Author Topic: A simpler TackleClamp hitch.  (Read 26621 times)

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: A simpler TackleClamp hitch.
« Reply #15 on: November 10, 2012, 01:24:14 AM »
   When, after a long journey in the KnotLand, I arrive at something that catches my eye and makes my heart beat faster, I can not help but ask myself : What would Ashley have said about it ?
   There is no need for any overhand knot at the end of the line, as I thought at Replies #8 and #9 of this thread... (1),(2). Just a simple U-turn underneath the two round turns, a strong pull of the standing end against the pole, and the hitch is locked in the same way and degree as it did at the hitches presented there.
   And which hitch is this ? Holy Cow ! It is the Cow hitch. :)  I have not seen this most simple and secure addition/lock to the humble Cow hitch, which transforms it to a Bull ! ( Unfortunatelly, the name "Bull hitch" is taken, by something much weaker than the hitch presented here. The fact that the Bull hitch can not be pre-tension-ed as hard as the hitch presented here, is a direct consequence of the fact that the opposed bights lock is stronger than the lock achieved by a double nipping loop. ) Why nobody told me about this hitch, I do not know.
   The interested reader can read the previous posts of this thread, and follow the reasoning that brought us here. The "locked Cow hitch" is much simpler than the Tom Foul s hitch (3), much easier to tie and inspect, probably simpler even from the beautiful Andalusian hitch presented recently (4). I believe that is a fine, almost perfect solution for the not-easy problem of a 2-wraps pre-tension-able hitch, able to withstand lengthwise pull.

1. http://igkt.net/sm/index.php?topic=4035.msg24356#msg24356
2. http://igkt.net/sm/index.php?topic=4035.msg24357#msg24357
3. http://igkt.net/sm/index.php?topic=3197.msg19074#msg19074
    http://igkt.net/sm/index.php?topic=3197.msg19224#msg19224
4. http://igkt.net/sm/index.php?topic=4069.0
« Last Edit: November 10, 2012, 02:39:33 AM by X1 »

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: A simpler TackleClamp hitch.
« Reply #16 on: November 10, 2012, 12:13:54 PM »
  As it happens in the case of the TackleClamp hitch (1) and all those extremely tight pre-tension-able hitches, it may be difficult to untie it after it has been tightened hard, by pulling the standing end against the pole. ( I often use my hands and my feet, at the same time, like a rower  :), and I obtain a very tight grip, a difficult to release hitch, and a pain in the back...) So, it may be better to tie it in its slipped form in the first place, so it can be released easily by pulling the "trigger", and dis-placing the local paths of the segments of the rope which keep the mechanism loaded and locked.
  See the attached pictures for two slightly different versions of the slipped locked Cow hitch. At the second ( the B ), the tail passes underneath itself, deeper into the space between the pole and the nub of the knot. This way it raises the bulk of the knot a litle bid, something that may be beneficial for the locking mechanism - because the locking bight meets now the standing end at a less obtuse angle- closer to the optimum right angle. However, all those depend upon the relative dimensions of the pole and the rope, and the friction coefficients of their surfaces. So the user should try both versions with the materials at hand, and judge which one is better suited to them.

P.S. I would never had imagined that we could ever discover a 2-wrap hitch that is tighter even from the Constrictor... How many other things are still there, just under our nose, waiting for us to reveal them ? 

1. http://igkt.net/sm/index.php?topic=3813.msg24500#msg24500

SS369

  • Global Moderator
  • Sr. Member
  • *****
  • Posts: 1788
Re: A simpler TackleClamp hitch.
« Reply #17 on: November 11, 2012, 01:13:13 AM »
I am finding that this "locked" cow hitch stays set better than the Pedigree Cow hitch and is a bit harder to untie after an approx. 200 lbs load. (Not the slipped-untested version) This may be due to the  particular rope construction I used.
Though, I have not found either of them provides a good resistance to lengthwise pulling on a smooth pole.

