http://ozreport.com/forum/viewtopic.php?t=31432
Free* weak link tensile testing.
Orion Price - 2013/03/16 00:31:26 UTC
I have a 10kN (2,200lbf) tensile tester at my disposal.
- That somebody else designed and built, right?
- 10 kiloNewtons are equal to 2248 pounds force.
- Good thing you have something that can do over seventeen times what Davis and Rooney have been forcing everyone to use since the beginning of time and the maximum allowable weak link for the new and improved Lockout Mountain Flight Park aerotow release.
- 320 pound glider, two point bridle - 3910 pounds towline, 12.2 Gs.
Mail me your links, and I will test them.
And let's not worry about the bridle material and diameter - 'cause what difference could those issues possibly make?
- Thanks for that photo. It must've taken you hours to set it up and edit it so's everyone can understand what he's looking at.
- Of what POSSIBLE USE...
Dr. Trisa Tilletti - 2012/06
We could get into details of lab testing weak links and bridles, but this article is already getting long. That would be a good topic for an article in the future. Besides, with our backgrounds in formal research, you and I both know that lab tests may produce results with good internal validity, but are often weak in regard to external validity--meaning lab conditions cannot completely include all the factors and variability that exists in the big, real world.
...could any of your lab testing be? You and I both know that lab tests may produce results with good internal validity, but are often weak in regard to external validity--meaning lab conditions cannot completely include all the factors and variability that exists in the big, real world.
The * after the "free" is a stipulation. Disclose all relevant information about the link...
Except, of course, for the bridle material and diameter - 'cause what difference could those issues possibly make?
...and let me publish the data for everyone to enjoy.
- If you look at the Davis Show weak link poll results it looks like the overwhelming majority of AT clones are enjoying their Davis Links so much that any more enjoyment would probably overload their systems and kill them.
- We solo guys are permitted use of only two pieces of fishing line - the 130 pound Greenspot that was the perfect standard aerotow weak link for over twenty years and the new unidentified 200 pound orange stuff that's been the perfect standard aerotow weak link for very special pilots - those willing to use the Dragonfly three strand tow mast breakaway protectors as their effective weak links - at a couple of operations since last year.
SURELY those have been THOROUGHLY tested by these fine professional establishments and have met their expectations of breaking as early as possible in lockout situations but being strong and reliable enough to avoid frequent breaks from turbulence.
So what would be the point of testing anything else?
That's it. All it costs you is a envelope.
And an stamp.
Want to try a different knot?
Why? We already know two techniques for positioning the knot so that it's hidden from the main tension in the link and excluded altogether from the equation. Thus...
- A loop of 130 pound Greenspot will be able to hold to 260 pounds when you want it to hold in turbulence but can, when it senses the pilot is in danger from a lockout, direct the main tension to the knot and cause the pilot to be released when the weak link is loaded to 130 pounds and before he can get into too much trouble.
- And, as of last year, likewise a loop of the new 200 stuff will be able to hold to 400 pounds when you want it to hold in turbulence but can, when it senses the pilot is in danger from a lockout, direct the main tension to the knot and cause the pilot to be released when the weak link is loaded to 200 pounds and before he can get into too much trouble.
What to try a new material?
- Sorry, I'm having a little trouble understanding that sentence.
- Want to try a new material? Does it meet the definition of...
http://ozreport.com/forum/viewtopic.php?t=31052
Poll on weaklinks
Jim Rooney - 2013/03/04 19:31:36 UTC
The accepted standards and practices changed.
...an "accepted standard or practice" - read a Rooney Link or, with their permission, a new Morningside Link? If not...
http://ozreport.com/forum/viewtopic.php?t=30971
Zach Marzec
Jim Rooney - 2013/02/11 09:13:01 UTC
Hey Deltaman.
Get fucked.
Jim Rooney - 2013/02/15 06:48:18
Yeah, sorry... nope. Not behind me at least... go be a test pilot behind someone else.
Jim Rooney - 2013/02/17 00:34:14 UTC
The onus is on YOU.
Not the other way around.
"We" don't need to justify jack.
Jim Rooney - 2013/02/17 10:37:47 UTC
You're hear to argue. Plain and simple. I've got better stuff to do.
Go blow smoke somewhere else. I couldn't give a rats ass... I won't be towing you so what do I care?
http://ozreport.com/forum/viewtopic.php?t=31052
Poll on weaklinks
Jim Rooney - 2013/03/05 21:40:02 UTC
I'm sorry that you don't like that the tug pilot has the last word... but tough titties.
http://ozreport.com/forum/viewtopic.php?t=30971
Zach Marzec
Jim Rooney - 2013/03/07 18:24:58 UTC
You're the one advocating change here, not me.
I'm fine.
http://ozreport.com/forum/viewtopic.php?t=31052
Poll on weaklinks
Jim Rooney - 2013/03/10 05:35:17 UTC
So as much as you want to jump up and down and rave about how it's "Your choice!!!!"... too bad. It's not. You're on my rope.
