# Amsteel Blue Splicing Experiments



## moray (Apr 18, 2008)

I had wanted to play with some Amsteel Blue for some time, partly because it is one of the strongest of all ropes, and partly because I thought it might make a good replacement bridge for my harness. Amsteel Blue is Samson's strongest version of high molecular weight polyethylene (HMWPE), the same stuff from which Spectra is made. It is stronger than steel, floats on water, and the 3/16 in. version is rated at 5400 pounds breaking strength.

Mine came from Redden Marine in Seattle (47 cents/foot, 20 feet, prompt delivery). It is very cool material. Here are some of the things I found from 10 days of testing:

It is STRONG!

It is slippery. I watched a triple fisherman's knot start unwinding under load until it got really tight; then it held.

It is very hard to cut with scissors. A very sharp pocket knife cuts it OK, but the fibers have to be held taut while cutting.

It can take rough handling. In some of my experiments, the same piece was spliced, loaded, taken apart, respliced in some other way, loaded again, and so on. It showed much less degradation from this sort of treatment than a similar piece of polyester would have.

It is ridiculously easy to splice. 

Splices are reliable. None of my splices, even ones considerably shorter than standard, ever pulled apart.

In the next post I'll describe splicing equipment, and then move on to the actual experiments.


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## moray (Apr 18, 2008)

*Materials*

The wire fid is just a piece of 12 gauge electrical wire, about 18 inches long, with an eye soldered in one end. The white yarn is polyester from some old rope. (To give proper credit, the ideas here are very similar to those behind the Brion Toss Splicing Wand.)







Before inserting the fid, first lock the white snare yarn around the eye in a sort of girth hitch.






Next insert the fid where the tail is to emerge. Exit the rope where throat of the eye will be.






Loosen the snare yarn to make a loop, as in the first photo. Snare a few strands of the Amsteel Blue (AmB from now on), as shown in the last photo, pull hard on the snare yarns to tighten the captured strands of AmB hard up against the copper eye. Then pull the captured rope into itself to form the eye. Simple.






This very same wire fid, incidentally, works fine on much larger 12-strand rope, such as Tenex, but I am thinking of making a stiffer version with 2 or 3 copper wires soldered together.

Later I'll post info on the actual experiments.


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## moray (Apr 18, 2008)

*Loop Experiment*

Using AmB as a possible replacement for my saddle bridge was of some interest to me, so I needed to make something about 9 inches long, and I wanted to make it in place--no taking the saddle apart to install it. But you can't make a splice as short as you want. There is a minimum length specified by the manufacturer--Samson in this case--that is supposed to work. In the case of 3/16 AmB, the buried core consists of 8 inches of full-diameter rope terminated by a 4-inch tapered section to give a smooth transition between the thick spliced area and the undisturbed rope beyond the splice.

The absolute simplest way I could meet my spec and Samson's spec at the same time was to make a loop with a single splice, as shown below. This is the ONLY splice, in all my experiments that actually meets the manufacturer's spec. 






Unfortunately, the loop does NOT meet Samson's spec for splicing a continuous loop. This requires TWO splices. The free tail in mine should be about 12 inches long, and it should be buried in the top half of the loop in exactly the same manner as the bottom half was done. I have made plenty of loops in this manner, which are perfectly symmetrical, and they have been entirely reliable.

Nevertheless, I decided I would test my "half-spliced" loop. I rigged up the AmB loop with a 2-ton come-along stretched between two vehicles. To make the test as severe as possible, one of the pull points was attached just where the core emerged from the splice. If any pulling configuration was going to pull the splice apart, this was it. The picture below shows the loop loaded with a few hundred pounds.






This picture shows the other pulling point. Note the lower, spliced, leg is somewhat thicker at the left, but has tapered down to normal thickness before it reaches the screw link on the right. The end of the bury is probably about 1/2 inch from the screw link.






After the pictures were taken, the tension was taken up till one of the vehicles started skidding and I feared for the integrity of the come-along. I guessed the tension was at 3000 lbs or so. There was no sign when I inspected the splice later that there had been any slippage.

This was a surprise to me, as I didn't expect the unsymmetrical "half splice" to perform as well as a properly done symmetrical loop. If I were ever tempted to use the half splice, I would make sure the bury section was bent around one of the load points; this should help to lock the bury in place.

The rest of the experiments, upcoming, all involve spliced eyes, some of them very non-standard.


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## safeT1st (Apr 18, 2008)

*Interesting Work*

Hat's off to you for your experimenting . Am I correct in understanding the splicing technique is simply pulling the line through the body of the line for the correct distance ? Please describe how you achieve the "tapered section" of splice . Would it be wise to somehow mark the line so you could tell at a glance if the splice had begun to retreat ?


