found a way of holding a Cinch at your right hip that prevents lockout, you may already know about this Mal but i think it is something that should be included in the warnings that accompany the product. I will take some pictures and post them as well as PM Mal.
I also found that lockout can be delayed if the belayer grips the rope above the device (a stupid thing to do anyway but in a panicky situation it happens) so it is best to keep hands away from the rope above the device.
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maldaly
May 26, 2008, 3:13 PM
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Hey CCEBeling, in part because of your near miss, we posted video instructions for the Cinch and many other of our products on the website. Check them out at:
http://www.trango.com/videos.php
Climb Safe,
Mal
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billcoe_
May 26, 2008, 3:43 PM
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frodolf wrote: .... I joyfully went out to test them on the rock. It took me two minutes to break one. What happened was that I bounce tested the smallest one. It wasn't a too hard a bounce test and my weight is in the neighbourhood of 75kg (150lbs). It broke at the "clamp" that keeps the two wires attached to each other (I don't know the word for it in english), which the spring rests on, above the coloured bar of the clip-in/thumb hole. The "clamp" simply blew apart. And I wasn't using too much force. I've bounced micronuts with half the rating just as hard. My estimate is that I created between 1,5 and 2kn of force.
First of all, and this might sound like bagging on you, but I'm not trying to disrespect you: however, in this country, it "wasn't too hard of a bounce test" isn't a scientific term and isn't really even repeatable by you. I've had one of these pull out on bodyweight that I thought should have held, but that conveys very little to the reader. What does that mean, "I pulled one with body weight"? I weighed @150 lbs back then. It really means very little.
Furthermore: I don't know how you can "..estimate is that I created between 1,5 and 2kn of force" unless you've tryed doing something similar on a calibrated tester in the same location. Falling on gear even a short distance can easily create very high forces. I'm not saying that you didn't create a low force, but that a higher force than you quoted would be easy to get to with even a short pull test.
Rock and Ice tested toprope falls and MEASURED forces as high as 1300 lbs, which surprised them and everyone else. I use my ball nuts ocasionally, and if I am forced to use the little ones, I make an attempt to back them up as soon as possible, as we all should. I just used the #1 last weekend on a short new route that went free, but if thats all that will fit, it is a great tool to have. My only compunction on using them on a FA instead of fixing a pin or using a bolt, is that now pretty much everyone who follows will need that piece.
I appreciated that you could break one of these and that you shared it, but just to let you know, you are not the first and I suspect you will be far from the last. I'd be interested if someone could find and show some of those short fall force tests that have been done, which may surprise you at how high a force you can get with a short daisy fall.
Anyway, take care all
Bill
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frodolf
May 26, 2008, 7:50 PM
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A bounce test isn't a scientific term in my country either, duh. Tell me of one place where it is. And it wasn't my intention to be scientific.
My estimates of the force I created are, as you point out, dubious. I didn't have any intruments on me at the time to register the exact force. Sorry. But it was pretty much the kind of bounce test that breakes the wire of a #1 copperhead, a wire that is rated to the vicinity of 1,5-2,0 kn. Hence my estimation.
There is a difference between ripping a piece and breaking a piece. Mine broke, no question about it, in a way it wasn't supposed to. But I must say – and it has been my intention to post it here a while – that the service from Trango was great! I sent them some pictures and they sent my a new bullnut, totally free. Sweet!
F
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stymingersfink
May 26, 2008, 7:51 PM
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maldaly wrote: Hey CCEBeling, in part because of your near miss, we posted video instructions for the Cinch and many other of our products on the website. Check them out at: http://www.trango.com/videos.php Climb Safe, Mal
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jt512
May 26, 2008, 8:12 PM
Post #75 of 78
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maldaly wrote: There are a lot of different ways to rate things, 3-sigma being a good one. If you want to use it go ahead. I don't like it because with most sample groups all it does is allow a specified percentage of the sample group (about 11 in 10,000 units) to fail below the rated strength. I don't like failure so I use the minimum breaking strength. If I ever test a unit and it fails below the rated strength I'll lower the rating on the whole bunch....I like to think that minimum breaking strength is an improvement over 3-sigma.