Jim Rooney - 2013/03/11 02:21:14 UTC
If I'm not happy with your gear... for whatever reason... too bad.
...how's it gonna get airborne?
- Wanna try something heavier than a Dragonfly three strand tow mast breakaway protector? Why bother?
What happens when you use two links?
We already know that. Twice as many weak links...
http://www.hanggliding.org/viewtopic.php?t=27393
Pro towing: 1 barrel release + weak link or 2 barrel release
Juan Saa - 2012/10/18 01:19:49 UTC
The normal braking force in pounds for a weak link is around 180, at least that is the regular weak link line used at most aerotow operations. By adding a second weak link to your bridal you are cutting the load on each link by half, meaning that the weak link will not break at the intended 180 pounds but it will need about 360.
I made the same mistake on putting two weak links thinking that I was adding protection to my setup and I was corrected by two instructors on separate occacions at Quest Air and at the Florida RIdge.
...twice the required breaking strength, twice the danger to the pilot. Pretty simple arithmetic, really.
What about old links?
We already know that too. Have for a long time...
Donnell Hewett - 1981/10
In skyting we use a simple and inexpensive strand of nylon fishing line which breaks at the desired tension limit. There is no possible way for it to jam and fail to release when the maximum tension is exceeded. Sure, it may get weaker through aging or wear and break too soon, but it cannot get stronger and fail to break. If it does break too soon, so what?
http://4.bp.blogspot.com/-bRrpHNa68iY/UQ6Pv9gRZyI/AAAAAAAAjTg/Hc22bx5122Q/s2048/20943781_BG1.jpg
We simply replace it with a fresh one.
They just get safer and safer.
You will know.
- Surely they know already. I mean, wouldn't the people who've been perfecting aerotowing for twenty years have tested every suitable material and configuration one could think of? In addition, of course, to the Industry Standard single loop, three-strander, and double loop they use for all solo gliders, all Dragonflies, and all tandem gliders respectively?
- And do WHAT with that information? One has to know what a weak link IS before one can start making any halfway intelligent decisions about installing one on any particular glider. And the tiny handful of people who know that have no need of your testing offer.
Tensile tests like this are much more telling than just a material's failure or ultimate point.
Yeah, that five second transitional period between being full on and full off is both critical and poorly understood.
I'm a west coast foot launch guy...
Meaning you've never even heard of a hook-in check - let alone performed one.
...but I've got about 20 tows at enjoy field and whitewater combined.
- Do look into getting your shift key fixed.
- Meaning that:
-- you were using a "standard aerotow weak link" on the top end of a two point bridle limiting your towline tension to 226 pounds
-- if you ever find yourself in a Zack Marzec situation you and your magnificent testicles are gonna be just as fucked
- Enjoy Field, current home of Hang Glide Chicago - whose founder was killed along with his student by the failure of an illegally understrength front end weak link failure.
- Whitewater - where Roy Messing locked out and died on a piece of shit "release" from Lockout Mountain Flight Park with a long and well documented history of failure.
I've seen your guy's testing contraptions.
- Really? How many?
- How do they compare with the testing contraptions used by Wallaby, Quest...
http://ozreport.com/9.049
Weaklinks
Davis Straub - 2005/03/01
Steve Kroop, Bob Lane, and Rhett Radford decided to do a few quick and dirty tests just to see if a looped 130 lbs test line (IGFA DACRON TROLLING LINE) would hold 260 pounds with or without tying the loop so that the knot was "hidden."
We looped one end of a weaklink loop to the loop of a spectra bridle (part of a pro-tow and available here at Quest Air) and the other end to a loop of webbing approximately as thick as the loops that you would find on the shoulders of your harness. Tying the spectra to the hang gliding real life simulator outside the Quest Air and Flytec office entrance, Steve Kroop, and then Rhett Radford, slowly raised themselves up from a seated position by slowly pulling on the loop.
The weaklink broke before they were able to get their weigh off the ground. Steve and Rhett are quite a bit less than 200 pounds. The weaklink broke whether the knot was hidden or not.
Therefore I assume that the single loop of 130 lbs test line is providing a weaklink strength of about 1/2 G , about 120-150 pounds. Rhett remembers earlier tests which showed the strength of 135 lbs braided fishing line at 180-200 lbs. There is one additional strand on the end of the v-bridle at the Dragonfly side.
I assume that we don't want to have a stronger weaklink at the pilot side relative to the Dragonfly side. Still, given these results I think I'll test two loops and see if it can hold my weight. I assume that 1 G or so breaking would be enough to provide a reasonable margin of safety in the event that I came off the cart and plowed in.
I wonder just how strong the brick layer's line in Australia is supposed to be. They use four strands (to six strand for heavy pilots) in Australia of this line. I had always assumed that it was weaker than the line used in the US, just because they used more of it. Four stands were supposed to be at least 190 pounds, so it does seem to be weaker.