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## moray (Apr 19, 2008)

safeT1st said:


> Hat's off to you for your experimenting . Am I correct in understanding the splicing technique is simply pulling the line through the body of the line for the correct distance ? Please describe how you achieve the "tapered section" of splice . Would it be wise to somehow mark the line so you could tell at a glance if the splice had begun to retreat ?



Good questions. I do mark the splices at the throat so I can see right away, after a load experiment, if anything has moved. For a finished splice meant for use, I stitch the throat more or less to manufacturer's specs. The stitching would have to unravel or stretch or break, which you could see, if the splice were starting to come apart. I have never seen it happen.

Yes, making the splice is as you describe. Once you have pulled the tail out at the insertion point, and the eye is the correct size, you smooth and stretch the cover from eye to tail so all slack is removed. Now mark the tail where it exits the rope--this will be the tip of the bury. Now pull on the tail and push the cover back towards the eye. Cut the tail off where you marked it. Unravel a few inches to make a taper (but don't disturb the main body of the bury). Say you plan to taper 3 inches. You could cut one of the 12 strands right at the 3-inch mark, another 1/4 inch longer, and so on, leaving the final strand uncut. Now go back to the eye and smooth the cover back towards the tail. The freshly tapered tail will get sucked back into the rope and you're done!

If you visit Samson's web site, there's a link there to their splicing section. Once there, pick Class II 12-strand eye splice to see the instructions (with nice diagrams) that apply to Amsteel Blue.


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## moray (Apr 19, 2008)

*Side-by-Side Splice*

In splicing short Eye and Eye slings, it is often necessary to overlap the tapered tail from one eye with the tapered tail from the other. When well done, the result is a nearly uniform rope diameter from one eye to the other. Even though I knew the 9 inches of my saddle bridge was way too short to accomodate 2 legal spliced eyes in 3/16 AmB, I thought I would go through the motions anyway. I soon discovered that AmB is roomy enough inside to hold 2 full-diameter ropes side by side! This is practically impossible with Tenex, and it offered up a new possibility for the short sling.

I made up a double-eye sling in which each buried tail extended the full length of the rope and emerged at the throat of the other eye. The distance between the eyes was about 5.5 inches, much shorter than the prescribed minimum of 8 inches. I went directly to the pull test without bothering to taper and bury the tails. My friend Jack and I hooked it up between two of his trucks and he started pulling while I took photos.






He towed his 5000-lb tree truck, brakes locked, about 5 feet down the driveway before giving up. One of the splices had slipped an inch or two before locking up, and the whole sling had become stiff. When I later massaged it back to normal pliability and pulled it apart, I encountered a surprise. The inner surface where two cores were crushed together was dead flat and mirror smooth. The cross section of each core, in other words, was a perfect semicircle. The outer surface of the semicircle was rough as a pineapple--the weave pattern of the cover had imprinted it like a waffle iron, providing, presumably, great gripping strength. The roughness can be seen in the photos below. Each photo also shows a bit of rope with a normal surface.










Even though I was impressed that a much shorter than standard splice worked in this configuration, and even though the side-by-side splice was not hard to make, there were several things, engineering wise, that I didn't like about it, and I went on to better ideas. The next experiment was my favorite.


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## moray (Apr 19, 2008)

*Bury-in-Bury Splice*

If the previous splice was a deviation from accepted practice, this one was even more so. Instead of burying 2 cores side by side, in this experiment one core is buried inside of the other.

As always, to make the tests really conservative, the splices are much shorter than manufacturer's spec. First I made an ordinary eye and left a long tail hanging out of the rope. By inserting the wire fid at the throat of the eye just formed, and running it right down the center of stuffed core, I could bring it out of the tail half an inch beyond where the tail emerged from the cover. Then the rope was pulled through to form the second eye. The pictures should make this clearer. The end result is that for the full distance between the eyes you have a rope in a rope in a rope--3 concentric layers of rope. All the strange asymmetries of the previous experiment are gone!

The load testing showed some initial adjusting as the cover and two cores stretched into some sort of equilibrium, like setting and dressing a knot, but then the splices held. This seemed like a really promising design.


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## moray (Apr 19, 2008)

*Bridge Test*

A new example of a bury-in-bury sling was made up, this time for testing in a saddle bridge configuration. The first photo shows the sling being pulled by the tree truck. The sharp bend in the middle of the sling (upper part of photo) is very close to what a saddle bridge would experience.

I was sure it would not pull apart, but I wondered if some of the fibers at the outside of the bend might break. None did, but I would expect that to be the most highly stressed part of the rope. This same sling was then used in the next test.






How would this test bridge stand up to repeated flexing as the load point moved back and forth the length of the bridge? To test this, I attached a foot loop to each eye and hung the center of the sling over a suspended carabiner. By carefully adjusting the carabiner height, one foot would be resting on the ground when the carabiner had reached the throat of the opposite eye. When I would then step with the other foot, my full weight would be on the carabiner, and the sling would slide through the carabiner until the foot hit the ground and the other eye reached the carabiner. I did 400 teeter-totter steps in this manner, getting in my exercise for the day, and then examined the rope.






