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Chockstone Forum - Gear Lust / Lost & Found

Rave About Your Rack Please do not post retail SPAM.

 Page 3 of 4. Messages 1 to 20 | 21 to 40 | 41 to 60 | 61 to 72
Author
anchor testing rig
widewetandslippery
17/09/2010
8:57:44 AM
Long live bob the robot.
widewetandslippery
6/10/2010
11:20:58 AM
http://www.supertopo.com/climbers-forum/1283274/SS-Chain-Shackle-Hanger-Tests
GPage
7/10/2010
12:53:41 AM
Hey Mike i have my rig up and running,it's pulling about 85 kn, so far I have been using 10mm stainless quicklinks for attachment, they have been pulled to 75kn trying to destroy my ringbolts,bolts stretched but wouldn't break,quicklinks stretched but are still useable, I have also pulled 8mm stainless anchor chain to 75kn it stretched but didn't break, I have busted some biners with it they have been breaking around double their rating.
I have rendered a 16mm stainless D shackle un-useable pulling to 75kn,can't get the thing to unscrew now!
mikllaw
7/10/2010
8:47:38 AM
email me a picture
One Day Hero
7/10/2010
1:08:06 PM
On 7/10/2010 GPage wrote:
> I have busted
>some biners with it they have been breaking around double their rating.

This should make you immediately suspicious. I'm not saying it isn't right, but a number of biners holding double what they're rated makes me go "hmmm"

ambyeok
7/10/2010
2:46:08 PM
I say we have an anchor test rig showdown. We hook up mikl's to gpage's and place bets on which breaks first. Now thats real science.

edit: on reflection, due to interweb impersonality that does come across a bit harsh... just poking fun

tmarsh
7/10/2010
3:30:06 PM
I suppose if they were industrial items and stamped with a safe working load (SWL) then it's conceivable that they would fail at twice the rating, but climbing gear? A little surprising.
PDRM
7/10/2010
5:38:50 PM
All you materials scientists: is there any difference in the difference in breaking force with slow (static) vs rapid (dynamic) loading? I can see that for some items, forged gear for e.g. there might be?

P
mikllaw
8/10/2010
9:38:46 AM
On 7/10/2010 PDRM wrote:
>All you materials scientists: is there any difference in the difference
>in breaking force with slow (static) vs rapid (dynamic) loading? I can
>see that for some items, forged gear for e.g. there might be?
>
>P

The answer is probably no but, like most of this stuff, it’s complicated. There are differences in material behaviour at different strain rates, most metals and plastics increase their yield strength at high strain rates, sometimes this means the material changes failure mode from a ductile failure to a brittle failure (at a higher load). However the strain rates have to be very high (~ loading to failure in < 1/100th of a second) before there’s any significant difference. The strain rates you can get when the force is transmitted through a climbing rope are generally low (unlike if you fell on a cable).

One reason people tend to think of dynamic loads as being destructive is the hammer analogy, the hammer is just a convenient way of concentrating energy built up over the swing into a short time. There are also all sorts of dynamic effects with using ropes that add little peaks to the load as load pulses hit the ends and bounce back.

A few groups in the US use drop towers which are good at seeing what loads the ropes put on the gear. There is already a lot of data on that, ropes keep stretching up to their impact force, unless of course you have them through a belay device:- belay plates etc just slip at about 3kN, Grigris and other autolockers slip at 9kN (hence you never use them on trad).

