Gripping Hitches: A Proposed Rating System

[xarax]

I'm assuming the hitch has enough coils (efficiency) to prevent slippage along the pole. If the hitch slips on the pole, then coils must be added before you even get to talking about elongation.

 
   You haven't read anything I have written, have you ?  If you had, you would know that this is exactly THE issue - and there in no other issue !  How to transform the "generic" gripping hitch - with a given minimum number of coils - that will always slip along the pole under a certain loading, so that it will not slip along the same pole and under the same loading any more...That is why we compare different hitches, with the same minimum number of coils - because some will slip, and some will not, under the same load. When, under a certain load, two different hitches will not slip, we can not compare them - and there is no point to compare their elongation, or anything else, at this loading.
   If you think that the only solution to improve a hitch, is to put more coils, you can always use whatever hitch, try it under the load you use, and then just add more and more coils !  ( I would also suggest a small amount of glue.. )
   So, what you should do is ;
1. Fix the number of coils, the diameter of the pole and the diameter of the rope. (Of course, you should also measure your hitches with different values for those basic numbers.)
2. Tie the two or more hitches you want to compare/measure.
3. Measure their elongation under their maximum loading, that is, under the maximum load they can hold before they slip along the pole. If they will not slip under ANY load, you should reduce the number of coils, until the one slips and the other does not. Otherwise, you will discover that all hitches with 100 coils are equivalently magnificent, and will not slip before they break, indeed ! ( and I am talking about rope and/or pole breaking !  )
   

[knot4u]

I'm assuming the hitch has enough coils (efficiency) to prevent slippage along the pole. If the hitch slips on the pole, then coils must be added before you even get to talking about elongation.

 
   You haven't read anything I have written, have you ?  If you had, you would know that this is exactly THE issue - and there in no other issue !  How to transform the "generic" gripping hitch - with a given minimum number of coils - that will always slip along the pole under a certain loading, so that it will not slip along the same pole and under the same loading any more...That is why we compare different hitches, with the same minimum number of coils - because some will slip, and some will not, under the same load. When, under a certain load, two different hitches will not slip, we can not compare them - and there is no point to compare their elongation, or anything else, at this loading.
   If you think that the only solution to improve a hitch, is to put more coils, you can always use whatever hitch, try it under the load you use, and then just add more and more coils !  ( I would also suggest a small amount of glue.. )
   So, what you should do is ;
1. Fix the number of coils, the diameter of the pole and the diameter of the rope. (Of course, you should also measure your hitches with different values for those basic numbers.)
2. Tie the two or more hitches you want to compare/measure.
3. Measure their elongation under their maximum loading, that is, under the maximum load they can hold before they slip along the pole. If they will not slip under ANY load, you should reduce the number of coils, until the one slips and the other does not. Otherwise, you will discover that all hitches with 100 coils are equivalently magnificent, and will not slip before they break, indeed ! ( and I am talking about rope and/or pole breaking !  )
   

Well, that's your proposal for a rating system. My proposal is a bit different.

There is a factor called efficiency. You don't even get to go past that factor until you have enough coils for the hitch not to slip on the pole under any load. The efficiency may be higher (less coils) for some hitches, and lower (more coils) for other hitches. You figure out the efficiency, and then you move onto the next factor for the particular hitch, which is elongation.

Accordingly, some gripping hitches may have a high efficiency, but also a high elongation. Some coils may have a low efficiency but a low elongation. Some hitches may have a low efficiency and a high elongation. Some hitches may have a high efficiency, and a low elongation. I will generally give this type of hitch a higher overall rating, unless the complexity kills it.

Again, any gripping hitch that slips on the rope receives a ZERO (lowest possible rating). So, you either go back and change things (e.g., number of coils, pre-tightening, etc.), or you accept the zero for the particular application.

[xarax]

I'm assuming the hitch has enough coils to prevent slippage along the pole under any amount of load (i.e., rope will break before hitch slips on pole).

If you have found such a hitch - and you are satisfied with the !@#$%^&*() number of coils it needs to hold under ANY amount of load - then why bother ? Why do you want to measure things that they are perfect for their purpose ?

If the hitch slips on the pole, then coils must be added and tightened before you even get to talking about elongation.

   I was speaking about the tightening of the coils, not the addition of new ones ! We always suppose we measure and compare apples to apples, that is, gripping hitches with the same number of coils. So, if a hitch slips, you have to tighten the existing coils, as you say, and then load the hitch again, with the same load. If now it does not slip, and it is just at the upper limit of its ability to hold, THEN you measure the elongation.
   