There were no broken fibers. The rubbed surface appeared lightly polished and slightly flattened. (The white yarns showing in the photo are loose ends from my hasty stitching.) 

Intriguing as it was, the bury-in-bury splice was too hard to make to seriously consider for a bridge replacement. But I had not given up on the desire to have a simple eye of some kind to attach to the suspension rings of my saddle.


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## moray (Apr 19, 2008)

*Ring Splice*

This next-to-last splice was an attempt to keep a simple eye for attachment to the saddle suspension ring, but add some friction that would help prevent the tail from slipping out of the short splice. The result was interesting, but the effort was misguided...






To make the splice, the rope passes around the ring, then enters the rope at the arrowhead pointing to "1st bury", then passes around the ring again, this time inside the rope. It emerges right under the black arrowhead and finally the tail is buried in the main rope at "2nd bury". After I admired it for a few moments, I realized the cover was highly distorted at the "1st bury" location, and any load would only tend to make it worse. Definitely not the first bad idea I ever had.

But this brought me to the final experiment: a hybrid of a knot and a splice. The Samson splicing specs are clearly designed to handle a worst-case scenario: an eye that is unsymmetrically loaded so the entire load is on the buried leg. That is why my very first experiment didn't pull the splice apart. But if one could guarantee the buried leg would never carry much load, then a very short bury would be sufficient to hold the tail in place. A big secure knot like a figure eight follow through or a triple fisherman's wouldn't need the tail to be buried at all. A really simple knot like an overhand would definitely require the tail to be buried, but even an overhand knot would greatly reduce the load on the tail. The idea is still to splice an eye, but the loop of the eye will now be involved in some sort of a knot around the ring.


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## safeT1st (Apr 19, 2008)

*Motivation*

This looks like amazing rope you are working with . I think I will look at ordering a section as you did just to experience it myself . I have to ask you though ; what is motivating you to do this ? What advantge will there be to this 3/16 " bridge ? In my mind there has to be a substantial advantage to it otherwise not only are you trying to re-invent the wheel but you are treading into unknown waters .

Repectfully , 

safeT1st .


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## moray (Apr 20, 2008)

safeT1st said:


> ... I have to ask you though ; what is motivating you to do this ? What advantge will there be to this 3/16 " bridge ? In my mind there has to be a substantial advantage to it otherwise not only are you trying to re-invent the wheel but you are treading into unknown waters...



The short answer is: education and pleasure. No advantage, highly impractical. I could just buy a replacement bridge, like everyone else! But this way I learn lots of cool stuff, get to handle exotic materials, impress my friends with tiny little ropes that can lift a loaded truck, and so on. Most of all I like the mathematical and engineering aspects of this stuff--it's an endlessly fascinating puzzle. As to re-inventing the wheel, it is the first time _I_ invented the wheel, and I am sure I get the same charge out of it as the first person who did it.

I hope you follow through and get yourself a few feet of AmB. I can't imagine a better rope for experimentation or for learning to splice. Good luck!


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## safeT1st (Apr 20, 2008)

*I Agree*

Yes , I agree with you describing learning new things and experiences . Seems like alot of people have little interest in broadening their horizons . I really need to get me a piece of that stuff .


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## moray (Apr 20, 2008)

*The Knot*

ANY knot would provide lots of friction to help secure the buried tail, but the knot configuration had to unconditionally guarantee that the whole arrangement could never become unsymmetrically loaded so that the tail was taking the brunt of the load. The girth hitch seemed perfect. Since the only point of the knot is to supply friction, and thereby remove load from the tail, how well does the girth hitch in Amsteel Blue on an aluminum ring perform?






The hammer in the photo weighs about 3 lbs. With my full weight (155 lbs.) on the other leg of the hitch, I was just barely able to raise the hammer. The next handy weight I found was a gallon of antifreeze, about 8 lbs. This I could not move at all. There is no need for great accuracy here; I conclude that the girth hitch gives a 30:1 advantage. One leg can resist a pull from the other leg with only 1/30th the force.

The final experiment is next...


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## moray (Apr 20, 2008)

*Testing the Hybrid*

The first photo shows the "bridge" ready for testing. The other two photos show the individual eyes. They are intentionally quite different in size, just in case size was a relevant parameter. Both eyes were carefully marked where the core entered the cover.
















The bridge and the come-along were rigged up between a car and a tree. This time the bridge was repeatedly loaded by backing up the car. These were dynamic loads of unknown size, but certainly in the range of 1000 lbs. and up. After 7 successive trials, the car was parked with brakes set, and a static load was applied with the come-along. At the point when the car just started to skid, the sling was left under tension for 5 or 10 minutes. 

