Some pretty good info and straps.

Very cool video! One huge takeaway is do not put knots in your ratchet straps, oh and don't pay attention to the internet "experts" when they spout all their nonsense...
 
Interesting.

I always put one twist to keep the wind from vibrating them. I have had them vibrate so violently that they break over a fairly short time.
 
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Interesting.
My analytical side would like to see 3 samples from each configuration and ensure equal preload...and I'd like to see a more dynamic shock load applied instead of the more slow near static....

I need a bunch of money and just build my own test lab...haha

What does a high speed camera cost?
 
ponykilr said:
Interesting.

I always put one twist to keep the wind from vibrating them. I have had them vibrate so violently that they break over a fairly short time.
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This is something I have never heard of to be honest, but, the proof was there in the one short clip of a trailer going down the road. Not sure if this would help me and my Jeep on a trailer, All four of my straps are pretty short, as in maybe 3-4'. I did see in another video that putting the straps straight vs crossing them is best, and it made sense. Imagine one crossed strap breaking, then, the pressure is not longer crossed, it's one side being pulled the the opposite side. Strap then becomes loose and then the load is not longer secured. Th vid I saw was a simulation, but it made perfect sense.
 
Ron said:
Interesting.
My analytical side would like to see 3 samples from each configuration and ensure equal preload...and I'd like to see a more dynamic shock load applied instead of the more slow near static....

I need a bunch of money and just build my own test lab...haha

What does a high speed camera cost?
Click to expand...
I would like to see more tests as well. 1. bringing the load to near stest breaking point multiple times, 2. strength of strap over a long period of time, and 3. some sort of simulation of road conditions. Vibrations, bumps in the road(shock factor) and even affects of UV's on straps, and hell, a #4, how much is lost with some fraying and or a small cut in the strap.
 
When we moved I had one load of shop stuff including my fairly tall tool box. My neighbor had helped me load everything and was riding with me to unload as well.

I had twisted even the small HF straps one turn and the large 2 and 3” straps as well. He had not twisted one that was holding my “magic bolt bin”, a 4 drawer filing cabinet full of nuts and bolts.

I saw it vibrating wildly and told him why I always put a twist in them. We didn’t make it out of JoCo before it snapped just from vibration. Granted it was a cheap strap but I have had 2” straps fray and break as well. My buddy Dan is who showed me the twist years ago and I have done it ever since.
 
The fact that it breaks at the rachet, makes me wonder if his setup is applying uneven tension across the ram/die. I would have rather him put he strap in straight tension, vs having the bend in the middle. Also, as said, more tests, and a gauge that holds the max load would be nice, vs him guessing. Also, testing different lengths would be interesting.
 
paradisePWoffrd said:
The fact that it breaks at the rachet, makes me wonder if his setup is applying uneven tension across the ram/die. I would have rather him put he strap in straight tension, vs having the bend in the middle. Also, as said, more tests, and a gauge that holds the max load would be nice, vs him guessing. Also, testing different lengths would be interesting.
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From his comments about how warm/hot it was at the break point, there was probably a lot of friction from the overlapping (wound) webbing sliding on itself. It probably overheated at the ratchet.
Would it have broken like that if it was loaded very very slowly so that heat wasn't an issue? Maybe things would have been different.....
As long as the ram is in the middle, so the strap angle is pretty close to the same on both sides, it should be pretty even tension on both sides. If the strap tension came from pulling on one end of the strap instead of loading in the middle with the ram, there could be a lot more variation in tension from one side to the other (change length on one side, plus friction in the middle...). A second load cell (at the other end) would be the easy way to verify what's happening. Or put a roller on the ram, and/or maybe brace it so it can't move off-center if it wants to bend.

The strap is in straight tension. There's nothing constraining the strap ends from rotating on the shackles, so it's a straight pull on the load cell, and the webbing itself can only be loaded in tension. Just like a rope, you can't load a strap in bending or in compression.
The force that the ram is putting into the strap is NOT equal to the strap tension though, because of the strap angle. So if there was a compression load cell on the ram, it would be a very different reading than the tension load cell. I had to watch the video again because I couldn't remember where his load cell was.

Strap length shouldn't matter. Just like rope or a steel bar, tensile strength comes from the section of the strap and not the length of the strap. Longer will stretch more, but the testing in the video is not dynamic so that doesn't matter from energy dissipation or strap weight or whatever other effects.
 
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Fabrik8 said:
From his comments about how warm/hot it was at the break point, there was probably a lot of friction from the overlapping (wound) webbing sliding on itself. It probably overheated at the ratchet.
Would it have broken like that if it was loaded very very slowly so that heat wasn't an issue? Maybe things would have been different.....
As long as the ram is in the middle, so the strap angle is pretty close to the same on both sides, it should be pretty even tension on both sides. If the strap tension came from pulling on one end of the strap instead of loading in the middle with the ram, there could be a lot more variation in tension from one side to the other (change length on one side, plus friction in the middle...). A second load cell (at the other end) would be the easy way to verify what's happening. Or put a roller on the ram, and/or maybe brace it so it can't move off-center if it wants to bend.

The strap is in straight tension. There's nothing constraining the strap ends from rotating on the shackles, so it's a straight pull on the load cell, and the webbing itself can only be loaded in tension. Just like a rope, you can't load a strap in bending or in compression.
The force that the ram is putting into the strap is NOT equal to the strap tension though, because of the strap angle. So if there was a compression load cell on the ram, it would be a very different reading than the tension load cell. I had to watch the video again because I couldn't remember where his load cell was.

Strap length shouldn't matter. Just like rope or a steel bar, tensile strength comes from the section of the strap and not the length of the strap. Longer will stretch more, but the testing in the video is not dynamic so that doesn't matter from energy dissipation or strap weight or whatever other effects.
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I agree that going around the ram shouldnt matter, and that you can only load a strap in tension. However, the strap is multiple layers and woven, and bending across the mandrel on top of the ram is likely butting uneven strain across the strap. Since it is not breaking at that location, the uneven strain on the strap is still within the design parameters. Also, since it isnt a roller, I wonder if the friction from the angle around the mandrel could be causing uneven loading. Again, likely some, but not enough to matter.

I also agree that the breakage at the ratchet is mostly due to heat from the strap continuing to tighten around itself. This brings a point up, does number of wraps around the ratchet matter? I know that you need atleast 1, likely more, to hold the load, but does loading it up help or hurt?

I am also interested in the vibration piece. I think it would be interesting to test the wind speed and direction in relation to the strap and vibration. Length would likely matter, as it would change the resonance frequency of the strap. Also, does tension in the strap matter? If it is more loose or more tight does that matter; I believe it would. And does attaching the excess strap around it change or stop the vibration? I know people dont like to deal with the extra strap length, but what if adding that weight is enough to eliminate the vibration or wear? I could likely dig out some old vibrations calculations and figure it out, but thats not as fun as testing it.
 
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