So, for most realistic loads, no. Falling on a sewn spectra sling rather than a climbing rope with knots, stretch, and a belay device will obviously generate much higher loads, but the gear will behave in a similar way; except that it may break……
GPage
9/10/2010
1:17:20 AM
The main reason I set up this rig was to be able to test my ringbolts to failure so that I could then offer some kind of rating, as an example if my rings broke at 50 kn I'm not going to rate them at 45 kn I would allow a big safety factor and rate them to 20-25. I sent some to mike and he tested to 40 kn with no sign of stretching or failure so the 75 kn is very probable seeing as the have stretch quite a bit.
The ram I bought was sold as a 10 ton ram(98kn), my calculations of the pressure surface would mean it has a 1.4 mm thick wall to produce 10 ton at it's max pressure rating. I don't believe the wall would be that thin so I have based my calculations on a 3mm wall , thus reducing the max force of the ram to about 90kn, not 85 as I first posted. So if anything the figure should be slightly higher if I were to accept the manufacturers specs.
I will send you a pic in a couple of days mike.
GPage
9/10/2010
1:25:49 AM
Mike also told me that an unwelded ring will open at about 7kn which rang true in my tests and and a faders mini biner(12 kn) failed at 13 kn in my test.
mikllaw
11/10/2010
12:52:46 PM
could you send me your calculations please.
I'm still having trubbl putting load bearing end fittings on mine, they are tapered pressure fittings!
One Day hero
11/10/2010
5:39:40 PM
On 9/10/2010 GPage wrote:
>The ram I bought was sold as a 10 ton ram(98kn), my calculations of the
>pressure surface would mean it has a 1.4 mm thick wall to produce 10 ton
>at it's max pressure rating. I don't believe the wall would be that thin
>so I have based my calculations on a 3mm wall , thus reducing the max force
>of the ram to about 90kn, not 85 as I first posted. So if anything the
>figure should be slightly higher if I were to accept the manufacturers
>specs.

???????????

How are you measuring the maximum force a biner holds before it snaps? I'm thinking that there is a needle pointing at a bunch of numbers somewhere as all this pressure surface crap seems totally irrelevant. If you don't have a needle pointing at a scale, you don't have much of a testing rig!

Are the numbers your needle points at kilograms or pounds? I don't believe climbing biners holding double their rating, sorry.
One Day hero
11/10/2010
6:22:47 PM
On 11/10/2010 davidn wrote:
>Needle? Testing rigs have moved a bit beyond that nowadays I think. As
>in they test the force applied to the object hundreds, thousands or more
>times per second and produce a graph of load over time.
>
>Whether Mikl and Gpage are using such a force gauge would be good to know
>though?
>
Well, Mikl's rig has a needle, I've seen it! So maybe you ain't so smart as you think, Dave.

After that paragraph of psychobabble which Gpage wrote, I have no idea what he's measuring with.......but I'm pretty sure its wrong!

>Also worth noting that for those manufacturers using 3sigma (DMM, Black
>Diamond, some others), they have confidence that 99.7% (or more) of products
>won't break within the noted range. That doesn't say when it will break.

More psychobabble. There is no "noted range", there is a single strength value. Almost all the biners will break above the stated value by a little bit..........double is not a little bit!

> Verification of tests is always good either way.

Ooh, thats a good idea, glad you pointed that out
One Day Hero
13/10/2010
7:41:57 PM
On 12/10/2010 davidn wrote:
>I give up. I know when I'm wasting my time, and talking with you really
>is a waste of time.
>
>You're right ODH. It is as you say it is, because you said it is. Cheers.

Don't spit the dummy dave, explain to the good people of chockstone what "the noted range" actually means, with respect to carabiner breaking strength. I'm dying to know
One Day Hero
13/10/2010
8:21:24 PM
Hang on, I worked it out. By "noted range" you mean "from 0 - breaking strength"!

An odd way to express it, but now it makes sense.

How big do you reckon the standard deviation is? Gpage said he had a couple of carabiners breaking at double their rated strength....what are the odds that they're both from the strong end of the bell curve?
One Day Hero
13/10/2010
8:33:08 PM
Hey Cogsy, you pulled your post! I saw it though, allow me to answer.

When I was testing bolts in my former job, we attached to the bolt a pulling device which incorperated a measuring device (yes, it had a needle).

We then applied a gradually increasing force with the pulling device whilst measuring that force by watching the little needle on the measuring device, until the bolt failed. (actually, we didn't bust the bolts most of the time.....but you could do so, by the same method).

Now, call me backward, but this seems like the sensible way to test the strength of individual bolts. Can you please explain how using "pressure surface gradient interface calculations" makes this rather simple task any simpler/better/more sciency?
GPage
14/10/2010
11:41:15 PM
The following is a photo of my test rig depending on the exact use i have a few variations but this is where i tested the carabiners.