It was noted after the experiment that the sling was perhaps 1/2 in longer than before. Since there is very little stretch to HMWPE fibers, this stretch must appear as tension removes all the constructional slack in the splice. Neither of the two eyes had experienced any slippage whatsoever, and there was no apparent reason from this experiment to prefer one over the other. The small eye does have a longer bury, and that might be a reason to prefer it.

In conclusion, 3/16 Amsteel Blue turned out to be marvelous stuff--a pleasure to handle, easy to work with, and amazingly strong. I'm sure I'll find some use for the 9 feet I have left--a couple of pigtails for my ascenders, perhaps, or maybe a replacement bridge for my saddle. The most interesting thing in all this for me, though, was a better understanding of knots and splices. They are very close cousins, and a hybrid of the two, as in this last experiment, can do a job that neither could do alone.


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## ckliff (Apr 20, 2008)

Correct me if im mistaken, but isnt AmB also known as True Blue? If so, the Sherrill catalog lists it as NON-spliceable. I recently purchased some 12-strand which is purportedly the only spliceable 12-strand on the market. Dont remember its name, it is white with orange & green specks.


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## moray (Apr 20, 2008)

You would think there are enough words out there that the manufacturers could come up with distinct names. True Blue and Amsteel Blue are very different. The reason True Blue isn't spliceable is because it is a solid braid. Some smart inventor could probably find a way to splice it using some interweaving technique similar to the method used with 3 strand. When the splicing gets too hard, I tie a knot.


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## rbtree (Apr 30, 2008)

True blue can be spliced, but it isn't easy. Not by me....

moray, and anyone who wants to get great deals, contact me. My Seattle supplier gets me rope at about 60% off retail.....for instance, 1/2 inch Plasma (equal of Amsteel Blue) for about $1.80 per foot....and 1/2 inch double braid for maybe .60 coated...haven't checked lately, for the inevitable price increases.....


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## Philobite (Apr 30, 2008)

Moray,

Thanks for your splicing pics and words.

I've been using AmSteel Blue 5/8" x 160' on a CAT D7/Hyster Winch to skid logs for over a month and so far I have to say I absolutely love the stuff. It's easy to drag out to set chokers and it's so light I can run rope off the spool by myself (almost impossible with wire rope bull line). I've already snapped two 1/2" wire rope chokers with it, so it's plenty strong.

I'll be moving the termination point soon so paying attention to splicing techniques will be helpful to me.


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## pdqdl (Apr 30, 2008)

Philobite said:


> ...
> 
> I've already snapped two 1/2" wire rope chokers with it...



Since the rope is so light and strong, I would expect it to take the weighted end with the choker parts still attached and behave like a well aimed cannon at the back of the towing vehicle.

Isn't there a much greater tendency for the light rope to fly away under a broken load than would the heavy wire rope (away from the load, in the direction of the pull) ?


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## Philobite (Apr 30, 2008)

pdqdl said:


> Since the rope is so light and strong, I would expect it to take the weighted end with the choker parts still attached and behave like a well aimed cannon at the back of the towing vehicle.
> 
> Isn't there a much greater tendency for the light rope to fly away under a broken load than would the heavy wire rope (away from the load, in the direction of the pull) ?



Actually, with the AmSteel Blue both times the wire rope chokers broke, the AmSteel rope with choker chucks and other heavy stuff at the end simply fell to the ground like a wet noodle. It jumped toward the CAT maybe two feet with 30 feet of rope out. Very safe. The rope does not store energy in the tension like wire rope bull line does. That's one of the reasons I selected it.

I've broken chokers with 5/8" steel wire bull line and the back of the CAT safety cage has the scars to show it. Very scary.


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## pdqdl (Apr 30, 2008)

I am getting very interested in this rope. Breaking strength seems unbelievable. Recent posts about using it on a winch setup are very appealing, too.

Does anyone have any experience with failures using the rope? 

When overloaded, how does it fail? Does it melt together on the winch drum; does it break with a pop, or does it tear apart slowly?

How much friction can it take going over obstructions like other tree branches ? 

All comments will be appreciated.


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## Philobite (Apr 30, 2008)

Typical failures would be from heat abrasion and would occur at the point of abrasion. For example I use a slider choker chuck. If I had two massive logs 30 feet apart and facing each other end to end, and set my bottom choker on one, then my second choker on the second slider chuck and then on the opposite log, and then took off like mad in the CAT, there would be tremendous pressure, heat and abrasion right at the second slider where the rope passes through it. I could expect a heat/friction failure right there.

Another failure would be passing over a sharp rock or piece of metal, or even a hard, sharp edge of wood when under great tension. That is a no-no, as it would cut the rope.

The third failure would be long term wear right at the termination of the rope where it's spliced around a metal ring where the choker chuck sliders come down to rest under load. Over time that point is going to wear down. So before then I'll need to undo the splice a little, slide the rope further up by a few inches and re-fixture the splice to move the pressure point.

