alien pull test

[Adam]

http://www.youtube.com/watch?v=cj-vwEYMAS8
http://www.youtube.com/watch?v=2BPyniSqeBc&NR=1

not sure if this is a certified test or not but it's convincing!

[The Mitt]

That doesn't mean crap to me. The company is run by a dick, there have been so many quality assurance mistakes why take the risk. Great design crap company.

Mitt

[Adam]

yup, it's hit or miss whether you have a good one... but if you do you're set!

[The Mitt]

Sure, but how do you know for sure you got a good set? a bad braze can hold a couple hundred pounds but won't hold even a small fall. Also why support a guy who knows he is selling a potentially dangerous product but took 3 more accidents before he did anything about it? Even blamed one of the accidents on the guy who fell saying it was a fraud. Then his QA (quality assurance) is so bad there was a fourth bad cam reported.

The best thing that can happen is no one buy his cams he hits chapter 11 and a reputable company buys the design from him.

Mitt

[Shawn B]

I've got a set and I "think" I trust them. They are old though...before the quality issues started. Would I make a 3 piece gear anchor out of Aliens only....hmmm...prob not unless it was the only option. I'm waiting for the new Metolius cams to come out next spring. I think they'll be the cat's @$$...and from a good solid company.

[Adam]

you bounce test them.

[Fred]

aside from cams breaking and people dying am I the only one who thinks the design is terrible? I find them so limp it's like trying to push a rope up the wall...

[The Mitt]

you bounce test them.

Bounce test? Hows that for a factor 1.5 fall or more? That is probably one of the most unreliable ways to test if a piece is good or not. Maybe OK for a placement but not a piece of gear. The only way to know for sure is send it to an indepandant lab for a pull test. That would probably cost as much as the piece.

M

[Adam]

That is probably one of the most unreliable ways to test if a piece is good or not.

what's your reference on that?

a static bounce test puts a tonne of force on the piece... much more than you realize. the stretch in the rope reduces the forces immensely.

i'm no expert, just speaking from experience.

[granite_grrl]

That is probably one of the most unreliable ways to test if a piece is good or not.

what's your reference on that?

a static bounce test puts a tonne of force on the piece... much more than you realize. the stretch in the rope reduces the forces immensely.

i'm no expert, just speaking from experience.

So you don't know how much force a bounce test will put on a cam either....yet you are telling people its an adequate test? Nice to meet you Kettle.

The majority of Aliens are rated to 12kN. BD supposedly pull tests all their gear to half their rated strength. Perhaps a bounce test could get close to 6kN, but that does seem rather high.

Nope, I don't have the date either about how much force a bounce test generates. But the end result is that I don't feel like I should have to test all my own gear to verify that it's safe. To me the onus should remain on the manufacturer.

I agree about the new Metolius cams coming out. I've heard that they look pretty sweet!

[chossmonkey]

That is probably one of the most unreliable ways to test if a piece is good or not.

what's your reference on that?

a static bounce test puts a tonne of force on the piece... much more than you realize. the stretch in the rope reduces the forces immensely.

i'm no expert, just speaking from experience.

Clip a screamer between the piece and your aiders and bounce away. Let us know if you can generate the 500 pounds needed to activate it.

My bet is no.

On the off chance you can get it to start ripping, attach another (in parallel) so it will be 1000 pounds. If you can get that to start ripping then you are on your way to a reasonable test.

[Burley]

1kn = 225 lbs of force

Depending on your weight I think you can get close to 2kn of force with a bounce test.

Force Calculator:
http://www.myoan.net/climbart/climbforcecal.html

Here is what I read once... and found it again...
"A dynamic climbing rope must be designed to absorb enough energy so that the maximum force on an 80 kg. (180 lb.) climber in a factor 2 fall is not more than 12 kn. (2698 lb.). The maximum force on a top anchor could approach 19.9 kN or 4475 lbs."

http://www.southeastclimbing.com/faq/fa ... .htm#climb
http://www.southeastclimbing.com/faq/faq_kilonewton.htm

[The Mitt]

That is probably one of the most unreliable ways to test if a piece is good or not.

what's your reference on that?

Common sense, force calculator, experience, many websites and books (supertopo, RC.com, how to climb aid) you pick.

a static bounce test puts a tonne of force on the piece... much more than you realize. the stretch in the rope reduces the forces immensely.

i'm no expert, just speaking from experience.

