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boku
Aug 2, 2007, 8:17 PM
Post #26 of 38
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Sure, send them to the PO box on the Contact page of the website in my Profile. I'll figure some way of making a test anchor stone.
Thanks, Bob K.
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majid_sabet
Aug 3, 2007, 12:38 AM
Post #28 of 38
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boku wrote: Sure, send them to the PO box on the Contact page of the website in my Profile. I'll figure some way of making a test anchor stone. Thanks, Bob K.
Bob
I need you to pull some prusik on static rope for me.
I can provide you with two Camera running at the same time .
Also pulling some knot from end to end like fig 8 vs. bowline on static lines.
let me know
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boku
Aug 3, 2007, 12:42 AM
Post #29 of 38
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majid_sabet wrote: Bob I need you to pull some prusik on static rope for me. I can provide you with two Camera running at the same time . Also pulling some knot from end to end like fig 8 vs. bowline on static lines. let me know
Sure, drop it in the mail. With a diagram. Don't forget the colored arrows. ;)
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domu888
Aug 3, 2007, 12:42 AM
Post #30 of 38
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majid_sabet wrote: domu888 wrote: Well, I can't supply the rock, but I could supply the bolt if you're interested. I'm not sure I can really post a suitable rock from Japan. Anyway, send me an address I can send the haken to and I'll see what I can do.  What you are showing on those photos looks like some hook out of bell helicopter or some military cargo hook. I do not think they are climbing related even if you got them off some camping web site.
Check out the forum post on them: do a search for "haken" and "Japan". I didn't buy them off a website, I bought them from a large chain outdoor store in Osaka, Japan. The forum post has more info, but suffice to say they are sold and used as climbing aids despite their obvious flaws.
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bigga
Aug 28, 2007, 11:30 AM
Post #31 of 38
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Hi, I saw you force meter 'break-o-tron' test. good going.
I've been looking in to getting a force gauge and test stand, but they are soo expensive. Force gauges are at least 600$ (at least for the loads I am thinking of) of the stands go for at least four times that price.
I was interested to find out if you built it yourself and what did that involve. And if not, in any case, do you know why they are so expensive?
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slacklinejoe
Aug 29, 2007, 10:33 PM
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I'm working on a project that could certainly use your testing equipment. I've been working on different strengths for webbing wear in different patterns. I'd be glad to provide any webbing samples you might need. I could certain reimburse you for your time and / or build you something out of webbing for your testing process.
Webbing wear project
(This post was edited by slacklinejoe on Aug 29, 2007, 10:33 PM)
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boku
Aug 29, 2007, 10:58 PM
Post #33 of 38
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bigga wrote: Hi, I saw you force meter 'break-o-tron' test. good going. I've been looking in to getting a force gauge and test stand, but they are soo expensive. Force gauges are at least 600$ (at least for the loads I am thinking of) of the stands go for at least four times that price. I was interested to find out if you built it yourself and what did that involve. And if not, in any case, do you know why they are so expensive?
Bigga,
I believe that the reason that most multi-ton force measurement devices are so expensive is that they are designed for uses that require high precision and high reliability. When you are doing three-sigma testing on expensive parts, every corrupted test means destroying another expensive unit, and high precision is required to capture the nuances of strain, elongation, and failure.
As opposed to a guy like me who is testing cheap junk and doesn't care much about precision beyond three digits...
Anyhow, yes, the Break-O-Tron is a combination of homemade parts and off-the-shelf stuff from Harbor Freight:
* The heart of the Break-O-Tron is this 10-ton pullback ram from Harbor Freight:
http://www.harborfreight.com/...taf?Itemnumber=33611
* Hydraulic pressure to apply force at the ram comes from the hydraulic pump in this Harbor Freight porto-power kit:
http://www.harborfreight.com/...taf?Itemnumber=44899
* The chassis of the device was MIG welded up from a bunch of scrap tubing I had left over after cutting up an abandoned engine hoist. These Web pages have some photos of earlier incarnations:
http://www.hpaircraft.com/...pdate_8_april_07.htm
http://www.hpaircraft.com/.../update_7_may_07.htm
* Pressure measurement is done with the McMaster-Carr part# 3708K516 0-7500 PSI hydraulic pressure gage with +/- 1% full scale accuracy:
http://www.mcmaster.com/...nter.asp?pagenum=556
* Force Measurement is done by simply multiplying the hydraulic pressure by the piston area. After buying the pullback ram, I disassembled it and measured the piston diameter D and piston rod diameter d, used pi*r^2 to calculate their areas A and a, and subtracted the rod diameter from the piston area to arrive at the effective piston area. For the one I bought, the areas were A=2.466in^2 and a=1.313, yielding an effective area of 1.153in^2. So when doing a test I either observe the hydraulic pressure at failure and multiply it by 1.153 to get the force, or take the desired force and divide it by 1.153 to get the target test pressure. Hokey? Yup. But it works well enough.