The fourth failure is just abrasive wear and tear one braid at a time.

The bottom line is: avoid heavy and speedy side tension/friction (keep the tension straight), watch out for catching in fair-lead roller corners or around bolts on the side of a winch, don't tension over or around logs or rocks, and don't tension down into the soil, like over a dirt berm or road edge.

The nice thing is that it usually fails at the business end so you can buy another 30' of rope, splice it in, rotate ends on the rope and you're back in business. Try that with a wire rope.


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## moray (May 1, 2008)

Philobite said:


> ...I'll be moving the termination point soon so paying attention to splicing techniques will be helpful to me.



Philobite, the description of your heavy-duty winching operations is really interesting. There is some good news when you get around to terminating the rope with a new eye: you don't need a fid. The basic instructions for making the splice are given here:

http://www.samsonrope.com/site_files/12S_C2_EyeSpl.pdf

Just remember, that for your 5/8" rope, one fid length is 14 inches.

I just spliced an eye in 5/8" Tenex a couple of days ago without a fid and found it quite easy. Mark the rope according to the Samson instructions. Tightly tape the tapered end a half inch or so back from the tip--it helps to have a sligtly brushy tip to avoid snagging inside the cover. At the point where the rope is to be inserted, open the rope with your fingers till there is room to easily insert the taped end. From there it is a matter milking the core into the cover like one snake swallowing another. The process is slow at first, but gets very easy once 4 or 5 inches have been buried. Pulling the core out at the end of the bury is very easy. Once you get the hang of it it won't take more than 5 minutes to perform the entire operation. Next, do the stitching at the eye throat. Lastly, do the final taper according to instructions, suck in the tail, and you're done.


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## pdqdl (May 3, 2008)

*Bought some 3/8ths amsteel*

Based on you guy's comments, I bucked up and bought 150'. I plan on using either on my 12,000 lb crane as an extension to the shorter cable on it now (it uses 3/8 wire rope), or as the primary line for my portable capstan rope winch.

My guys melted the 9/16 stable braid in half with the capstan rope winch. Idiots didn't have the sense to back off the feed pressure when the load wasn't moving anymore. Yep, I was pissed. 

They all have a good understanding of how to use a portable winch, after I got done politely explaining it. For the third time.


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## moray (May 3, 2008)

pdqdl said:


> ...or as the primary line for my portable capstan rope winch.
> 
> My guys melted the 9/16 stable braid in half with the capstan rope winch.



Your composure, even on the 3rd explanation, is an example we can all aspire to! 

Remembering back to our long discussion of rope friction around a post, here you have it. The Amsteel Blue, a form of polyethylene, will melt at about 260 degrees F, compared to polyester at about 480 degrees. Even where it is plenty strong for the job, it will melt before a much weaker rope. Except in the case of very light loads, you probably won't get away with letting AmB slip on your capstan winch. Because it is so slippery, you might need an extra wrap to hold a load. Sounds like you have some interesting experimenting ahead of you. Good luck!


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## pdqdl (May 3, 2008)

Ah yes. But the slipping on the post wasn't the problem. 

In addition to my idiots keeping the pressure on the rope with the engine racing for several minutes while we were cutting the log with a saw, the capstan simply is not supposed to be used with that thickness of rope. The large diameter of the rope kept my men from using enough wraps to hold the load easily. It melted down on the side of the capstan that they were pulling on, not the loaded side that the engine was pulling with.

Next time we get in spot like that, they have been adequately notified that they are not to "hold" a load by slipping the capstan. Even though it is slicker than the stable braid, I'll bet the extra 3 wraps we can fit on the capstan will more than make up for the slicker rope.

Next time, if we operating at the limits of the single line pull, I'll tell my guys to put on another pulley and double the power. I never dreamed they could melt a rope in half. I had already showed them how to work a load, how to handle a stall on the winch, etc. 

I still think they might have done it because they were mad at me for giving them a job they didn't like. They didn't want to take the winch, they didn't want to get their feet wet (the tree was spanning a creek you could hop across), they thought they should drag a rope over the hill from a truck and pull it up the hill, etc. That and they don't like to take any instructions; from me or anyone else. You see, they know what they are doing and they don't need my opinion.


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## moray (May 4, 2008)

pdqdl, amusing as your words are, a picture would be even better. How about posting a short video that captures one of your instructional sessions with your "idiots"? Be sure and show their upturned faces, rapt with attention, as your calm and patient voice explains, for the third time, how not to burn through the rope...?

When you mentioned it took minutes to melt the rope, I began to think I had been overly pessimistic about using Amsteel Blue on a capstan winch. How fast would the rope heat up if the load was stopped and all the winch power was generating friction heat on the capstan?

