destructive testing

[opie]

OK folks, guys and gals...

I have done some de-structs today. Im going to upload the videos right now.

You all will be surprised where they failed and when.

[opie]

OK... The quality is what it is....Sorry.

The first one is 7/64 with a 6" bury on the fixed eye and stitched. 9" bury on the adjustable end.



It broke at 280psi. Total effective piston area is 11.78 cut in half since Im only using 1 cylinder on the machine. 1649 pounds.

And broke here..



In the fixed eye loop.

The second is configured the same other than a locked brummel on the fixed eye rather than stitching.



This one failed at 260 on the gauge, and in the exact same spot. The fixed eye loop. That comes to 1531 pounds.

I think its safe to say 7/64 is plenty strong.

[oldgringo]

When you said we would be surprised, that was my first thought. It is an obvious stress riser.

Thanks for your work!

[GrizzlyAdams]

Thanks opie! Waiting for rope to break in a video is almost as much fun as watching stoves in a video, waiting for water to boil

On reflection, one expects the rope to fail where it turns the sharpest corner, and while the posts involved here have non-trivial diameters (a) they still do provide the sharpest turn, and (b) I wonder if the flat edges on those posts aren't a contributing factor, providing a very focused point where two of those edges join.

Grizz

[opie]

And even after the slings broke, the adjustable loop functioned as if nothing had happened. There was some noticeable stress at the adjustable bury entrance and exit, but nothing that couldnt be milked back to normal, looking.

[opie]

Thanks opie! Waiting for rope to break in a video is almost as much fun as watching stoves in a video, waiting for water to boil

On reflection, one expects the rope to fail where it turns the sharpest corner, and while the posts involved here have non-trivial diameters (a) they still do provide the sharpest turn, and (b) I wonder if the flat edges on those posts aren't a contributing factor, providing a very focused point where two of those edges join.

Grizz

Yes.... That is what one of the guys there also suggested. That could be why they gave where they gave.

I think its a moot point as the slings broke at their limits for the rope itself. It would appear, that the slings I had suffered no derate.

I was expecting them to give at one of the buries... And alot sooner. I didnt think Id get past 120psi. You see the camera jump in the first vid... I wasnt even facing the machine for fear of not knowing where things were going to fly.

The second sling lost a few strands prior to breaking...

[oldgringo]

Thanks opie! Waiting for rope to break in a video is almost as much fun as watching stoves in a video, waiting for water to boil

On reflection, one expects the rope to fail where it turns the sharpest corner, and while the posts involved here have non-trivial diameters (a) they still do provide the sharpest turn, and (b) I wonder if the flat edges on those posts aren't a contributing factor, providing a very focused point where two of those edges join.

Grizz

I was wondering about dropping a piece of 2" pipe over each post, to see if that would alter the outcome.

[opie]

I was wondering about dropping a piece of 2" pipe over each post, to see if that would alter the outcome.

Well.. It may, and Im going to guess, that it would make a difference.

But Im happy with them breaking at the limits for a straight piece of rope.

And thats a $30,000 machine. Those posts are actually threaded nuts for clamping down HDPE pipe. They arent made to have the forces subjected to them that I did. Im not sure I want to re-create this testing. Not with that machine anyway. We have an older one I may be able to do something with.

[oldgringo]

Well.. It may, and Im going to guess, that it would make a difference.

But Im happy with them breaking at the limits for a straight piece of rope.

And thats a $30,000 machine. Those posts are actually threaded nuts for clamping down HDPE pipe. They arent made to have the forces subjected to them that I did. Im not sure I want to re-create this testing. Not with that machine anyway. We have an older one I may be able to do something with.

I understand, but this kind of Mythbusters monkey bidness is like eating Cheetos.

[warbonnetguy]

i'd still be interested to see what happens with a few knots, maybe a fig 8 loop and some others

i could tie some stuff up and send it to anybody who can do this kind of testing.