Next generation snatch block

[ntsqd]

That was the curious thing about the knot failures. No residual heat in the fibers on immediate post-failure inspection, but the failure clearly was from some mechanism that left a slightly melted signature behind. Like when you use a cig lighter on a cheep poly rope to fuse it's tiny strands together, looked a bit like how those strands look before they become a bigger blob. My observation based speculation is that the tight bends in a knot, which when constricted by a load tightening the knot, causes extremely localized heat that failed each strand more or less one at a time. EDIT: I should mention that the location of these failures was always where the first tight loop around the live end constricted down on it. In other words, the failure was always right at where the live end entered the knot.

W/o prior experience with them I'd be inclined to run it on the chafe guard. I'm guessing there's a reason that I'm not seeing that causes you to advise differently.

 

[DaveInDenver]

No residual heat in the fibers on immediate post-failure inspection, but the failure clearly was from some mechanism that left a slightly melted signature behind.

Sampson seems to agree with you that there does not need to be any obvious appearance of what we'd call melting for damage to occur. Amsteel Blue is HMPE.

This taken from their rope manual: https://www.samsonrope.com/resources/commercial-marine/rope-manual

 

[Metcalf]

That was the curious thing about the knot failures. No residual heat in the fibers on immediate post-failure inspection, but the failure clearly was from some mechanism that left a slightly melted signature behind. Like when you use a cig lighter on a cheep poly rope to fuse it's tiny strands together, looked a bit like how those strands look before they become a bigger blob. My observation based speculation is that the tight bends in a knot, which when constricted by a load tightening the knot, causes extremely localized heat that failed each strand more or less one at a time. EDIT: I should mention that the location of these failures was always where the first tight loop around the live end constricted down on it. In other words, the failure was always right at where the live end entered the knot.

W/o prior experience with them I'd be inclined to run it on the chafe guard. I'm guessing there's a reason that I'm not seeing that causes you to advise differently.

Yup, the knot failures are generally all about violating the D/d ratio for bend radius on dyneema products.

When used with a snatch ring, the chafe guard has a bad habit of rotating around the core and destroying itself and causing damage to the line.
The UHMWPE has a nice low coeffecient of friction and is really ideal when used with the snatch ring.
With the way I tie my soft shackles with the 'improved' design, the two legs also give much more area for the bearing surface.

 

[MartinDWhite]

I worked with a local machine shop to make a small run of these for me and some friends, the extras are up on ebay. These have worked great for us. Check them out on ebay if you want one. http://ebay.us/LXTvGw?cmpnId=5338273189

 

[Wilbah]

Thank you all for a great discussion, I'm learning a lot. Would these "rings" perform better (less damage to the line) if they had a larger diameter? Or is the real concern the heat induced weakness to the soft shackle? In that case (if I'm thinking about this correctly), unless the "core/center" of the ring were thickened dramatically (a larger radius for the softshackle to slide around) then it wont matter (if the line itself going around the ring doesn't get harmed)? Or maybe even then it wont make much difference?

As I've seen "how to's" for how to make a soft shackle (I don't trust myself yet to do this) maybe it's just easier to have extra line, let the soft shackle be the "wear item", and replace it (make a new soft shackle) after some number of pulls?

 

[gungriffin]

I really want to love the concept of a snatch ring, but real data that someone posted shows that they have big issues with friction. This was something that people have mentioned and it was dismissed. The numbers in the video below don't look good for the rings. I will be sticking to my ARB 9000 snatch block.

 

[RacerAV]

Bend radius is too small for wire rope, and a large enough block would be difficult to get stiff wire rope to lay into correctly.

I emailed them a technical question about friction losses versus traditional snatch blocks.

Solid aluminum blocks are used in climbing, sailing, arborist work, etc, but normally for light duty/light load scenarios.

This is appealing for adding as a third or fourth block in my rig for the rare occasions I need that much redirection, but I don’t see it replacing my ARB9000s for primary use unless the friction numbers are really close or better (doubtful they could be).


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Agreed 100%. Wouldn’t mind keeping this in my kit for an extra point of pull but for the main SB? I’ll Stick to my Warn SB. Love the innovation!

 

[Metcalf]

I really want to love the concept of a snatch ring, but real data that someone posted shows that they have big issues with friction. This was something that people have mentioned and it was dismissed. The numbers in the video below don't look good for the rings. I will be sticking to my ARB 9000 snatch block.

It is an interesting test. Having data is good. I am just not seeing the same thing happen in my testing. I'd love to have a load cell to test this stuff out in a similar manor. I do have some significant differences in how I am setting up and running my snatch rings.