[knot4u]

I'm assuming the hitch has enough coils to prevent slippage along the pole under any amount of load (i.e., rope will break before hitch slips on pole).

If you have found such a hitch - and you are satisfied with the !@#$%^&*() number of coils it needs under ANY ammount of load - then why bother ? Why you want to measure things that they are perfect for their purpose ?

Look. I'm not retired. So, I don't have time to go around in circles with you.

Imagine a gripping hitch that holds under any load, but it requires 100 coils to achieve that fete. That lowers efficiency and, thus, the overall rating of the hitch.

   I was speaking about the tightening the coils, not the addition of new ones ! We always suppose we measure and compare apples to apples, that is, gripping hitches with the same number of coils. So, if a hitch slips, you have to tighten the existing coils, as you say, and then load the hitch again, with the same load. If now it does not slip, and it is just at the upper limit of its ability to hold, THEN you measure the elongation.

Any slip means a ZERO overall rating for that hitch and that particular application.  The absolute rule of "no slippage allowed" is the apples-to-apples to comparison.  Then you make the efficiency, elongation, and simpleness the best you can under that absolute rule.

[xarax]

If the hitch slips regardless of the number of coils, then the hitch receives an overall rating of ZERO (i.e., lowest possible rating), and it goes straight to jail without passing Go.

Nooo...It goes straight to heavens, because it is a divine thing... There is no hitch that will slip "regardless of the number of coils". An interesting thing is to define the minimum number that any hitch needs to resist to a load capable of breaking the rope it is tied with. It would not  be such a big number some people might believe, even if we use the most slippery material and the most slippery pole.

I have not found there to be much difference in performance among friction hitches.

I have found there to be zero overall slippage with any legitimate friction hitch I've tested. So, there is nothing to compare there.

   If I were able to have such a wrong opinion about friction hitches, I would nt bother to measure anything on them, indeed...I would simply use whatever one of them, and just add more coils... And then my only concern would be how to find the hitch I would remember more easily. In this case, I would have put an image of this hitch on my cell phone - or make a tatoo...

[knot4u]

Nooo...It goes straight to heavens, because it is a divine thing... There is no hitch that will slip "regardless of the number of coils".

Cool, then the hitch does not receive an overall rating of zero.

It's called "theory". The concept of infinity is an example of theory. It's not something that is ever reached, but it's a real and necessary concept in mathematics.

[xarax]

There is a factor called efficiency. You don't even get to go past that factor until you have enough coils for the hitch not to slip on the pole under any load. The efficiency may be higher (less coils) for some hitches, and lower (more coils) for other hitches. You figure out the efficiency, and then you move onto the next factor for the particular hitch, which is elongation.

  I now understand your idea. You first find the minimum number of coils the particular hitch needs to resist to whatever load without any slippage, before the rope or pole breaks  - and only then you proceed to the next step. My idea is different. You first fix a number of coils, and then you measure the elongation of the particular hitch just before it starts to slip along the pole under a certain load. Now, if this hitch does not slip under any load, then you reduce the number of coils - until you find a smaller number, where a certain load can load the hitch to just the point before it will slip.- because what we are really searching for, is a hitch that holds using the minimum number of coils. With a hundred coils, any hitch will hold...I just do not see the point of measuring quantities of "perfect" hitches, that do not slip under any load....And I do not put a ZERO on any hitch that  will slip on a very high load, when it uses a minimum amount of coils.

[xarax]

Look. I'm not retired. So, I don't have time to go around in circles with you.

  I am retired, so I have less time than you to live, so my time is more valuable than yours. However, I do spend this time "to go around in circles with you"... Am I an idiot, too, I wonder...

Any slip means a ZERO overall rating for that hitch and that particular application.

  So, you are only interested in hitches that are useful to applications where any load - allowed for the specific rope material - will be expected and should be confronted, without any slippage....I do not think that most of the applications need such hitches...And if two hitches will hold under any load, what is the point of measuring their relative elongation? If they are perfect for this job - because you describe perfect hitches - you should only be interested in their simplicity, and nothing else.
   There is a broad range of hitches that use a small number of coils, that will slip under an extreme loading, but they are successfully used in every day applications, where this extreme loading is not expected. With modern materials, the ultimum breaking strength of ropes is very high - so when you are only interested in hitches that will not slip at all even in this high limit, you narrow the range of your hitches a lot - or you multiply the number of their coils a lot. 

The absolute rule of "no slippage allowed" is the apples-to-apples to comparison. 

To me, the absolute rule of "same number of coils" is the apples-to -pples comparison. However, I will follow your endeavor with much interest and attention - in my little left time...