SS

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: A simpler TackleClamp hitch.
« Reply #18 on: November 11, 2012, 04:00:53 PM »
  Thank you SS369 - it is good that there are some members of the Forum that are not airborne all the time ! :)

  It would be interesting to compare the Pedigree Cow hitch with the locked Cow hitch. I argue that, although they might look similar, they belong to two different worlds, far apart the one from the other !  :)
  I do not believe that any of those two hitches have a problem with "security", i.e. slippage. However, the locked Cow hitch can be pre-tensioned, can accumulate any tension forces that are stored in it ( in its two turns) however strong they might be, while the Pedigree Cow hitch can not. A pre-tension-able and pre-tensioned hirtch can withstand a lengthwise pull much better than a simply tied and tightened one. To see the difference, it is better if you use nylon ropes, which can be elongated much more that the other materials. A slight slippage of the locking mechanism would release the grip on a non-nylon rope, but it would not make much difference on a nylon rope.
  The Pedigree Cow hitch works just like all the common hitches, by squeezing the tail underneath a riding turn. No relation whatsoever with the locked Cow hitch. In the later, the working end is locked in place by the opposing bights mechanism - where, in the place of the second bight, we use the U-turn of the continuation of the tail. The squeezing of the tail itself plays but a minor, secondary role. If we could measure it, we would see that there are almost no tension forces arriving all way to the tail - most of them have been nipped already in the intersection of the standing end with the two rims of the two opposed bights.
   One has to be careful to load this hitch in the proper longitudinal - related to the axis of the pole - orientation, so that the locking mechanism is not distorted - so, in the one way, not the other ! ( it is a highly asymetric hitch, despite the appearances...). On the contrary, it makes no difference how you are going to load the Pedigree Cow hitch, because the tail is nipped there by its position between the rope and the surface of the pole, not between the various segments of the rope itself, as it happens in the case of the locked Cow hitch.
   We can not expect anything better from ANY two wraps hitch, I believe. I have tested the most tight 2-wrap hitches we have, the Strangle and the Constrictor, and I have seen that the locked Cow hitch :
1. can be tightened much more ( because it can be tightened by pulling the end against the pole, perpendicularly to the axis of the pole, so we can apply a much greater hand and feet force ),
2. its two turns are tensioned at the same time, so the elognation of the tighten segment is greater,
3. it keeps the tension that is inserted and stored into it as well as the Constrictor- its standing end does not slip even one mm
4. the direction of the loaded standing end alongside the pole does not distort the shape of the knot, as it does in the cases of the Strange or the Constrictor.
  If you want more gripping power, you should rely on the 4-wraps Double Cow hitch presented at the start of this thread - I guess that a double Cow hitch can store twice as much energy as a locked (single) Cow hitch can, so grip the pole with twice as much force. I would nt use the locked Cow hitch to withstand a heavy lengthwise pull on a slippery pole, of course. We have the marvel of the original TackleClamp hitch for this purpose, or the lighter, but also very tight, Double Cow hitch - provided we hang the load from both their ends.
   I have also tied the locked (single) Cow hitch with more that two turns. It seems that 3 ( at the one-and-a-half locked Cow hitch)(or even 4 ?) wraps make some difference, but after that we can not tension the turns as much as we wish, because of the friction on the surface of the pole and the reverse capstan effect.

   P.S. I have noticed the quotation marks on the "locked" :). I do not give much attention to names, and I do not have the feeling of this unknown to me language that would allow a proper selection... I though that " lockable" would, perhaps, be more correct - but I had no other, better idea. I would appreciate any suggestion, because I am afraid we have to name things, even if they are tangles of ropes , i.e. pure shapes... They have become too many !  :)
« Last Edit: November 11, 2012, 04:07:29 PM by X1 »

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: A simpler TackleClamp hitch.
« Reply #19 on: November 11, 2012, 04:29:05 PM »
   There is another test one can perform, to see how tight a locking mechanism is. Instead of pulling the standing end, drive the knot to iits limits, and see how well the lock behaves at those limits, make the opposite/reverse : Push the standing end of a locked knot, to see if it will obey to your action, or not !  :)
   I have tied the locked Cow hitch, and the Pedigree Cow hitch, on the same slippery pole and with the same slippery rope, and tensioned them with the same force ( same hands and feet !  :)). I have seen that the locked Cow hitch will not give to a push of the standing end, while the Pedigree Cow hitch was much more willing ! That is an indication ( not a proof...), that the local forces that act on the standing end of the locked Cow hitch are stronger and more efficiently applied in order to prevent its displacement, than those of the Pedigree Cow hitch.   
« Last Edit: November 11, 2012, 04:30:24 PM by X1 »

kd8eeh

  • Exp. Member
  • ****
  • Posts: 159
Re: A simpler TackleClamp hitch.
« Reply #20 on: November 11, 2012, 08:52:27 PM »
looking at the locked cow hitch, at first i was under the impresion it was a modified munter hitch.  i began experimenting and found another working tackle clamp hitch based on a zigzag knot.  what you do is tie a zigzag knot, but every other time the rope comes around, pull the initial line back to the pole, and continue a few times.  then secure the end as desired.  slipping it underneath as in the locked cow hitch seems to be ideal, but not necesary.  then it may be easily tightened, and will not loosen easily because it  has to go through these segments.  the only problem with it is it will tighten the middle strand incredibly tight, but the other strands get progressively looser as you go out.  still, the middle line can have an incredible amount of tension.  perhaps this is not the most useful tackle clamp hitch, but it is food for thought.  i don't really have a good pole to tie it on, but you can see the point

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: A simpler TackleClamp hitch.
« Reply #21 on: November 11, 2012, 10:30:27 PM »
looking at the locked cow hitch, at first i was under the impression it was a modified munter hitch.

