Amsteel Blue Splicing Experiments

[pdqdl]

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.

 

[Philobite]

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.

 

[moray]

...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.

 

[pdqdl]

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.

 

[moray]

...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!

 

[pdqdl]

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.

 

[moray]

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...

 

[pdqdl]

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.

 

[moray]

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

Excellent!

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.

 

[pdqdl]

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!

 

[moray]

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?

 

[pdqdl]

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.

 

[moray]

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.

 

[pdqdl]

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.

 

[RUBE]

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.

 

[pdqdl]

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.

 

[RUBE]

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.

 

[flushcut]

An oldie but a goodie.

 

[pdqdl]

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.

 

[moray]

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

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.