I was looking at a rope today and, like all ropes, it was made with strands that are twisted together. I grabbed it and tried to see if it would untwist, and the strands didn’t even separate. So not only do ropes not come untwisted through time and use, you can’t do it if you tried.
So how are they made that they don’t untwist?
Ropes are made of several layers of twisted material. The twist of lower order levels fights against the “untwisting” tendency of higher levels. At the lowest levels, the friction in the individual strands and the interlocking of fibers tends to keep it from untwisting.
Back in Boy Scouts, for the Pioneering merit badge, we had to build rope=-making machines and make our own rope. I’ve since participated in “rope walks” at pioneer recreation-type places.
The ends do tend to unravel if not knotted or whipped.
You know how telephone cords tend to get twisted up? It’s because most people unconsciously turn the receiver in their hands more one way than the other, building up a twist. The same principle applies to spun rope and and fibers: each strand has a twist in it that causes it to form a spiral; and since all the strands are twisted the same way they spiral around each other. To pull a rope apart you need to eliminate the spiraling by untwisting each strand.
Nylon rope is much slipperier than hemp, jute, or cotton, so if it’s not secured at the end (I think nylon is usually fused/melted) it absolutely will untwist itself.
What’s a telephone “cord”?
It’s what you use to charge your phone. Duh!
By no means all ropes consist of strands twisted together. Many are braided, using various schemes including hollow braid, double braid, and kernmantle.
No one mentioned the reverse twist that is used. When making rope or twine you take your bundles and twist the bundle to the right before overlapping the other bundles to the left. I would expect that on a rope they use very hot water to set the twist or steam.
Here is a great video about how modern rope is made:
[quote=“bob_2, post:9, topic:766320”]
Here is a great video about how modern rope is made:
Second video is on chains
Brian
No idea how that happened - Chatham ropewalk:
No need for setting a twist. You start with one strand and twist it. When doubled the two strands will try to untwist themselves, but as they do so they twist together. Except at the ends this is stable.
When I buy rope/line/sheets at the marina store, the first thing I do is whip the ends. If I’m buying nylon lines the salesman melts the ends.
Exactly. You can see the process more clearly in this video - in this case, the device at one end twists the 3 individual strands one way (1:50 in the video). Then the strands are wound around each other in the opposite direction (4:08).
If you didn’t do this, and just take parallel strands and twist them all together, it would quickly become undone.
Whipping and fusing still both tend to come undone, with time. If you really want to secure the end of a rope against fraying, you end-splice it. It takes more time, but it lasts next best thing to forever.