  Yes, It can be seen as such - or as a "down under"  :) Pedigree Cow hitch ( ABoK#1683), as mentioned by SS369.    However, I examine the lock, not the looks - how the standing end is locked after it has been tightened as much as possible - so the tensile forces accumulated within the round turns remain in action, and help the hitch to better withstand lengthwise pull when it will later be loaded accordingly. Notice that I am talking about the mechanism of the lock of the Standing end, not of the tail - which is a much easier to achieve (with hitches tied on hard surfaces ), minor issue.
   If you read the thread from the start, you will see that my staring line was the TackleClamp hitch, not the Cow hitch. It was only later that I thought to utilize the apparent resemblance with the Cow hitch, to help the user visualize and remember all those hitches. The Cow hitch, in general, has only one bight, and the Pedigree Cow hitch, in particular, does not use the U-turn of the tail to secure the Standing end, but the tail itself. In the locked Cow hitch, the U-turn locks the Standing end, so it will not slip and release whatever tensile forces have been accumulated within it during the pre-tensioning phase.
   Lock the Standing end, that is the purpose of any pre-tensionable hitch that is intendebed to remain tensioned, when it will be loaded by a lengthwise pull. The lock of the tail itself is an easy task, and we have dozens of other hitches that achieve this in a most secure way. We have to lock the Standing end AND the tail in the same time, in order to store the energy we will later need/use, inside the multiple wraps, to withstand a lenghtwise pull.

 
what you do is tie a zigzag knot, but every other time the rope comes around, pull the initial line back to the pole, and continue a few times.

   If you continue TWO times, you have the TackleClamp hitch... :) It could well be named "ZigZag hitch", but perhaps the person who named it had not thought of this adjective... :)

  the only problem with it is that it tightens the middle strand incredibly tight, but the other strands get progressively looser as you go out.

  Why are you saying this ? It would be like the shoelaces of shoes, I suppose : All bights will eventually be tightened at the same degree, because the segment(s) of the rope that penetrate(s) them will slip through them, and the tension forces would eventually be equalized. I have not tested this, I only make a guess...
  Perhaps you can do a relevant experiment by yourself, and try to "measure", in a way, the tensile forces in each segment - by evaluating the individual resistance of each one in a perpendicular pull.


kd8eeh

  • Exp. Member
  • ****
  • Posts: 159
Re: A simpler TackleClamp hitch.
« Reply #22 on: November 12, 2012, 04:10:33 AM »
so, firstly, i was under the impression that a tackle clamp hitch is family of hitches that hold tension around an object, like a constrictor knot, or many of these others.  secondly, i read the term zigzag knot in abok, although i don't remember the number.  thirdly, the tension in each string is different, because each string is separated form the loaded end by yet another turn, a caracteristic that i am generally very fond of about a zigzag hitch/knot, because it makes it so that even after an extremely heavy load the end is loose, esentially it is another type of tensionless hitch.  i have tested the tightness of each loop by trying to slide it up and down, and i have conclusively proved in multiple types of rope that this is tightened irregularly.  also, from what i looked at, i found that these hitches tend to have a loop component that is then pulled closer to the origin as the knot is tightened, or at least the more elaborate ones do.  this knot has that property, really on multiple levels, and then to lock the loaded stand i used the bends induced by the bends that pull the rope in a bumpy path.  i do see how your locking mechanism seems to work, and this knot can be locked in the same manner, should you choose to.  however, what i really like about it is how easy it is to untie. 
on a less related topic, i do think that zigzag knots are widely underused, seems how they are the only tensionlesss hitch, to my knowledge, that is only dependent of fricton between the rope and itself.  here it is secured with a clove hitch around my finger.  although i tied it with many wraps here, it generaly has almost no tension left after only two wraps. 
on an even less related note, can someone please explain how to quote other people?  i can't tell how to, and it makes these look so nice.