Follow up: Steve Kroop, Rhett Radford and I went out again and tested four strands of this line. Steve was able to lift his 185 lbs off the ground, and when I added a very small bit of tugging (slowly) on the line, it broke. Say 200 pounds. Four strands, still less than I G (300 pounds).
...Florida Ridge, Kitty Hawk, Lookout, Morningside, Cloud 9, Hang Glide Chicago, Whitewater, Cowboy Up...
- What are your recommendations for improving Tad's contraptions to the point at which they'll be capable of yielding meaningful results?
- It's actually only ONE contraption rigged in two different configurations for low and high ranges - as you might have deduced if you had actually bothered to read the captions.
http://www.flickr.com/photos/aerotowrelease/8317889807/
- In the low range - 0 to 388 pounds tension - the hydraulic cylinder sees the full load being applied to the item being tested.
- In the high range the cylinder sees only half the load being applied to the item so's I can measure up to 776 pounds.
I've also glossed over Tad's color ASCII text batshit insane manifesto.
I'm sorry, it seemed to me that you were making a disparaging remark about my "contraptions". And now you've moved on to talk about Tad's color ASCII text batshit insane manifesto without saying what was wrong with his contraptions.
But I got turned off when it was clear he doesn't know the difference between acceleration, mass, and what a forces are.
- Quote me something to back that statement - dickhead.
- And I get turned off when it's clear I'm getting attacked by some asshole who can't write a sentence that would make it through a third grade grammar class.
- OK, let's say I know ABSOLUTELY NOTHING about the difference between acceleration, mass, and what "a forces are". So what?
-- The FAA legal/safety range for weak links is 0.8 to 2.0 times the maximum certified operating weight of the glider.
-- I want to hit the center of that range - 1.4 Gs.
-- My glider maxes out at 319 pounds.
-- I want my towline tension limited to 446 pounds.
-- My two point bridle forms a sixty degree apex angle at the tow ring.
-- I want something at the top end of the bridle that blows at around 256 pounds.
So tell me what's wrong with that and why I - or anyone else - needs to know any more than that.
Maybe my machine can paint a better picture for the tow world.
- Oh, I'm ABSOLUTELY *POSITIVE* it will. It will UNDOUBTEDLY fill the void left by USHGA pulling all of the aerotow equipment specifications five days after Zack Marzec got snuffed by his Rooney Link.
- And I'm ABSOLUTELY *POSITIVE* Dr. Trisa Tilletti and all the other scumbags on the Towing Committee will welcome with open arms your data which proves their fourteen pages on 130 pound Greenspot in the 2012/06 issue of Hang Gliding to be the load of crap that it is - as those of us familiar with Dr. Trisa Tilletti had every confidence it would be upon reading the words: "HIGHER EDUCATION".
- So thirty-two years after Donnell's introduction of Skyting Theory there's still room for improvement in the tow world that can be brought about by Orion Price's load tester? What's wrong with things as they are now? What are ya gonna do next? Write some batshit manifesto about how everybody has everything wrong and they're getting bozos like Zack Marzec killed through their dumbfounding incompetence and stupidity?
Also in the background of that pic is a SEM...
Yeah, that was pretty obvious.
...it will be interesting to see the failure up close.
ABSOLUTELY FASCINATING! Fibers on the outsides of curves starting to blow microseconds before fibers on the insides of curves. If only Zack Marzec had known that he'd have had the warning he needed to pull in and avert the Rooney link pop!
Excellent article!!! Now the flight parks will be SO much more informed and accurate when they're pulling one-size-fits-all one and two point pieces of fishing line out of their asses.
Send them to:
OP C/O
SHGA
P.O. Box 922303
Sylmar, CA 91392
Also allow several weeks for processing. Label your links clearly.
- How ever will you manage to keep up with the work load?
- Let's say you find - after analysis with your ten kiloNewton load tester and scanning electron microscope - that a single loop of 130 pound Greenspot in the configuration in which Zack Marzec was using it when it blew up in his face has a breaking strength of 130 pounds.
-- Gonna make any recommendations?
-- What response do you think the aerotow industry will have?
- I notice you didn't have a single comment in any of the discussions on the Zack Marzec fatality last month. Is there any incident in the history of hang glider towing in which you believe other than optimum weak link strength may have been an issue relevant enough to merit one?
- Got any recommendations for G ratings for hang gliders? It's pretty fucking obvious you don't because you:
-- were quite content flying Rooney Links at Hang Glide Chicago and Whitewater
-- have never uttered a single syllable of criticism of Industry Standard Marzec Links
-- enjoy nothing more than pissing all over Tad's batshit manifestos pushing using sailplane protocols for towing hang gliders
Prediction...
By the end of next month the number of samples you'll have had mailed to you will be ZERO - and that figure will be a lot higher than any contribution to hang gliding that you and your fellow testosterone poisoned Sylmar dickheads are ever gonna make.
