Pulling the Zeppelin bend to 450 lbs! (video)

R

Ron

Location
Chattanooga
The video link is below; it just uploaded (11-May-2010 @ 8:00pm) so it's still being processed. AHHHH - the video is up as of 8:13pm. The quality may improve with further processing but it looks pretty good already.

Be sure you have sound on.

I wanted to test a Zeppelin under heavier loads than my weight, so I got out my scale and chain come-along and hooked it up. I wanted to see if the ZB was prone to slipping, creeping, and/or difficult to untie after heavy loading.

My scale only goes to 330 lbs, so I put it in one leg of a 2:1 with a ball bearing pulley to double its range. So when you see the scale in the video, the rope is experiencing double the scale reading.

I wanted a 440 lbs (200kg) load because that's the accepted rescue load. However, just because I took it to 450 lbs, doesn't qualify it for rescue by any means. But it sure builds one's confidence in the knot.

http://www.youtube.com/watch?v=Givv9cBB_Hw

I noticed the load weight slowly decreased with time, but I think it was a cummulative effect of nylon webbing, nylon prusik cords, and bunny knots settling. I could not tell that the ZB moved at all, but I want to re-run the experiment and measure the tails more carefully to see if there is any movement.

I load the knot to 450 lbs and although it isn't obvious in the video, I did let it set a while before releasing tension.

If you don't want to watch it all ~4.5 minutes, do watch the untie part to see if it unties easily after a 450 lb load.
 
Ron,

Nice work on the video, that is some skills.

Zeppelin bend has been my rope to rope bend for a few years now, it is reliable, and is always easy to break.

Thanks for putting some proof to it.

Northwind
 
Nice vid, Ron. And nice eye candy. How did you manage that PIP showing the spring scale? Separate camera?

Usually there isn't much to see when you apply tension to a knot, but there is one case where video would be very informative--watching a knot eat its tail under load. The first time you see it it is a real attention getter. Keep up the video work--its always fun to watch.
 
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i would like to see a drop test with various weights attached to a dynometer.

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So would I. Great video and narrative, Ron. I have used the ZB for truck pulls of logs and brush where it works well, but I have never shockloaded the ZB. If you stay within the safe working limits of the rope the Zeppelin bend, in pull applications, is very reliable.

Dave
 
Ive noticed on long ascents it can become tight and hard to take apart, but not impossible. it might have been my numb fingers on a cold day but it was definately tighter then when i started.
 
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Moray:...How did you manage that PIP showing the spring scale? Separate camera?...

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Yep! I had one on the scale and one on the knot. Because of movement, I was constantly 'chasing' the scale and knot until things settled down. I had some disappointment with my editor in that I couldn't rotate the PIP clip of the scale. I can the main track, but not a PIP track. I'll probably see if I can do that with Adobe Premiere if I have any free trial left.

But, I think I could have simulated the same thing with one camera. I'd set the camera on the scale and run up the tension. Then move the camera to the knot and repeat the pull. Then in my editor, I'd put one in the main track and one in a PIP track. Most probably couldn't tell the difference if the timing between the separate events was pretty close.

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marlinspiker:i would like to see a drop test with various weights attached to a dynometer.

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That would be interesting. Quite a complex test though depending on what one is really looking for. Drop tests almost demand a solid, rigid structure for the anchor. Drop tests are primarily used to test dynamic rope, but of course could be applied to static rope.

FWIW though, I'm not aware of data from any drop tests on arborist ropes or knots; so I wonder if we're expecting something from the ZB that we haven't considered with the knots we currently use???

Dave,
I sure am glad you posted that; that's the kind of info I was hoping would come up. Seems that the ZB is used more than we might have thought and is working very well.

Michael,
I'm sure any knot will tighten as it is worked - like long ascents. The climbing stroke imparts small but significant shock loads to a knot, then it's relaxed a bit, and then hit with the next stroke. All that tends to 'pack' the knot.

But, that loading would be no where near as heavy as 450 lbs. I pulled both Velocity and PMI 10mm rope to 450 lbs and you can see in the OP video how easy it was to untie.

I repeated the test with Velocity. The reason I haven't posted that test is when I did the untie part, I forgot to turn the camera on, but, the ZB in Velocity came apart just as easily as the PMI in the video.
 
I pulled one today with me (185#) and another guy (~160#) on a 5:1, to lift a tree off a roof. I feel certain we had nearly 2000# on it and lifted a 15"dbh red oak no problem.

I untied it with my hands in about a minute. It's a solid knot when you TDS it.
 
Something you guys are not doing is repetition of tension then slack. When footlocking or climbing srt of some fashion this would be very important to see how it reacts.

We know that the bowline works great in a pull test and can loosen up easily, but have come to the conclusion that its not good for a termination knot in a climbing system because of the tendency to come apart.

This should also be tested with the zeppelin bend. A straight pull does not show the true elements of what the knot will be exposed to when climbing.

Good tests so far, but lets keep pushing it farther to be more conclusive.
 
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I pulled one today with me (185#) and another guy (~160#) on a 5:1, to lift a tree off a roof. I feel certain we had nearly 2000# on it and lifted a 15"dbh red oak no problem.

I untied it with my hands in about a minute. It's a solid knot when you TDS it.

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Just out of curiousity, what kind of rope were you using?
 
I agree; I'm thinking we need to establish some static data first. If the knot weakens the rope too much, we may prefer not to use it and then the dynamic tests would not be of as much interest.

I'm about to do a pull to failure in a few moments, IF I can get the tensile machine to cooperate.
 
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