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: A simpler TackleClamp hitch.
« Reply #23 on: November 12, 2012, 02:35:06 PM »
i was under the impression that a tackle clamp hitch is family of hitches that hold tension around an object, like a constrictor knot, or many of these others.

   Please, stay under this impression !  :)
   However, this "many" is not sooo many - better, it is not many at all ! What else do you have in mind, except the Constrictor ? ( Which can not be tensioned as hard as those hitches, because its ends can not be pulled against the pole - and, of course, it does not makes use of a mechanical advantage, as the TackleClamp hitch does.)

the tension in each string is different, because each string is separated from the loaded end by yet another turn

   If that is so, yes, you are right. I had not realized you were meaning this. ( Your new photos, although focused neither on the knot, nor on the knot-tyer  :), are telling ).If the connecting segment(s) between a first opposing bight and a second one, makes a whole turn around the pole before it goes through the second one, the tensions would not equalize very easily. However, this round turn would absorb a great deal of the connecting energy ( reverse capstan effect ), so any pull on the first bight would not pull the second bight very easily...
   Could you, please, make some rough sketch or take some clear pictures that will illustrate what you say ?
   Have a look at the hitches shown at (1) and (2). Can can consider the " ZigZag hitch" you show, as a multiple, super-imposed U-hitches, like the ones shown there ?

even after an extremely heavy load the end is loose.

   As I have tried to explain in my previous reply, the TackleClamp hitch is not answering in the problem of securing the tail, but the problem of securing the Standing part. It is very easy to secure the tail - any hitch worth its salt does it ! It is a completely different thing to secure the standing end, so any tension that has been accumulated within the round turns during a pre-tensioning phase will remain in place, even after the standing end is not loaded any more. 


i have conclusively proved

  Unfotunately, we can not "prove" something about knots without repeated, detailed laboratory experiments, with instruments, measurements, etc. We can have indications, but not "proofs"- conclusive or not.

although I tied it with many wraps here, it generally has almost no tension left after only two wraps. 

  That is why we use 2-wrap hitches most of the time, and we seldom need 3 or more wraps. It is due to the capstan effect. However, to tie a hitch that would be able to withstand a lengthwise pull, we need more wraps. I have seen that this is achieved easier, if, before we apply the load, the hitch is already pre-tensioned, so those multiple wraps would not take an elliptical form when the hitch will be pulled from its one side, alongside the axis of the pole. That is what the original TackleClamp hitch does, and what the various lighter versions of it do, albeit in a lesser degree. The pre-tensioning benefit is more pronounced if we tie those hitches on nylon, because nylon can be stretched / elongated a lot, and many times, without losing its strength ( without fatigue).

1. http://igkt.net/sm/index.php?topic=3104.msg18513#msg18513
2. http://igkt.net/sm/index.php?topic=3104.msg18514#msg18514
« Last Edit: November 12, 2012, 03:10:05 PM by X1 »

kd8eeh

  • Exp. Member
  • ****
  • Posts: 159
Re: A simpler TackleClamp hitch.
« Reply #24 on: November 13, 2012, 04:32:41 AM »
so, i tried to take better pictures of a zigzag hitch.  a zigzag hitch is a way of multiplying a munter hitch, which is the simplest zigzag hitch.  then, your come around the loaded end and go back around the other direction, like the first step in tying a munter hitch (assuming you actually tie the munter hitch around something, not just to wrap around a carribeaner) .  repeat, and you have a zigzag hitch.  it is a great tensionless hitch, because eatch wrap exponetially reduces tension, instead of linearly as in a normal tensionless hitch.  also, if you look at the zigzag tackleclamp hitch, i basically said to secure the end with any hitch worth its salt.  the hitch does secure the standing part, by pushing it between segments going closer and then leaving the pole. 
as far as super imposed u hitches, i think yes, but i have never heard of a u hitch, although i can guess it seems to be that.  personally, i don't see why this hitch isn't more used.  it is incredibly strong with respect to perpendicular pull, and is extremely easy to untie.  also, it will tie securely on surfaces with essentialy no friction. 
as far as use of the zigzag tackleclamp for lengthwise pull, i do not think it would be exceptionally secure, because only the middle strand is really tight.

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: A simpler TackleClamp hitch.
« Reply #25 on: November 13, 2012, 06:55:03 AM »
a zigzag hitch is a way of multiplying a munter hitch, which is the simplest zigzag hitch.


