That's kinda what I meant - the use of the slick pin for tending means it's now acting "like a pulley", whereas in the normal intended design use as Kevin foresaw it, the RW was in the upper position above the prussik and hence didn't really rotate the pin. Using equipment differently than the original design intent can sometimes have unforeseen consequences. This rotation could potentially cause wear from the rotation of the pin's spring lock (sorry I don't know the name of this thing) against the body of the RW? Which maybe also gives me pause about a question someone asked a few years ago now about their gear experiencing corrosion - they worked near a salt water environment. Once the annodized coating is worn away, the metal might be more susceptible to this also (but I'm fussin here now).The Slick Pin and shoulder bolt on the pulley don’t seem to rotate when loaded while descending, only when tending the hitch upward.
The only thing that I have to say is that engineers are the only guys as cool as tree climbers.Testing the larger thread/fewer stitches: This eye had 17 stitches/pass/side for a total of 102 stitches with 70lb actual strength thread. That's a theoretical strength of 7140 lbs and the jacket of this rope has less friction than the last test piece. I only have cranes at work up to 4000 lbs so I had to get creative. I used a forklift to pick up the back end (counterweight end) of a 10,000 lb rated forklift (8990 lbs on the rear axle per manufacturer data sheet) Let's see how we do:
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I had to stop because I heard the fibers in the rope breaking at the knot and didn't want to add another satellite to space. I wish I knew the actual pull amount but we can get in the ballpark. The truck doing the lifting is rated to 5000 lbs but they can pick up more if the load center is closer to the front tires like it is above. The rear tires on the test dummy were able to be moved by hand so they were significantly unweighted. Let's call this a (very) conservative 6000 lbs. Here's another pic of it under load:
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And here's what the test piece looked like afterwards:
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Note the fibers at the knot beginning to break and the stitching that has gone a little diagonal. Again, seems to be a good indicator of overloading. I'd say we achieved our goal of having the stitching be stronger than the knot. Also, side note, look how the knot rolled under load!
I'd rather have hard data vs. the close estimates I have now. I'm in the process of welding up a break test stand and will report back when it's done. So far I have the I-beam, cylinder and power unit but still need a load cell and a readout and they're pricey. I'll let you guys know when it's done and then do some more break testing.
Takeaway: @moss 's technique is one I'll continue using for myself. Nice job, Andrew!
I'm curious to hear what you guys think so bring it on.
Everything about that picture is beautiful.I'm curious. How exactly are you sewing?
Traditional sewing uses two threads. One is carried through the material by the needle, and a loop is formed on the far side. A second thread from a bobbin is passed through the loop, and it's pulled into the material as the needle goes pack up. The interlocked loops will hold the stitching in place if the thread breaks. A short back stitch will lock the treads in place at the end so a knot isn't needed.
You can also use the needle to push the thread through the material, then grab the thread and pull all of it through. That process is then used from the other side, and repeated over and over until all the thread is used up. The thread needs to be secured with a knot at the end. This method results in more wear on the thread from being pulled through the material over and over.
I expect the special sewing machine used to make professional eye splices is using the traditional method with two threads.
From the picture of the failure of the sewn eye in the black rope in post 746, it looks like friction is doing a pretty good job of holding the threads in place.
It's good to see there's another engineer on the forum, and one who is also a welder/fabricator. This is one of my more challenging projects after retiring from engineering to take up a hobby of welding, fabricating, and machining. It's a saw table for the local steel supply company, complete with rollers on the bed and a roll-out support extension. I also built the table behind the welder in the background.
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Ductaper is using the technique I've detailed in the beginning of this thread and have also updated in the thread as I learned more and refined my technique. It's a long thread ;-)I'm curious. How exactly are you sewing?
Totally agree. I was doing this test to find what would be better than a knot vs. trying to make the joint as strong as possible. Your stitch density seems higher than what I used in the red rope. I was coming at it from a different angle: if all I can use in this rope is a knot, what would be better than it?Interesting to see the two legs of the sewn eye shift during the break test. Typically when my sewn eyes have been pull tested there is no movement in the sewn area or of the two legs of the eye. Since I moved to what I call my "second generation" technique (thorough pre-compression of the two legs before sewing) no one has been able to break any stitching or cause it to shift. The rope always fails first and away from the stitched area.
Your stitch density seems higher than what I used in the red rope.
Here’s the one I used for my big thread, size 25/200: https://www.ebay.com/itm/261513034459@moss or anyone that knows. Got a link to a source for some ball point needles compatible with a Speedy Stitcher, that can accommodate fat thread? I think the thread was called Tec400 or something like that. Also think it said .9mm but that sounds massive, Idk.
I lost mine... I’ll check the haystack but I’m not hopeful.
I had found a link to get them before on this thread but can’t find it now.