I had to make some assumptions:
1. Capstan is made of steel and weighs 5 lbs.
2. Load is 1000 lbs.
3. Winch speed is 30 ft/min.
4. Capstan diameter is 3.5 inches.
5. Rope is Amsteel Blue, 3/8 in, 3 wraps around capstan.
6. As heat builds up, it is instantly distributed through the capstan and rope wraps.
7. Heat dissipation to the outside air is ignored.

The first 3 are the ones that really matter, and tell us that 675 watts of power are heating the capstan.
To turn that into temperature rise, you need a coefficient, the specific heat capacity, for both the rope and the steel. For steel the number is .74, and for polyethylene it is 1.9. It takes more than 2.5 times as much energy to raise a pound of PE by 1 degree as it does to raise a pound of steel by 1 degree. For water the coefficient is 4.2, one of the highest known.

It turns out the mass of rope in contact with the capstan is only about 2% of the mass of the capstan, so it could safely be ignored for the calculation, but I included it anyway... I'll show my actual numbers if anyone is interested.

The result surprised me. The combination of capstan and rope increases 41 degrees F per minute, or only .69 degrees per second. Somehow I was expecting it to reach the melting point in about 5 seconds!

Assumption #6 is necessary if we don't have any hard numbers about heat flow, but in view of the very slow rise in temperature, it is probably pretty accurate. If there were a lot more power involved, or if you only had half a wrap of rope, then the local heating of the rope could cause a hot spot at the friction surface that would melt it long before the overall system had accumulated much heat.

Let us know when you actually put it to use...


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## pdqdl (May 5, 2008)

Regarding video: I think this forum prohibits the distribution of the kind of intructional messages I was using that day.

When I was using the rope winch to pull the rope in patient instructional lesson #2, immediately prior to the meltdown, I found that the rope was getting uncomfortably warm to my bare hands when I was feeding it. The 50cc chainsaw was locked open on the throttle, and it was necessary to pull hard on the feed rope to move the logs. Rather than binding on the capstan, the rope would continue to slip unless you pulled real hard on the feed rope.

To much load, rope was too fat to get enough wraps to hold with an easy feed pressure. I would guess that they loaded the rope on the winch for at least 3 minutes, stopping just short of stalling the winch. I had previously told them to NEVER stall the winch, because it would ruin the clutch on the saw (patient lesson #1, where I told them not to smoke the clutch, that it wouldn't hurt anything to take the load off the winch and let the rope freewheel on the capstan). The "freewheel" concept was apparently lost on them.

I think the 3/8th amsteel will work much better, but I will be very watchful for meltdowns.

By the way, the capstan is aluminum, about 2 1/4" diameter, with a drum width of 2.75". Four wraps fits well for the 9/16" stable braid, 5 wraps is overlapping a bit, but really pulls then.


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## moray (May 5, 2008)

pdqdl said:


> Regarding video: I think this forum prohibits the distribution of the kind of intructional messages I was using that day.



Excellent! 



pdqdl said:


> By the way, the capstan is aluminum, about 2 1/4" diameter, with a drum width of 2.75". Four wraps fits well for the 9/16" stable braid, 5 wraps is overlapping a bit, but really pulls then.



Aluminum conducts heat about 5 times better than steel, so my assumption #6 is probably quite good--the whole system is at the same temperature at any moment. Aluminum has a bit more heat capacity than steel: .96 vs .74. But it weighs less. Assuming your capstan weighs 3 lbs, the calculations still show a very slow rise in temperature of 53 degrees per minute with a load of 1000 lbs and a capstan speed of 30 ft/min. The Amsteel Blue should work just great if you make sure the winch is either pulling or freewheeling but rarely just sitting there slipping and building up heat.


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## pdqdl (May 5, 2008)

I think there is a flaw in your calculations. There does not seem to be any allowance for the horsepower applied nor the work done.

Even with a static load [no work done] and the full horsepower of the engine applied directly to the slipping rope, I don't think you have enough variables to calculate heat rise.

I think I would approach the heat rise by a different method. Assume a horsepower for the chainsaw and apply an operational efficiency to the winch. Then put that amount of energy into the mass of the capstan. 

If you assume a 3 hp (output) saw, and a conversion efficiency of 80% (either work done or heat applied to the capstan/rope), then you could calculate the number of energy units [watts, joules, or whatever unit of energy you prefer] converted to frictional energy. Because the load is static, no work is done (apart from stretching rope and anchor points) and all the calculated energy would be converted to heat on the capstan.

Just another approach. I am so far away from my old physics book, I'm not even going to try that one.

Also, I'll bet the capstan weighs only 1-2 lbs, but the entire winch is about 15 lbs. Heat transfer into the gears and case would be purely speculative. It gets heat poured into it from both the engine exhaust, the chain drive & horsepower input, and the frictional heat load from the rope. Pretty tricky to figure a heat accumulation on the capstan from that!


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## moray (May 5, 2008)

*Look Again...*

The 1000-lb load that I assumed, and the 30 ft/min winch speed gives the power. It is 30,000 foot lbs per minute, or 500 foot lbs per second. I converted this to watts, because all the other units I could look up were metric.