 

[Metcalf]

Thank you all for a great discussion, I'm learning a lot. Would these "rings" perform better (less damage to the line) if they had a larger diameter? Or is the real concern the heat induced weakness to the soft shackle? In that case (if I'm thinking about this correctly), unless the "core/center" of the ring were thickened dramatically (a larger radius for the softshackle to slide around) then it wont matter (if the line itself going around the ring doesn't get harmed)? Or maybe even then it wont make much difference?

As I've seen "how to's" for how to make a soft shackle (I don't trust myself yet to do this) maybe it's just easier to have extra line, let the soft shackle be the "wear item", and replace it (make a new soft shackle) after some number of pulls?

There is a minimum advised bend radius for a moving 'bend' with synthetic lines. That is usually 8-10x diameter with a little wiggle room to go smaller depending on speed.

Spreading the bearing load out on the soft shackle is a good thing. I like using the 'improved' soft shackle design with the twin legs. This gives you more surface area to reduce the friction. Making sure to use just the UHMWPE as the interface surface works best in my experience, the nylon wear guards don't do as good of a job ( and can be spun on the shackle creating damage.

I've been doing pretty extensive testing on this concept for over a year now. I have yet to wear out one soft shackle. I doubt most people are going to be doing THAT much full double line pulls. The soft shackle would last a long long time.

 

[shade]

There is a minimum advised bend radius for a moving 'bend' with synthetic lines. That is usually 8-10x diameter with a little wiggle room to go smaller depending on speed.

Spreading the bearing load out on the soft shackle is a good thing. I like using the 'improved' soft shackle design with the twin legs. This gives you more surface area to reduce the friction. Making sure to use just the UHMWPE as the interface surface works best in my experience, the nylon wear guards don't do as good of a job ( and can be spun on the shackle creating damage.

I've been doing pretty extensive testing on this concept for over a year now. I have yet to wear out one soft shackle. I doubt most people are going to be doing THAT much full double line pulls. The soft shackle would last a long long time.

Ever try a dry lube? As long as it didn't attract debris or attack the synthetics, it could decrease the friction significantly.

 

[Metcalf]

Ever try a dry lube? As long as it didn't attract debris or attack the synthetics, it could decrease the friction significantly.

I've never had any evidence that friction has been an issue with the UHMWPE soft shackle on the smooth aluminum in my testing.

The coeffecient of frition should be as low as 0.10-0.14-ish in a dynamic application.

I spread the bearing load out over both legs of the soft shackle in my design. I also use my little 'block' to help keep things organized and prevent a 'pinching' load hot spot on the smaller outside radius of the ring.

 

[shade]

I've never had any evidence that friction has been an issue with the UHMWPE soft shackle on the smooth aluminum in my testing.

Other than having a way to measure the load, evidence of wear and heat are probably good enough indicators. ?

 

[Metcalf]

Other than having a way to measure the load, evidence of wear and heat are probably good enough indicators. ?

Absolutely, and I have had no evidence of wear and heat being a significant issue. Have you? I agree that in THEORY these could be issues, just not in practical application.

I've ton a lot of testing on this concept including multiple full pulls at 8274 winch speeds. I've yet to see any significant wear on the soft shackle or even make the aluminum snatch ring warm to the touch. I don't know how fast, far, or often people are doing recovery operations, but I have at least a few dozen of my little kits out there all across the country. I have yet to have anyone come back with heat related issues.

 

[shade]

Absolutely, and I have had no evidence of wear and heat being a significant issue. Have you? I agree that in THEORY these could be issues, just not in practical application.

I've ton a lot of testing on this concept including multiple full pulls at 8274 winch speeds. I've yet to see any significant wear on the soft shackle or even make the aluminum snatch ring warm to the touch. I don't know how fast, far, or often people are doing recovery operations, but I have at least a few dozen of my little kits out there all across the country. I have yet to have anyone come back with heat related issues.

Nope, I haven't used a snatch ring; just following the discussion to learn more about them.

Assuming the shackles & rings are proper, my guess is that most issues could be related to really dirty conditions leading to increased friction. Even then, it might take a lot of abuse before doing any harm. Do you think a winch line that was heavily saturated in sandy mud might eventually chew something up enough to make a difference?

 

[Metcalf]

Nope, I haven't used a snatch ring; just following the discussion to learn more about them.

Assuming the shackles & rings are proper, my guess is that most issues could be related to really dirty conditions leading to increased friction. Even then, it might take a lot of abuse before doing any harm. Do you think a winch line that was heavily saturated in sandy mud might eventually chew something up enough to make a difference?

The winch line 'travels' with the ring generally isolating it from wear. Those surfaces typically are not sliding.

The wear in the system is to the soft shackle and the ring itself. Eventually those parts might wear out, but I haven't seen it happen yet. There are wear parts in a normal snatch block too. They get dirty. They are not generally sealed systems....they are just some bushings. How often do you see them wear out?