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Isc rope grab help


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57 minutes ago, Pete Mctree said:

What diameter range did the manufacturer specify for your grab - never seen one that maxed out at 11mm before …. 

The makers state 9 to 13mm.. Thing was though, it just did not feel right.. I think what the issue is, the maximum diameter may very well be 13mm ROPE, as this is squashy, so the grab has no problem grabbing. Indeed, my climbing rope is 13mm and it will grab that no problem at all.

 

Now, when i tried it on a steel core flipline of 11mm, [i think it actually measures a bit more] it worked fine, but did not feel "happy" shall we say.. It was certainly much happier on my 11mm [or thereabouts] squashy rope lanyard.

 

I think the difference is that the flipline is hard and incompressable so the grab cannot get such a firm grip.

 

Think of it like this; If you dangled a half inch diameter rope vertically down from a beam and grabbed it with your hands, you might well be able to hold your own weight. If you swapped the rope for a smooth half inch steel bar [or indeed a wire rope] and tried again, you would have no chance..

 

Do not misunderstand, it worked ok on the 11mm flipline, but if i went up to 13mm, i have an idea things might not have been too good at all.

 

I swapped it for a Prusik.. It works really well, but it is a bugger to adjust. If i was doing it all day every day like you lot, it would be tempting to go back to the rope grab as the Prusik is hard work.. But for me, although a pain, at least i know for a fact that no matter how much a flap the flipline about, when i go to lean back i will not fall off the tree!!

 

john..

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11 hours ago, john87 said:

The makers state 9 to 13mm.. Thing was though, it just did not feel right.. I think what the issue is, the maximum diameter may very well be 13mm ROPE, as this is squashy, so the grab has no problem grabbing. Indeed, my climbing rope is 13mm and it will grab that no problem at all.

 

Now, when i tried it on a steel core flipline of 11mm, [i think it actually measures a bit more] it worked fine, but did not feel "happy" shall we say.. It was certainly much happier on my 11mm [or thereabouts] squashy rope lanyard.

 

I think the difference is that the flipline is hard and incompressable so the grab cannot get such a firm grip.

 

Think of it like this; If you dangled a half inch diameter rope vertically down from a beam and grabbed it with your hands, you might well be able to hold your own weight. If you swapped the rope for a smooth half inch steel bar [or indeed a wire rope] and tried again, you would have no chance..

 

Do not misunderstand, it worked ok on the 11mm flipline, but if i went up to 13mm, i have an idea things might not have been too good at all.

 

I swapped it for a Prusik.. It works really well, but it is a bugger to adjust. If i was doing it all day every day like you lot, it would be tempting to go back to the rope grab as the Prusik is hard work.. But for me, although a pain, at least i know for a fact that no matter how much a flap the flipline about, when i go to lean back i will not fall off the tree!!

 

john..

So, when using the 13mm wirecore did it ever slip or creep after it had grabbed whilst still weighted ?

 

Do you understand that the cam grabs on the sheath and does not rely on any major deformation of the core? And that a significant amount of the friction is from the cam pressing the line against the body of the device?

This means that a thicker line will have more grab/friction as opposed to a skinny 11mm one….. You follow?

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34 minutes ago, Pete Mctree said:

This means that a thicker line will have more grab/friction as opposed to a skinny 11mm one….. You follow?

I do not think he does actually, adamant that the cam is the only source of friction.

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36 minutes ago, Pete Mctree said:

So, when using the 13mm wirecore did it ever slip or creep after it had grabbed whilst still weighted ?

 

Do you understand that the cam grabs on the sheath and does not rely on any major deformation of the core? And that a significant amount of the friction is from the cam pressing the line against the body of the device?

This means that a thicker line will have more grab/friction as opposed to a skinny 11mm one….. You follow?

Don't bother Pete, he's just scared of his climbing kit and making up rubbish to justify it. 

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1 hour ago, Pete Mctree said:

So, when using the 13mm wirecore did it ever slip or creep after it had grabbed whilst still weighted ?

 

Do you understand that the cam grabs on the sheath and does not rely on any major deformation of the core? And that a significant amount of the friction is from the cam pressing the line against the body of the device?

This means that a thicker line will have more grab/friction as opposed to a skinny 11mm one….. You follow?

I never used as 13mm wire core, just an 11mm one, and that felt borderline to be honest..

 

Now, you mention friction and that a "significant amount" comes from the line being pressed against the body of the thing.

 

Now, i see what you are getting at, but problem is, this is against the laws of physics..

 

Friction, is independant of area.. what i mean is, if you had a rectangular body of say 10lbs in weight and you tried to drag it along. It would make no difference as to whether it was resting on its edge, or end, or flat side, as to how much friction there was, so that is not the answer..

 

The cam obviously contacts the sheath, but also squashes it in, the same as if you squeezed it between your fingers, thus obtaining more "grab" as it were, same as you could pull on a rope harder than you could a steel rod..

 

john..

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