* One of the downsides of the Break-O-Tron is that the pullback ram only has about 5" of travel. So when you're testing nylon slings to failure, you often bottom out the ram before the sling breaks. However, you can also use the ram as a tension scale by filling it with hydraulic fluid and then screwing the pressure gage directly into the hydraulic port. You have to apply the force using some other means (such as a winch or a come-along), but the pressure shown on the gage is directly related to the force being applied to the ram unit.
I hope that helps. Let me know if you have any other questions.
Thanks, Bob "BoKu" K.
(This post was edited by boku on Aug 29, 2007, 11:19 PM)
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boku
Aug 29, 2007, 11:15 PM
Post #34 of 38
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slacklinejoe wrote: I'm working on a project that could certainly use your testing equipment. I've been working on different strengths for webbing wear in different patterns. I'd be glad to provide any webbing samples you might need. I could certain reimburse you for your time and / or build you something out of webbing for your testing process. Webbing wear project
As I explain in the previous post, the Break-O-Tron is not ideal for testing pieces of webbing more than about 4" long (that is, 8" in circumference). Much more than that and the webbing stretches so much that the ram bottoms out before the webbing breaks.
Testing webbing is also troublesome because the knots that secure it in a loop or to the tension hooks are weak points that might break first. Also, it's usually easiest to test a loop of webbing, but that's a bit problematic because the loop taken as a whole is about twice as strong as a single strand - that's because the loop is composed of two strands. What I'll usually do is either treat the loop as a whole and say it has a breaking strength of X, or just say that the webbing has a strength of x/2. However, that really only valid (and even then not entirely valid) if the webbing does not break at the knot.
And of course, the tests I do are probably +/- 2% accuracte at best. That's enough for a lot of purposes, and perfectly good when comparing two test conditions, but is a lot less accurate than you'd get with good professional equipment.
Given all that, I'd be glad to test some webbing samples for you. Your best bet is to make it easy on my by pre-tying them, with well-dressed water knots, in 4" loops in which the damaged area is exactly opposite the knot. All of the test loops should have the same length to reduce setup changes between tests. Please identify each test article either by number or with a description.
Send them to the PO box on the Contact page on my Web site:
http://www.hpaircraft.com/contact/
Thanks, Bob "BoKu" K.
(This post was edited by boku on Aug 29, 2007, 11:19 PM)
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slacklinejoe
Aug 29, 2007, 11:21 PM
Post #35 of 38
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Thanks Bob. Actually I plan on sewing this webbing so there won't be knots for weak spots.
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boku
Aug 29, 2007, 11:37 PM
Post #36 of 38
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slacklinejoe wrote: Thanks Bob. Actually I plan on sewing this webbing so there won't be knots for weak spots.
Good, that'll be much better than knots.
If you can, sew an eye at each end with about 3" of webbing between them with the bad spot centered in that 3". That will yield a test piece that's pretty long, but since there's only about 3" of undoubled webbing the stretch won't be so bad. That will give better test results than a loop, since it won't be corrupted by having different elongations on the doubled side with the bar tacks and the single-ply side with the bad spot.
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sixleggedinsect
Sep 2, 2007, 5:44 AM
Post #37 of 38
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majid_sabet wrote: I need you to pull some prusik on static rope for me. I can provide you with two Camera running at the same time .
i would be pretty surprised if you could make nylon prussiks break with 4-5" of travel. the thin stuff stretches like crazy before it goes, so you might not find out whether the prussik would melt, or break, or slip, or strip sheath, before the BOT stops hauling. plus, majid, arent you more interested in drop testing than slow pull stuff?
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thomasribiere
Sep 9, 2007, 8:57 AM
Post #38 of 38
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Registered: Aug 24, 2002
Posts: 9306
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Interesting, but :
Have you tested only one biner?
The machine is not calibrated.
The force is slowly increasing which doesn't really match the climbing reality.
But still interesting.
And watch yourself, the machine seems heavy!
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