As you say, all of the power is pumping heat into the capstan. If you know the shaft horsepower of the chainsaw motor, you can derate it by some reasonable factor as you did, and use that figure for your calculations. The interesting thing the calculations show, and your bozos proved, is for a horsepower or so of input, and a capstan that weighs at least a few pounds, the heat buildup is surprisingly slow. Surprising to me, anyway.

Does a 50cc chainsaw engine really put out 3 HP?


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## pdqdl (May 6, 2008)

moray said:


> The 1000-lb load that I assumed, and the 30 ft/min winch speed gives the power. It is 30,000 foot lbs per minute, or 500 foot lbs per second. I converted this to watts, because all the other units I could look up were metric.
> 
> As you say, all of the power is pumping heat into the capstan. If you know the shaft horsepower of the chainsaw motor, you can derate it by some reasonable factor as you did, and use that figure for your calculations. The interesting thing the calculations show, and your bozos proved, is for a horsepower or so of input, and a capstan that weighs at least a few pounds, the heat buildup is surprisingly slow. Surprising to me, anyway.
> 
> Does a 50cc chainsaw engine really put out 3 HP?



I don't really know what the horsepower is. I imagine that it would do about the same amount of work as a puny lawnmower. My Husqvarna 3120 is supposed to throw somewhere close to 10hp, so I was just guessing backwards. The saw on the winch is a Shindaiwa 488. Pretty good little saw, but I don't even know the cc on it. Just guessing.


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## moray (Sep 4, 2008)

*A perfect use*

I decided to modify my little rock climber's harness by installing two side dee rings made of 3/16 Amsteel Blue. The two eyes are about the same size as large steel dees, and they are part of a normal eye-and-eye sling with full-length buries. The sling is stitched to the back of the harness and to both corners, but the stitching is there only to keep the sling in place and to provide a modest amount of resistance to off-angle forces. 







To keep the eyes open, I inserted a large nylon wire tie in each after first flaming the ends to make them blunt and rounded. The springiness of the wire ties easily kept the eyes nice and round.

How did it work out? On a recent work/vacation in the mountains of Colorado, I got in several hours of real tree work with the little harness and the dee rings worked perfectly. They stayed open and easy to snap into, and showed only negligible wear. They would probably last several hundred hours, which is way more than I am ever going to give them. I checked and replaced the nylon wire-tie inserts after I got home and discovered that they had taken a bit of a set from several hours of loading, but they were still holding the eyes open. It takes about a minute to replace one so it is no big deal.

I conclude that this is a highly practical way to modify a rock-climbing harness to give it strong and functional side dees. You can make the thing at home with a needle and thread, it is as strong or stronger than commercial steel dees, and it is so small you can hardly notice it in your carry-on luggage.


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## pdqdl (Sep 5, 2008)

Neat idea. If the nylon wire ties don't hold up, I'll bet a heavier, more flexible product could be found that would hold up.


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## RUBE (Sep 5, 2008)

Ive been using this stuff as a replacement line for the winch on my CJ7 for 2-3 years now. Its rated stronger than the wire that came with it at the same diameter. It doesnt like knots tied in it and its my theory that the knots generate heat and kaboom broke again. Splicing this stuff is almost easier than tying a knot and seems to be like a broke bone, stronger in that spot. Fun stuff. If your going to be using it around abrasive or sharp stuff add a sleeve over the rope for protection. 

Just used it last week to rappel a friends stump grinder down a very steep bank. He was a little leary of dropping off the bank with a small "rope". "Are you sure about this?" was a repeated question. 

I love the stuff and would never go back to wire again.


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## pdqdl (Sep 5, 2008)

*Knots are problems !*

In addition to the friction created by tightening a knot, there is the inherant weakness created by the knot.

As the rope passes around itself, it creates a longer path on the outside of the curve than on the inside. Since all the fibers are the same length, most of the load gets shifted to the outside of the curve in a knot, and the rope begins to shear fibers, a little at a time until there aren't any left.

Ever see the program where a strongman tries to tear a phone book in 1/2, and then they have a skinny, but well trained housewife rip it in two? Ropes breaking at the knots work on the same theory.

Then there is the monstrous crushing force applied by the knot as it wraps around the rope. Amsteel is pretty slick, so I'll bet it squeezes itself in two.


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## RUBE (Sep 6, 2008)

pdqdl, Im am familiar with the inherent weakness created by knots and you may be spot on with the "squeezes itself in two" theory. I have had some clean breaks or a lack of a tearing failure when Ive tried or tied a few different knots in it. No knots no more for this rope. Only splicing. Even on a straight line with a double I think may be the term. One line goes inside the other, for about 8" than back out about 1" than back in for 6" or so.

Excellent post on splicing by the by. Thanks for sharing.