No your wrong again, a static bounce test does not put a tonne (2k pounds) on a piece unless your much heavier than the average human. You might get 800-1000 pounds if your lucky. This still may be held by a bad braze. Notice I said "may" because no-one knows how much a bad braze will hold (Russ Walling reported that one Alien he tested broke at 900 pounds). So you bounce test get 750 pounds (arbitrary number) on the gear but it breaks at 1500 (arbitrary number). Good test? I don't think so. I to am not an expert and my numbers may be off by allot, but I am not giving advice for testing suspect gear.

So how to do test at home? The answer is you don't cause you probably don't have the expertise or equipment. If you read RC.com people discuss dumbass ideas like pull on it with your car or use a vice and a come-along. Now how do you know you didn't just break your piece that your testing, how do you measure the force you put on it?

So your stuck with climbing on them or not. Your choice and your risk assessment. Telling people that bounce testing them is OK is just dangerous.

I don't use them but I really like the design. I think its important that people learn as much as they can about CCH Aliens and make up their own minds. I personally don't trust them and don't use them.

Mitt

[chossmonkey]

So how to do test at home? The answer is you don't cause you probably don't have the expertise or equipment. If you read RC.com people discuss dumbass ideas like pull on it with your car or use a vice and a come-along. Now how do you know you didn't just break your piece that your testing, how do you measure the force you put on it?

With Screamers you could measure pretty closely how much weight you put on it. You would need several loaded together (parallel) to get to a reasonable force before the stitching starts to rip. Yates Screamers reliably deploy at around 500 pounds. Three should get you to 1500. With a come-along you could slowly apply force until the first stitch or two blows on each. Unweight and test the next with the same Screamers, they shouldn't start to rip again until you get back up to whatever force you are testing to. If you only rip a few stitches testing one or two units the Screamers should still be okay to use as they were intended on manky gear.



Unless someone weights 250 pounds I still think it would be pretty tough to get to 500 pounds with a simple bounce test. You'd need to start taking short falls onto the piece and at that point you'd likely start hurting yourself.

[chossmonkey]

Not that I would climb on them anyway.

[Adam]

chill out there hurricanes

i never said that a bounce test will mean that it is free of defects, i meant it is adequate for me (plus having taken falls on them) and meant the colloquial 'tonne' not literal. that should probably have been inferred from the 'i'm no expert' part. static pulls are violent but no, aren't equal to a f2 fall unless you drop a large weight, which doesn't necessarily have to involve dropping a human's weight

[STeveA]

Force from a bounce test is about 1.2 Kn or 270 lbs.

[Adam]

moreover, i actually meant this kind of bounce test

[Matt Peck]

Adam you dog

[martha]

[Burley]

Bounce test doesn't tell you much... other than will this fail (gear or rock) under my body weight?... force produced is too small. I think Steve and I are using the same math for the force from a bounce test... kn = (climber weight+gear) x 1.5 / 225.

I'm sure your bang on Steve. Whether the force from a bounce test is 1.2 or 1.8 doesn't matter all that much to me. My weight produces less than 1kn of force and me bouncing would be closer to 1.2 than 2, but a 220 lb person with 10lbs of gear that does a serious bounce test can get close to 2... My math shows 1.6... that's close to 2. I wanted to error on the high side of the force produced when I said 2kn... I do understand the physics behind force a bit... I only wanted to show that a bounce test isn't going to get you close to 6kn... or the force of a normal fall (reasonable fall)... which I think is around 6kn. We can get all crazy in and say "that the force calculator doesn't take into account slack, friction, the belay, and blah blah"... I say What is important is that a bounce test on a placement won't get you close to the force of a fall when you have 35 feet of rope out and fall 5 feet above your gear.

I'm not an engineer, but my calculator works.

[*Chris*]

A question...
If you're serious about a home-made test of your aliens I wonder if there's a few things you could do to increase the force produced from a typical static bounce? For instance, how about

1) rigging several climbers together on a single bounce. (the holly-bag comes to mind)

2) setting up the test such that you take advantage of predictable force multiplication that occurrs in anchors built from pieces separated by large angles?

3) bouncing off of a z-pulley system built from static materials

[The Mitt]

I don't think I would test at home. most tests that could be done with the gear I have may be more destructive than a valid test.

I would suggest the rule for all other gear applies. If in doubt throw it out. Why place a piece of gear that you think in the back of your mind may not have been built properly?

M

[Holly Reid]

1) rigging several climbers together on a single bounce. (the holly-bag comes to mind)

HAHAHAHAHA

[Makwizard]

I am currently conducting research at Duke University to analyze and redesign cam lobes. The end goal is to improve a cam's ability to hold in soft rock and flaring cracks. I have just begun my research but will be continually posting updates of my findings on my cam research page.

Thanks.