[xarax]

There is no hitch that will slip "regardless of the number of coils".

The concept of infinity is an example of theory. It's not something that is ever reached, but it's a real and necessary concept in mathematics.

   I am not sure I understood your point here. However, if you mean that we will need an "infinite" number of coils to be sure that a whatever hitch will not slip, you have not read my next sentence ;  "It would not be such a big number some people might believe, even if we use the most slippery material and the most slippery pole."
   (There are no not-real concepts... So, what exactly a "real concept" does mean ?  )
 

[TMCD]

In all of this madness, you guys are basically arguing over how to perform the test. Xarax wants the test to be performed with a "fixed" number of coils and measure each hitch on how it performs based on that fixed number. Knot4U's testing is quite a bit different but actually still gets the job done IMO. His testing involves more and more wrapping until the hitch holds and he records his numbers then.

Both testing procedures have merit but I think Xarax's would probably be the one preferred in an actual testing facility. The reason is simple, it test ALL Hitches under the same guidelines and weeds out the weak from the strong...from the same starting point. That's all I'm saying and I'm not taking sides because as I stated, I think both procedures would yield interesting results.

[xarax]

   knot4u s idea has a merit : It produces a fixed number for each particular hitch. We can specify this number as such :
   Imagine a material A of, say, a 1/2' diameter,  and a pole B of, say, 8 or(and) 16 times the diameter of the rope. For the sake of a common standard, let us choose a stainless steel pole, with a surface as smooth as the surface of the  poles used for handles/grabrails in buses and trains...
  What is the number of coils any particular hitch will need, to hold, say, 50% of the load the rope itself can hold ? ( because it is not realistic to search the 100%, as any knot weakens the rope it is tied on). We suppose a lengthwise pull, parallel to the axis of the pole. We can also change the absolute and the relative dimensions of the rope and the pole, to cover more combinations.
   That "effectiveness" number could well be characteristic of any particular gripping hitch, and I believe it would be informative and useful ( as all objectively determined numbers are...)
   (Of course, when knot4u finds the one best hitch of the already well-known hitches that is characterized by the smallest such number, I will pop up and present him a pre-tensioned hitch that uses a much smaller number !  Because that was the idea behind the "pre-tensioning", right from the start : Reduce the number of coils, so we have the same result with fewer coils / a greater coil economy.)
   

[Hrungnir]

  What is the number of coils any particular hitch will need, to hold, say, 50% of the load the rope itself can hold ? ( because it is not realistic to search the 100%, as any knot weakens the rope it is tied on).

I hope you guys are going to use string or twine, because 12mm polypropylene or polyester can hold 2.100kg. Knots break at 40-80% of the rope breaking strength, so you are playing around with 1.050kg where the knot is expected to break.

[xarax]

you are playing around with 1.050kg where the knot is expected to break.

Yes, but that is not so great a force...we can use a car jack to reach it. ( A "high-lift jack", for example,  is a very useful tool for this). Otherwise, if we want a weaker load, we can go to 1/4". However, I personally am more interested in situations where a hitch would be used in outdoors and rescue operations, where the 1/2'  is a more commonly met diameter.

[knot4u]

The point of my proposal is to get data for each factor (efficiency, elongation, simpleness, and overall rating) for each hitch for a particular application and rope type. It's important to note the point is NOT to "weed out the weak from the strong". This proposal is in "Knotting Concepts & Explorations" because we're not knuckle dragging over here. We're standing upright on two feet, going in deeper, more technical, more precise.

You can't get the more precise data for each hitch if you fix the number of coils for a particular test. In that case, some hitches would fail. Some wouldn't. The ones that fail, that's too bad - no overall rating for those hitches because you set the testing at a fixed 4 coils for example. You would not know where the "breaking point" for that hitch is because you fixed the coils at 4. Freeze! Don't change the coils. They're fixed at 4 coils, oops.

Now, if you say, "Wait a second, let's slowly increase the coils for the failed hitches to see where they break," then we're talking about my proposal. Yes, my proposal is slower and more tedious, but it yields results that are more informative of performance.

[Sweeney]

The point of my proposal is to get data for each factor (efficiency, elongation, simpleness, and overall rating) for each hitch for a particular application and rope type.

The problem is that any given rope type, pole surface and pole diameter are at best difficult to reproduce. The starting precise data required is pole diameter, cross section measurements, coefficient of friction of the pole surface, rope diameter, construction and coefficient of friction of the rope - then start looking at various hitches and how they perform. Otherwise I really cannot see much point in this as a theoretical approach since any change in the principal inputs would render the result only valid for a situation which could not be accurately reproduced elsewhere.

Barry