As you can see I have a needle thingy,also known as a pressure gauge,which is where the whole pressure surface becomes rellevant, as this and mikes rig read the force in pressure PSI which then needs to be converted into force.
#1- you need to know how many inch2 the PSI is working on.
#2- inch2 x psi ="X"lbf
( 1000lbf=4.482216 kn)
#3- "x" divided by 1000 x 4.482216= The force applied in kn

I have no reason to think the rig isn,t working properly , all components have been purchased new, and as i said crappy little faders biner with a rating of 12kn failed at 13, No disrespect to Mike but i'm sure that if my name was Mike Law you would have believed everything i posted!
And if you guys had been where i was standing today and saw the size of the test boulder which actually started shifting on me you wouldn't doubt the workings of my rig for a second! I had to stop doing tension testing for my own safety.
I don't understand what is so hard to understand about a biner breaking at double it's rating,it's called a safety factor, this allows for discrepencies in manufacturing and materials etc. My take on the rating is that it would be a max load which would still leave the piece in perfect working order, Not to far after the rating is where extreme deformation started to take place in my tests and once this type of deformation has occured the piece would be rendered useless.

Just shoot me an email Mike outlining what calculations you need.
GPage
15/10/2010
11:24:35 AM
The other thing to take into account is the type of force applied. This type of rig applies static force, which in my opinion would probably allow a higher test rating than dynamic force( involves acceleration). This opinion is based on the fact that it would allow the metal to deform over a longer period of time thus allowing it to stretch rather than tear.
After going over my calculations i was actually right origionally to say that my calc of a 3mm wall was about 85kn( 83.267) total for the rig.The 90kn calc was inbetween the 2.(i miss read my notes)

Manufacturers specs would have a pressure surface- 2.21829 inch2 - 1000psi=9.9428549kn
3mm wall -ps- 1.857723 inch2 - 1000psi=8.3267157kn

I do have video documentation,but am unable to load them at this point as my computer was worked on recently and am having trouble finding the program disk.
All biners were in good order most had seen extremely minimal use( mate bought them and hardly climbed), all puchased new about 2003/04 except faders alloy screw i'm guessing 2000/01 had more use but not significantly worn.

Faders steel screwgate 34kn-(OG 12kn)-( standard issue toprope biner)- significant stretch after 4000psi- failure at approx 7100psi- failure due to gate key pin extraction. Held 2400psi after fail.

Kong hms alloy screw(keylock) 22kn-(OG 8kn) Significant stretch after 2000psi- failure 6100 psi-failure due to keylock sidewall blowout- held 2000psi after failure.

Petzl spirit keylock 23kn-(OG 9.5kn)- significant stretch after 2400psi- failure at 5500psi- failure due to keylock fail causing terminal spine failure.

Faders pearshape alloy screwgate 20kn(OG 6kn)- significant stretch after 2400psi-failure at 5600psi- terminal failure at spine,gate mech stayed intact.Gate pin quite bent would have failed soon after.
One Day Hero
15/10/2010
1:08:20 PM
On 14/10/2010 GPage wrote:
>As you can see I have a needle thingy,also known as a pressure gauge,which
>is where the whole pressure surface becomes rellevant, as this and mikes
>rig read the force in pressure PSI which then needs to be converted into
>force.
>#1- you need to know how many inch2 the PSI is working on.
>#2- inch2 x psi ="X"lbf
> ( 1000lbf=4.482216 kn)
>#3- "x" divided by 1000 x 4.482216= The force applied in kn
>
Those calcs seem reasonable, but something is messing with your results.

I reckon you need to calibrate! I know its a pisser of a thing to do (we used to send our testing rig off for calibration once a year)......you gotta have an accurate, calibrated conversion from pressure to force, otherwise.......???????


>I have no reason to think the rig isn,t working properly

Testing 2 biners to double their rating is a good reason to think exactly that

>No disrespect to Mike but i'm sure that
>if my name was Mike Law you would have believed everything i posted!

If Mike had gotten those results I doubt he would've believed himself!

> I don't understand what is so hard to understand about a biner breaking
>at double it's rating,it's called a safety factor, this allows for discrepencies
>in manufacturing and materials etc.

It's hard to believe because every other test has biners breaking around the rated load!

My take on the rating is that it would
>be a max load which would still leave the piece in perfect working order,
>
No, its a failure rating. If the biner is still in one piece it hasn't failed. Think like a gear company, they want to sell stuff which means getting the biggest number possible on the lightest biner........there's no way the marketing department will allow deliberate under-rating while every other company is printing failure load

How about lifting your car to calibrate? Get manufacturer's spec's on how much the car weighs, then hook it up.......post photos!! :)

 Page 3 of 4. Messages 1 to 20 | 21 to 40 | 41 to 60 | 61 to 72
There are 72 messages in this topic.

 

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