   Very good description ! So, in a ZigZag hitch the working end forms/passes through only one bight each time, and then it makes a round turn, forms/passes through another bight, etc. It is a kind of weaving the working end(s).
   It is better if you show it with 2 or three bights ( not many), because the many-wraps ZigZag hitch looks like a messy tangle of ropes. Also, I think it would be easier for you if you place the knot on a horizontal surface, so you can focus on it. If you hold the knot in mid-air, without even looking through the lens or the viewfinder, it is difficult to focus on anything...

 
« Last Edit: November 13, 2012, 06:57:40 AM by X1 »

kd8eeh

  • Exp. Member
  • ****
  • Posts: 159
Re: A simpler TackleClamp hitch.
« Reply #26 on: November 13, 2012, 10:47:34 PM »
i'm using my laptop's webcam, not a camera, so the picture is tied in midair at the hieght of the webcam.  i can see it fine, but when i let it get into good focus, the file output is often over 100 kb and i have to try again.  but overall, yes, that is exactly what a zigzag hitch is.  i would think it would be much more commonplace.

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
Re: A simpler TackleClamp hitch.
« Reply #27 on: November 13, 2012, 11:38:46 PM »
   Dowload GIMP 2.8
   http://www.gimp.org/
   After you open a file, export it in a smaller file, less than 100 KB.

« Last Edit: November 14, 2012, 01:37:34 AM by X1 »

X1

  • Inactive
  • Sr. Member
  • *
  • Posts: 1200
6-wrap Double Cow hitch
« Reply #28 on: December 03, 2012, 04:34:37 AM »
  When we compare hitches designed to withstand a lengthwise pull, we should always compare hitches with the same number of round turns - because we have seen that, in such hitches, one more round turn can make a big difference. In the case of pre-tensionable hitches, like the hitches presented at this thread, this effect is ever greater, because one or more additional round turns are able to be elongated more, and accumulate and store a much greater amount of tensile forces - so, when an already tightened ( by a pull of its standing end(s) against the pole ) hitch, with a larger number of wraps, will confront a subsequent lengthwise pull, it will be able to withstand this pull much more efficiently than a similar hitch with a smaller number of wraps. Of course, this effect will not continue ad infinitum, as, beyond a certain number of wraps, it is difficult to tighten the hitch pulling the one, or even both the ends of its multi-wraps coil. I do not know which is the optimum number, and I suppose that it will depend on the friction coefficients of the rope and the pole, but, with the slippery poles and ropes I use, it is at least 6, and perhaps even 8.
   Now, one may ask : Why is this so ? If the total friction forces are independent of the apparent area of contact ( Amontons second law of friction), the number of wraps should make no difference. Yet it does, as one can easily verify by himself, if he compares the 4-wrap Double Cow hitch with the 6-wrap same hitch, shown at the attached pictures. And which is the optimum number of wraps ? I wish I knew, and I will say that a theoretical model of hitches has some relation to the physical reality of practical knots, only if it will be able to address those simple questions. Otherwise, one can always figure out ( fabricate ) an equation coming out of the blue, with a sufficiently large number of freely adjustable coefficients, and, by trial and error, succeed in selecting the best-fit coefficients that will "predict"/"explain"  anything he wishes (1).
   By the way, it is interesting to compare this "beefed" 6-wraps Double Cow hitch, with a 6-wraps Pile hitch (2)...No relation ( "relevance" (3) :)) whatsoever.

1. http://www.theuiaa.org/upload_area/files/1/sdarticle.pdf
2. http://igkt.net/sm/index.php?topic=4139.msg25030#msg25030
3. http://igkt.net/sm/index.php?topic=4139.msg25045#msg25045

kd8eeh

  • Exp. Member
  • ****
  • Posts: 159
Re: A simpler TackleClamp hitch.
« Reply #29 on: December 04, 2012, 05:37:14 AM »
The reason that more wraps improves the ability of a hitch to withstand lengthwise pull is not so complicated as you make it seem (at least to me).  If you have more wraps, then when you pull lengthwise on one end of the rope, you are not making it into an elipse as much.  I can't quite solve the integration associated with it, but if a force is applied twisting one wrap around the pole, that wrap truns into an elipse.  Then the normal force must act to keep the elipse from rotating.  I belive this to be somehow proportional to the secant of the angle the wrapping makes with the pole; the normal force goes to infinity as the wrapping is closer to perpendicular.  Therefore, if you have your hitch become less eliptical, then the normal force between it and the pole increases.  It follows that the more wraps you have, the more of a complete cylinder you form, meaning that it will twist less when the force is applied, meaning that you will have a much grater normal force resulting in much more friction.