The minimum observed strength is not an improvement over 3-sigma. I suspect that by using the minimum observed strength your intention is to be more conservative than using the 3-sigma strength. However, if your sample size is not large enough, then the observed minimum strength will likely be greater than three sigma. Conceptually, this is easy to see: the smaller the sample of units tested, the less likely it will be that the sample will include units with unusually low strengths. In particular, since less than 1 unit in 700 will be weaker than -3 sigma, it is clear that all the observations in a small sample will likely be greater than -3 sigma. Hence, a rating equal to the minimum observed strength will likely be greater than -3 sigma.
Of course, if your sample size is large enough, the situation reverses: the larger the sample, the more likely that the sample will include a unit that is weaker than -3 sigma, and hence, the observed minimum strength will likely be the more conservative rating.
So, how big a sample size do you need to be confident that you are being more conservative than 3 sigma? Since the units tested are a random sample, there is no sample size that guarantees that the sample will include a unit weaker than -3 sigma; hence, you can never know for sure whether you are being more conservative or not. However, we can easily calculate the probability that a sample of size n includes a unit weaker than -3 sigma.
The probability of a randomly selected unit's strength being less than -3 sigma is approx. .00135. Hence, the probability p that a sample of size n includes at least one unit weaker than -3 sigma is given by the following formula:
p = 1 - (1 - .00135) ^ n.
Using the above formula we see that if you have tested n = 100 units, then the probability p that at least one of the units in the sample is weaker than -3 sigma is .126; that is, there is only a 12.6% chance that a sample of 100 units includes a unit at least as weak as -3 sigma. If you've tested 200 units, you still only have a 23.6% chance of having a minimum observed strength greater than -3 sigma. Want a 50/50 chance? Test 513 units. 75% chance? Test 1026 units. 95% chance? Test 2218 units. So, to be reasonably confident that your minimum-strength rating is less than -3 sigma, you have to test a pretty big sample.
Mal, you say that the 3-sigma system "allows" [13.5] units per 10,000 to be weaker than the rating. The fact is, though, that any reasonable rating you give to a piece of gear, there will always be a non-zero probability that a piece of gear will be weaker than the rating. What the 3-sigma rating does is admit this, and quantify what that probability is. Thus, when we buy a 3-sigma rated product we know exactly how reliable the rating is. In contrast, when you use a minimum observed strength rating, the customer does not know how reliable the rating is. As we see from he above math, the rating may be higher or lower than what the 3-sigma rating would be, depending on the number of units tested. By using this method you are actually giving the customer less information about the the minimum breaking strength he can expect than you would by using a 3-sigma rating, unless, of course, your sample sizes are quite large.
Finally, the expected value of the minimum observed strength decreases as the sample size tested increases. The more you test, the lower your ratings will have to be. No matter how many units you have tested, if you keep testing long enough, you will eventually find a new weakest unit, and have to lower the rating. Truncating the rating down to the next whole kN mitigates this problem. If you're lucky, your weakest observed unit breaks at "something".9 kN and you may never in the future observe one that breaks at less than "something".0 kN so your rating lasts forever. On the other hand, if your weakest unit was observed to break at "something".1 kN, you will likely have to drop the rating by a full kN eventually.
If you don't think that a 3-sigma rating is conservative enough, a more effective approach than using the minimum observed strength would be to simply use an n-sigma rating, where n is a number greater than 3. A 4-sigma rating would mean that 1 unit in 32,000 would be less than the rating. For 5-sigma, the figure jumps to 1 in 3.5 million; and for 6-sigma, it's a whopping 1 in 1 billion.
Jay
(This post was edited by jt512 on May 26, 2008, 10:42 PM)
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CCEbeling
May 26, 2008, 8:53 PM
Post #76 of 78
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Registered: May 26, 2008
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In reply to: Hey CCEBeling, in part because of your near miss, we posted video instructions for the Cinch and many other of our products on the website. Check them out at: http://www.trango.com/videos.php Climb Safe, Mal
Those are great video's, you should print a link to them on the tags of the products, i think video instruction is a great tool to show people how to use products safely. Its quicker and more clear than reading materials. Just make sure people know where to find the videos
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maldaly
May 26, 2008, 10:31 PM
Post #77 of 78
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Registered: Oct 31, 2002
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Each product has a direct link to the videos as well.
Mal
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snowboardercolo
May 27, 2008, 2:01 AM
Post #78 of 78
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Registered: Jul 19, 2007
Posts: 87
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Hey Mal.
The videos are great! Thanks!
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