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## flushcut (Nov 23, 2012)

An oldie but a goodie.


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## pdqdl (Nov 24, 2012)

Yep, ol' Moray does some fine posts. Well worth the bump.

In the intervening years, I should add some of my now-experienced evaluation of the amsteel blue I bought because of this thread.

1. Philobytes comment (post #22) was spot on. His comments should be considered a "how to ruin your amsteel rope" tutorial.
2. Amsteel is just WAY too slick for many applications. I suspect that it is hard to keep on a winch with the normal set screws designed for holding steel cable. I would guess that keeping amsteel on the winch drum could only be done with an eye splice.
3. I have used the amsteel on our capstan rope winch, but it is way too slick. It also melts so easily, that the rope starts melting long before the power of the winch is stalled. 
4. Speaking of slick, the crushing/squeezing power of this rope is hard to imagine. We used a 12" DBH oak tree as an anchor point to help us pull out my stuck chipper truck. With something like 7 wraps around the tree, all it did was crush its way entirely through the bark. OMG! I have never seen anything like it. It killed that tree by doing a spiral bark peel all the way up the wraps that we installed.
5. If you are in the habit of getting stuck far off the road, this stuff makes an excellent recovery rope. Light and strong, I have fished 12,000lb trucks out of the mud with it. Be careful how you attach: it does not tolerate knots at all; so you must either use the full length of the rope or rig your port-a-wrap onto one of the vehicles. Even then, it takes MANY wraps to control the load.


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## moray (Nov 25, 2012)

How cool to see a 4-yr-old thread come back to life. Here's another update on Amsteel Blue.



pdqdl said:


> Then there is the monstrous crushing force applied by the knot as it wraps around the rope. Amsteel is pretty slick, so I'll bet it squeezes itself in two.



About a year ago I had the opportunity to test a 32-kN SMC aluminum ring that someone sent me. The first picture shows the initial setup. I used this setup for 3 sequential pulls (1K, 2K and 3K pounds) to determine the elastic limit of the ring. For all of these pulls the ring was oriented in exactly the same way and the inside diameter of the ring was measured after each pull along the axis of tension. 






The initial value of 1.097 inches was virtually unchanged after the pulls to 1000 and 2000 lbs. Somewhere between 2K and 3K pounds the ring suffered permanent deformation. The ring measured 1.134 inches after the third pull, an elongation of about 1%, and was visibly oval.

For the final pull I wanted to see if filed notches would weaken the ring. I also switched to a clevis from my steel carabiner so as not to deform my carabiner (see setup below).






In the photo you can see a filed notch facing the camera. There is another similar notch 90 degrees around to the left opposite the pin contact point. At both of those locations there are shorter notches on the short sides of the ring, but no notches on the inner surface of the ring.


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## moray (Nov 25, 2012)

What is very cool about doing experiments like this are the big surprises that sometimes await you. That was the case here. The ring did not break near any notch, nor did it get particularly close to its rated strength. It broke where the Amsteel Blue girth hitch was crushing it like a python. 











In the second photo you can see the ring is now out of plane. You can also see, especially on the right half, that the aluminum looks like the rope has crushed it right next to the break. The ring broke at 4880 pounds, about 68% of its rated strength of 32 kN.


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## moray (Nov 25, 2012)

After the ring broke, it was time to explain what had happened.


The first photo is two views of the broken ring. The top view is where the pin had been--note the total absence of crazing. Crazing is very evident in the second view, which shows the midpoint between the pin and the girth hitch. An equal amount of crazing is present at the other midpoint, and at least twice as much where the girth hitch had been. These small cracks are very evident to a fingernail, and they indicate where the aluminum was stretching under the tension.





♠

The next photo shows the ring at an early stage of the pull and a drawing showing a reconstruction of the ring just before failure. It is roughly to scale. 






To me a convincing description of the ring's failure should explain all the following points:
1.Why no crazing at the pin end?
2.Why the odd pattern of depressions at the girth end?
3.Why the pin end has only a barely perceptible footprint from the pin?
4.Why are the upper depressions at the break about twice as deep as the lower ones?
5.Why did the ring break well below spec?
6.Why has the ring been twisted about 10 degrees at the broken end?

This experiment provoked a good discussion on a different forum, but I can summarize here that the Amsteel Blue sling, far from being a passive and ring-friendly device for pulling the ring, turned out to be the active agent behind the ring's premature failure. The large clevis pin, in contrast, did almost no damage to the ring and even protected the ring from stretch in the contact zone.

All the features at the broken end can be explained in terms of the tremendous crushing force of the girth hitch around almost 300 degrees of circumference and the fact that this force was not symmetrical because the hitch was moving slightly as force increased. The ring was being pulled in two and crushed and twisted in half at the same time.


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## flushcut (Nov 26, 2012)

I wonder what the squishing force of the girth hitched Amsb is? I am guessing a lot.


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